ImagineNano Abstract Booklet (part I)

On behalf of the International, Scientific and Technical Committees we take great pleasure in welcoming you to Bilbao for the second edition of ImagineNano.

ImagineNano 2013 is now an established event and is considered the largest European in the field. The event is an excellent platform for communication between science and business, bringing together Nanoscience and Nanotechnology in the same place.

Under the same roof will be held 7 International Conferences (Graphene, NanoSpain, nanoBio&Med, PPM, TNA Energy, SPM, nanoSD), a huge Exhibition showcasing cutting-edge advances in nanotechnology research and development, an Industrial Forum and a brokerage event.

Internationally renowned speakers will be presenting the latest trends and discoveries in Nanoscience and Nanotechnology.

We are indebted to the following Scientific Institutions, Companies and Government Agencies for their help and/or financial support: Phantoms Foundation, Donostia International Physics Centre, CIC nanoGUNE, Diputación Foral de Bizkaia, Universidad del País Vasco, Euskampus International Campus of Excellence, AIXTRON, Carl Zeiss Microscopy GmbH, CIC biomaGUNE, Grafoid, Thermo Scientific, Raith GmbH, ICEX Spain Trade and Investment & “españatechnology for life” program, FEDER Funds, FEI, American Elements, Graphenea, Instituto de Bioingeniería de Catalunya, Nanotec Electronica, UAM+CSIC International Campus of Excellence, Universidad Autónoma de Madrid, Centro de Física de Materiales/CSIC, Viajes El Corte Inglés, Basquetour, Nanophotonics for Energy Efficiency Network, Nanoscale Journal, The Catalan Institute of Nanotechnology (ICN), Tecnan/Centro Tecnológico Lurederra, Enterprise Europe Network, Sociedad para la Promoción y Reconversión Industrial (SPRI), Agencia nanobasque, Nanoaracat, Bilbao Exhibition Centre, Innobasque – Agencia Vasca de la Innovación, ARIST /CCIR de Franche-Comté, CSIC- Consejo Superior de Investigaciones Científicas, Grenoble Chamber of Commerce and Industry, Steinbeis Europa-Zentrum and SEIMED. We also would like to thank all participants and exhibitors that joined us this year.

There´s no doubt that ImagineNano 2013 is the right place to see and be seen.

Organisers

Hope to see you again in the next edition of ImagineNano (2015).

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ImagineNano2013 Main Organisers Phantoms Foundation, based in Madrid is a non-profit organization which focus its activities on Nanoscience, Nanotechnology and Emerging Nanoelectronics, bringing together and coordinating the efforts of Spanish and European universities groups, research institutes and enterprises through scientific and technological events, networks and participation in important international events like ImagineNano. Today is a key player in structuring and promoting European excellence and improving collaborations in these fields. It is also essential as a platform for spreading excellence on funded projects and for establishing new networks of collaboration.

The CIC nanoGUNE Consolider is a newly established center created with the mission of addressing basic and applied worldclass research in nanoscience and nanotechnology, fostering high-standard training and education of researchers in this field, and promoting the cooperation among the different agents in the Basque Science, Technology, and Innovation Network (Universities and Technological Centers) and between these agents and the industrial sector.

CIC nanoGUNE has been awarded as the first Consolider Center by the Spanish Education and Science Council. Consolider Centers are created under the Consolider-Ingenio 2010 Program which funds the highest ranked Spanish research consortiums with world-class research lines at the forefront of Science and Technology.

CIC NanoGUNE Consolider represents a necessary step for the promotion of a solid knowledge community with the vocation of transfering the results of reasearch to an industrial sector. A world-class research team, state-of-the-art facilities, close collaboration with other research laboratories and with industry, and a commitment to the society define CIC nanoGune way of understanding scientific research.

The Donostia International Physics Center Foundation (DIPC) was created in 1999, the fruit of institutional collaboration between the Departments of Education and Industry of the Basque government, the University of the Basque Country, the Diputación Foral de Guipúzcoa, the San Sebastián City Hall, the Kutxa of Guipúzcoa and San Sebastián. Iberdrola S.A. also participated in the project from 2000-2003. In 2004, Naturcorp Multiservicios S.A, joined, followed

by Telefónica S.A in 2005.The DIPC was created as an intellectual centre whose main aim is to promote and catalyse the development of basic research and basic research oriented towards material science to reach the highest level. Since its creation, the DIPC has been an open institution, linked to the University of the Basque Country, serving as a platform for the internationalizing of basic science in the Basque Country in the field of materials.

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The University of the Basque Country (UPV/EHU) has been certified 'Campus of International Excellence' by the Spanish Ministry of Education. Alongside the fields of specialization, projects carried out by the research groups result in largely positive numbers and statistics: 171 patents in the last 5 years were requested, so far obtained an 11 million-euro income for transferoriginated activities and produced 1,586 articles in indexed journals in the last 12 months.

The University of the Basque Country is at the helm of Research, Development and Innovation in a region which stands out as one of the most prosperous in Europe. The three campuses are located in the main cities of the Basque Country: Vitoria-Gasteiz (administrative capital of the autonomous community), Bilbao (the biggest city in the region) and San Sebastian.

The University of the Basque Country is a publicly run educational institution that makes every effort to promote knowledge and research, consistently in pursuit of excellence.

45,000 students and a 5,000-membered academic staff are part of this dynamic and bilingual community.

Euskampus: “One University, one Country, one Campus”.

The full development of the Euskampus project, International Excellence Campus, must serve to positionate the UPV/EHU as a reference University internationally speaking, and also to place it in the first positions nationally speaking in 2015.

This project was the product of something leaded by the UPV/EHU in the 2015 University Strategy belonging to the Ministry of Education, whose goals are among others, the modernization and internationalization of the university system and make the university more integrated with its territory at the same time it becomes a key factor for social progress and economic development.

The UPV/EHU, in order to launch this project, has the strategic collaboration of two other knowledge and innovation agents, nationally and internationally speaking. These agents belong to the Basque Country: TECNALIA, Corporación Tecnológica and the Donostia International Physics Center Donostia (DIPC).

Bilbao Exhibition Centre, BEC, is a unique project aimed at bringing people, ideas, economic forces and enterprise together under the same roof. It is a meeting place where technology and innovation work hand in hand in the generation of new business opportunities. As a major promoter of economic, social and cultural development, the BEC has its sights set on becoming one of the world´s leading business centres.

The BEC is also a new concept in its sector, where exhibitors and visitors will benefit from more and improved means of communication. At the BEC, participants will have their own "Personal Trade Consultant" to assist them in any particular needs or formalities. In short, a continuously growing meeting place, always open, where everything is thought for your benefit and where virtually anything is possible.

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ImagineNano2013 Sponsors

Diamond Sponsors

Platinum Sponsors

Gold Sponsors

Bronze Sponsors

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ImagineNano2013 Sponsors

Other Sponsors

Lanyards Sponsors

Grants Sponsors

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Plenary Session

17

Graphene 2013

23

NanoSpain2013

169

nanoBioMed2013

279

PPM2013

389

TNA2013

465

SPM2013

507

NanoSD2013

557

INDUSTRIAL FORUM

584

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General Index

Plenary Session

Index Plenary Session Contributions Pag ■ Alain Aspect (Institut d'Optique / CNRS, France) "Coherent Back Scattering and Anderson Localization of Ultra Cold Atoms"

20

■ John Pendry (Imperial College London, UK)

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19

"Focussing light with surface plasmons, how low can we go?"

Plenary Talk Coherent Back Scattering and Anderson Localization of Ultra Cold Atoms

Alain Aspect

Institut d’Optique, Palaiseau France http://www.lcf.institutoptique.fr/Alain-Aspect-homepage

Ultra cold atoms released in a disordered potential created with a laser speckle, allow one to study Anderson Localization (AL) and Coherent Back Scattering (CBS). Localization has been observed in 1D and 3D, and 2D experiments are promising.

Theory supports the conclusion that what is observed is AL, but a smoking gun of the role of coherence is still missing. Recently, it has been possible to observe CBS (see Figure), an indisputable coherent effect in quantum transport, related to the first order manifestation of localization (weak localization). These experiments belong to the very active domain of simulating difficult problems of Condensed Matter Physics with Ultra-Cold Atoms placed in tailored optical potentials

References

20

[1] J. Billy, V. Josse, Z. C. Zuo, A. Bernard, B. Hambrecht, P. Lugan, D. Clement, L. SanchezPalencia, P. Bouyer, and A. Aspect, "Direct observation of Anderson localization of matter waves in a controlled disorder," Nature 453 (7197), 891-894 (2008).

[2] G. Roati, C. D'Errico, L. Fallani, M. Fattori, C. Fort, M. Zaccanti, G. Modugno, M. Modugno, and M. Inguscio, "Anderson localization of a non-interacting Bose-Einstein condensate," Nature 453 (7197), 895-896 (2008).

[3] Aspect and M. Inguscio, "Anderson localization of ultracold atoms," Physics Today 62 (8), 3035 (2009).

[4] S. S. Kondov, W. R. McGehee, J. J. Zirbel, and B. DeMarco, "Three-Dimensional Anderson Localization of Ultracold Matter," Science 333 (6052), 66-68 (2011).

[5] F. Jendrzejewski, A. Bernard, K. Muller, P. Cheinet, V. Josse, M. Piraud, L. Pezze, L. Sanchez-Palencia, A. Aspect, and P. Bouyer, "Three-dimensional localization of ultracold atoms in an optical disordered potential," Nature Physics 8 (5), 398-403 (2012).

[6] M. Piraud, L. Pezze, and L. Sanchez-Palencia, "Matter wave transport and Anderson localization in anisotropic three-dimensional disorder," Epl 99 (5) (2012).

[7] M. Robert-de-Saint-Vincent, J. P. Brantut, B. Allard, T. Plisson, L. Pezze, L. Sanchez-Palencia, A. Aspect, T. Bourdel, and P. Bouyer, "Anisotropic 2D Diffusive Expansion of Ultracold Atoms in a Disordered Potential," Physical Review Letters 104 (22) (2010).

[8] F. Jendrzejewski, K. Muller, J. Richard, A. Date, T. Plisson, P. Bouyer, A. Aspect, and V. Josse, "Coherent Backscattering of Ultracold Atoms," Physical Review Letters 109 (19) (2012).

Figures

Figure 1: 2D momentum distribution of ultra cold atoms after propagation in a 2D (laser speckle) disordered potential for various propagation times. The first figure shows the initial momentum distribution. One can then see the progressive build up of the ring associated with elastic scattering, and of the Coherent Back Scattering peak still visible after the initial momentum peak has been totally washed out.

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Plenary Talk Focussing light with surface plasmons, how low can we go?

John B Pendry

j.pendry@imperial.ac.uk Department of Physics, Imperial College, London, SW7 2AZ, UK

Nanoscience presents optics with a problem: we cannot see objects smaller than the wavelength using conventional optics. However metals have an unusual property that allows us to get around this problem: when the electric field of a light beam pushes in one direction, the electrons in the metal move in the opposite direction giving a negative value to the permittivity. This gives rise to the phenomenon of surface plasmons, excitations on the metal surface that can be excited by light. Here we show how light can be focussed into length scales much smaller than the wavelength and explore the ultimate limits imposed by the metal.

It turns out that a beam of light can be concentrated into less than a nanometre leading to intense interactions between the energy of the light and individual atoms and molecules.

In this talk I explore how the new technique of transformation optics can give physical insight into the problem of light focussing by plasmons [1]. I shall explore the material properties that limit the extent of the focussing and show a few examples of structures that we propose for this purpose. In most cases analytic solutions can be found and this gives us an understanding of the process that goes far beyond computer simulations. Recent experimental data confirm the validity of our models [2].

Maier, J.B. Pendry, A. Chilkoti, D. R. Smith.

Science 337, 1072-4 (2012).

References

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[1] Transformation optics and subwavelength control of light. J. B. Pendry, A. Aubry, D. R. Smith, S. A. Maier. Science 337, 549-52 (2012).

[2] Probing the Ultimate Limits of Plasmonic Enhancement. C. CiracĂŹ, R. T. Hill, J. J. Mock, Y. Urzhumov, A. I. FernĂĄndez-DomĂ­nguez, S. A.

Graphene 2013

Index Graphene2013 Contributions Keynote ■

Pag

Dimitri Basov (University of California, USA)

42

"Nano - plasmonic phenomena in graphene"

■ Hongjie Dai (Stanford University, USA) "Carbon Nanotubes and Graphene Nanoribbons"

66

■ Andrea Ferrari (University of Cambridge, UK) "Raman Spectroscopy in Graphene and Layered Materials"

■ Bart van Wees

73

(Univ. of Groningen, Netherlands)

"Graphene spintrocics: The current state of the art"

Invited

157

Pag

■ Emilio Artacho (CIC nanoGUNE, Spain) "Density-functional-theory calculations on graphene and related materials"

40

■ Florian Banhart (IPCMS, France) "Electrical conductivity measured in chains of carbon atoms"

41

■ Laszlo P. Biro (Research Inst for Techn Physics and Materials Science, Hungary) 47

"Graphene grain boundaries"

■ Wolfgang Boch (University of California, USA

)

"Status and plans on the FET Flagships"

48

■ Helene Bouchiat (Univ. Paris-Sud 11, France) "Superconducting proximity effect in long superconductor / graphene / superconductor junctions: From specular Andreev reflection at zero field to the quantum Hall regime"

54

■ Antonio Castro Neto (National Univ. of Singapore, Singapore) "New Directions in Materials Science and Technology: Two-Dimensional Crystals"

55

■ Miguel A. Cazalilla (NUS / Graphene Research Center, Singapore) "Kondo Effect and Local Moment Formation in Defective Graphene"

56

■ Hui-Ming Cheng (Inst. of Metal Research, China) "Fabrication and applications of 3D graphene materials"

58

■ Byung Jin Cho (KAIST, Korea) "Application of graphene toward digital electronic device and system"

59

■ Mei-Yin Chou (IAMS - Academia Sinica, Taiwan) "Interacting Dirac Fermions and Neutrino-Like Oscillation in Twisted Bilayer Graphene"

62

■ Luigi Colombo (Texas Instruments, USA)

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63

25

"Graphene Materials, Devices and Integration: Challenges and Opportunities"

Invited

Pag

■ Goki Eda (National Univ. of Singapore, Singapore) 69

"Photoluminescence in two-dimensional crystals"

■ Chris Ewels (IMN- UMR 6502, Nantes, France) "Determining Volume of 2D nanomaterials and Hydrogenated Reconstructed Klein edges"

70

■ Xinliang Feng (Max Planck Inst. for Polymer Research, Germany) 71

"Atomically Precise Synthesis of Graphenes: A Bottom-up Approach"

■ Slaven Garaj (National Univ. of Singapore, Singapore) 81

"Graphene nanopore platform for single-molecule studies"

■ Irina Grigorieva (Univ. of Manchester, UK) 88

"Tuneable magnetism in graphene"

■ Mark Hersam (Northwestern University, USA) 94

"Nanoelectronic Properties and Applications of Chemically Modified Graphene"

■ Ute Kaiser (Ulm University, Germany) "Properties of graphene and other low-dimensional objects obtained from imaging and spectroscopy experiments in a transmission electron microscope"

103

■ Jari Kinaret (Chalmers University of Technology, Sweden) 106

"Graphene Flagship"

■ Tae-Woo Lee (Pohang Univ. of Science and Tech., Postech-Korea) 110

"Graphene Electrodes for Flexible Organic Electronics"

■ Young Hee Lee (Sungkyunkwan University, Korea) 111

"Grain Boundaries in Graphene: Control and Observations"

■ Kian Ping Loh (National Univ. of Singapore, Singapore) 115

"Interesting Properties of Strained or Defective Graphene"

■ João Lopes dos Santos (University of Porto, Portugal) 120

"Continuum Model of the Twisted Bilayer"

■ Francesco Mauri (Univ. Pierre et Marie Curie, France) 124

"How to make graphene superconducting"

■ Arben Merkoçi (ICN, Spain) 125

"Graphene based platforms for biosensing applications"

■ Jannik C. Meyer (University of Vienna, Austria) "New horizons and challenges in the microscopic characterization of 2-D materials"

126

■ Barbaros Ozyilmaz (National Univ. of Singapore, Singapore) "Colossal Enhancement of Spin-Orbit Coupling in Weakly Hydrogenated Graphene"

135

■ Tomas Palacios (MIT, USA) "Atom-Thick Materials for the Next Revolution in Electronics"

136

■ Jiwoong Park (Cornell University, USA) Abstrat not provided by the speaker

-

■ Seongjun Park (Samsung, Korea)

26

"Graphene for Electronic Devices"

137

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Invited

Pag

■ Bernard Placais (LPA - UMR 8551, Paris, France) "Supercollision cooling in undoped graphene"

138

■ Tapani Ryhänen (Nokia Research Center, Finland) "To be defined"

142

■ Kazutomo Suenaga (AIST, Japan) "Atomic Imaging and spectroscopy of defects in low-dimensional materials"

149

■ Peter Sutter (Brookhaven National Lab., USA) "Controlled Synthesis of Heterostructures of 2D Materials"

151

■ Ken Teo (AIXTRON, UK) "Graphene Synthesis, Transfer, FETs and Scaling"

154

■ Jean-Yves Veuillen (Institut NEEL- UPR 2940, Grenoble & UAM, France) "Electronic structure of graphene mono and multilayers on SiC probed by STM"

158

■ Oleg Yazyev (EPFL, Switzerland) "Polycrystalline graphene: atomic structure and electronic transport properties"

163

■ Andrea Young (MIT, USA) "A quantum spin Hall effect in monolayer graphene without time reversal symmetry"

164

■ Amaia Zurutuza (Graphenea, Spain) "Graphene as a potential disruptive material"

Oral

168

Pag

■ Gregory Andreev (Bruker Nano Surfaces, United States) "Enabling the study of nanoscale Graphene physics using nanoconfined, large momentum IR light"

39

■ Salim Berrada (Institut d´Electronique Fondamentale, France) "Graphene Nanomesh Transistors with high on/off ratio"

43

■ Giuseppe Valerio Bianco (IMIP-CNR, Italy) "Controllable n-doping of CVD-graphene by ammonia treatment"

45

■ Peter Bøggild (Technical University of Denmark, Denmark) "Conductance mapping of large-area graphene: a new light on defects"

49

■ Francesco Bonaccorso (Cambridge University, United Kingdom) "Tuning the morphological properties of graphene and 2d crystals in centrifugal fields"

51

■ Andrés Rafael Botello Méndez (UCL, Belgium) "Electronic and transport properties of unbalanced sublattice N-doping in graphene"

52

■ Kitty Cha (BASF SE, Germany) "Graphene Technology Platform at BASF"

57

■ Min Sup Choi (SKKU Advanced Institute of Nano-Technology (SAINT), Korea) "Hysteresis characteristics of hetero-structured devices using two-dimensional materials for memory applications"

61

■ Monica Craciun (University of Exeter, United Kingdom)

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65

27

"All graphene photodetectors"

Oral

Pag

■ Christoph Drexler (University of Regensburg, Germany) 67

"Terahertz-radiation-induced magnetic quantum ratchet effect in graphene"

■ Joaquin Fernandez Rossier (INL, Portugal) 72

"Electronic properties of MoS2-WS2 bilayers"

■ Mauro Ferreira (Trinity College Dublin, Ireland) "Spin-polarized currents in energy-gapped graphene induced by strain-enhanced spin-orbit interaction"

74

■ Gianluca Fiori (University of Pisa, Italy) 75

"Graphene RF Design: what really matters"

■ Rahul Fotedar (Graphene Batteries AS, Norway) 77

"Graphene Enhanced Electrode Performance for Li-ion Batteries"

■ Victor Manuel Freire Soler (Universitat de Barcelona, Spain) "Exploring new ways of chemical vapor deposition technology to produce graphene"

79

■ Wangyang Fu (University of Basel, Switzerland) 80

"CVD graphene and graphene for sensing applications"

■ Bostjan Genorio (Centre of Excellence for Low-Carbon Technologies, Slovenia) 82

"Functionalization of Graphene Nanoribbon Stacks"

■ Khasha Ghaffarzadeh (IDTechEx, United Kingdom) 84

"Graphene- A market perspective"

■ Filippo Giannazzo (CNR-IMM, Italy) "Atomic scale structural and electronic properties of epitaxial graphene on different SiC orientations"

86

■ Ali Hallal (SPINTEC, CEA|CNRS|UJF-Grenoble 1, France) "Proximity Effects Induced in Graphene by Magnetic Insulators: First-Principles Calculations on Spin Filtering and Exchange-Splitting Gaps"

89

■ Ari Harju (Aalto University, Finland) "Contacting atomically well-defined graphene nanoribbons with atomic scale precision"

91

■ Luc Henrard (University of Namur, Belgium) 92

"N-doped graphene: Electronic properties and STM"

■ Stefan Hertel (University of Erlangen-Nuremberg, Germany) "Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics"

95

■ Mario Hofmann (National Cheng Kung University, Taiwan) "A novel class of strain gauges based on layered percolative films of 2D materials"

97

■ Liv Hornekaer (Aarhus University, Denmark) 98

"Probing the Limits of Graphene Metal Coatings"

■ Robert Jacobberger (University of Wisconsin-Madison, United States) 100

"Graphene Crystal Growth Engineering on Epitaxial Copper Thin Films"

■ Frédéric Joucken (University of Namur, Belgium) 102

"Nitrogen doped graphene studied by STM/STS and ARPES"

■ Ladislav Kavan (J Heyrovsky Institute, Czech Republic) "Highly Efficient Electrodes for Dye Sensitized Solar Cells Based on Graphene Oxide"

105

28

■ Arkady Krasheninnikov (Aalto University, Finland)

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Oral "2D Transition-Metal Dichalcogenides: Doping, Alloying and Atomic Structure Engineering Using Electron Beam"

Pag 107

■ Paolo Lacovig (Elettra - Sincrotrone Trieste S.C.p.A., Italy) "Oxygen Switching of the Epitaxial Graphene-Metal Interaction"

108

■ Nicolas Leconte (Université catholique de Louvain, Belgium) "High-Magnetic-Field Conductivity of Chemically Functionalized Graphene: Electron-Hole Symmetry Breaking in the Quantum Hall regime"

109

■ Max Lemme (University of Siegen, Germany) "Graphene Hot Electron Transistors"

113

■ Annick Loiseau (LEM, ONERA-CNRS, France) "Near-band edge optical properties of exfoliated h-BN layers"

116

■ Jean-Nicolas Longchamp (Physics Institute - University of Zurich, Switzerland) "Ultra-Clean Freestanding Graphene by Pt-metal catalysis"

118

■ Mark Lundeberg (ICFO - The Institute of Photonic Sciences, Spain) "Electron spin relaxation and decoherence by magnetic defects in graphene"

121

■ Laurence Magaud (Institut Néel CNRS, France) "Graphene Stacks: a small rotation makes the difference"

122

■ Jens Meyer (Philips Research, Germany) "Organic light emitting diodes using graphene electrodes"

128

■ Thomas Mueller (Vienna University of Technology, Austria) "Ultra-wideband graphene photodetectors for photonic integrated circuits"

130

■ Frank Ortmann (Catalan Institute of Nanotechnology, Spain) "Spin-Relaxation Phenomena in Graphene: Proximity-Induced Spin-Orbit Coupling Yields Novel Type of Ultrafast Spin Relaxation"

132

■ Juerg Osterwalder (Physik-Institut, Universitaet Zuerich, Switzerland) " Growth and Characterization of Graphene / Hexagonal Boron Nitride Heterostack on Cu(111)"

133

■ Deborah Prezzi (CNR, Nanoscience Institute, s3 Center, , Italy) "Electron and Optical Spectroscopies of Graphene Nanoribbons: Insights from Ab-Initio Calculations"

139

■ Juha Riikonen (Aalto University, Finland) "Fabrication of Graphene on Copper Using Photo-Thermal Chemical Vapour Deposition"

141

■ Juan Ramon Sanchez Valencia (EMPA, Swiss Federal Laboratories for Materials Science and Technology, Switzerland) "Atomically precise graphene nanoribbons: Electronic structure, optical properties and vibrational characteristics"

143

■ Daniel Sanchez-Portal (Centro de Fisica de Materiales CFM CSIC-UPV/EHU, Spain) "SAM-like Arrangement of Thiolated Graphene Nanoribbons: Decoupling the Edge State from the Metal Substrate"

145

■ Daniel Schall (AMO GmbH, Germany) "Graphene-based Integrated Circuits: From an Inverter Towards a Ring Oscillator"

146

■ Emmanuel Stratakis (Foundation for Research and Technology Hellas (FORTH), Greece)

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148

29

"Laser photochemical reduction and doping of graphene oxide for organic electronics"

Oral

Pag

■ Mikael Syväjärvi (Graphensic AB, Sweden) 152

"Applications based on graphene on hexagonal and cubic silicon carbide"

■ Klaas-Jan Tielrooij (ICFO - Institut de Ciences Fotoniques, Spain) 155

"Secondary Hot-Carrier Generation in Graphene"

■ Felice Torrisi (University of Cambridge, United Kingdom) 156

"Inkjet-printed 2d crystals"

■ Tim Wehling (University of Bremen, Germany) 160

"Electronic structure of graphene hybrid systems: Screening and interactions"

■ Yuval Yaish (Technion, Israel) 161

"Chemical Potential of Inhomogeneous Single Layer of Graphene"

■ Shou-En Zhu (Delft University of Technology, Netherlands) 165

"Controllable synthesis of large monolayer and multilayer graphene crystals"

■ Igor Zozoulenko (Linköping University, Sweden)

30

"Spin polarization and g-factor enhancement in graphene and graphene nanoribbons in a magnetic field"

166

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Index Graphene2013 Contributions Alphabetical Order I:Invited / K: Keynote / O: Oral

Pag

■ Gregory Andreev (Bruker Nano Surfaces, United States) "Enabling the study of nanoscale Graphene physics using nanoconfined, large momentum IR light"

O

39

I

40

I

41

K

42

O

43

O

45

I

47

I

48

O

49

O

51

O

52

I

54

I

55

I

56

O

57

I

58

I

59

O

61

■ Emilio Artacho (CIC nanoGUNE, Spain) "Density-functional-theory calculations on graphene and related materials"

■ Florian Banhart (IPCMS, France) "Electrical conductivity measured in chains of carbon atoms"

■

Dimitri Basov (University of California, USA) "Nano - plasmonic phenomena in graphene"

■ Salim Berrada (Institut d´Electronique Fondamentale, France) "Graphene Nanomesh Transistors with high on/off ratio"

■ Giuseppe Valerio Bianco (IMIP-CNR, Italy) "Controllable n-doping of CVD-graphene by ammonia treatment"

■ Laszlo P. Biro (Research Inst for Techn Physics and Materials Science, Hungary) "Graphene grain boundaries"

■ Wolfgang Boch (University of California, USA

)

"Status and plans on the FET Flagships"

■ Peter Bøggild (Technical University of Denmark, Denmark) "Conductance mapping of large-area graphene: a new light on defects"

■ Francesco Bonaccorso (Cambridge University, United Kingdom) "Tuning the morphological properties of graphene and 2d crystals in centrifugal fields"

■ Andrés Rafael Botello Méndez (UCL, Belgium) "Electronic and transport properties of unbalanced sublattice N-doping in graphene"

■ Helene Bouchiat (Univ. Paris-Sud 11, France) "Superconducting proximity effect in long superconductor / graphene / superconductor junctions: From specular Andreev reflection at zero field to the quantum Hall regime"

■ Antonio Castro Neto (National Univ. of Singapore, Singapore) "New Directions in Materials Science and Technology: Two-Dimensional Crystals"

■ Miguel A. Cazalilla (NUS / Graphene Research Center, Singapore) "Kondo Effect and Local Moment Formation in Defective Graphene"

■ Kitty Cha (BASF SE, Germany) "Graphene Technology Platform at BASF"

■ Hui-Ming Cheng (Inst. of Metal Research, China) "Fabrication and applications of 3D graphene materials"

■ Byung Jin Cho (KAIST, Korea) "Application of graphene toward digital electronic device and system" "Hysteresis characteristics of hetero-structured devices using two-dimensional materials for memory applications"

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■ Min Sup Choi (SKKU Advanced Institute of Nano-Technology (SAINT), Korea)

I:Invited / K: Keynote / O: Oral

Pag

■ Mei-Yin Chou (IAMS - Academia Sinica, Taiwan) "Interacting Dirac Fermions and Neutrino-Like Oscillation in Twisted Bilayer Graphene"

I

62

I

63

O

65

K

66

O

67

I

69

I

70

I

71

O

72

K

73

O

74

O

75

O

77

O

79

O

80

I

81

O

82

O

84

O

86

I

88

O

89

■ Luigi Colombo (Texas Instruments, USA) "Graphene Materials, Devices and Integration: Challenges and Opportunities"

■ Monica Craciun (University of Exeter, United Kingdom) "All graphene photodetectors"

■ Hongjie Dai (Stanford University, USA) "Carbon Nanotubes and Graphene Nanoribbons"

■ Christoph Drexler (University of Regensburg, Germany) "Terahertz-radiation-induced magnetic quantum ratchet effect in graphene"

■ Goki Eda (National Univ. of Singapore, Singapore) "Photoluminescence in two-dimensional crystals"

■ Chris Ewels (IMN- UMR 6502, Nantes, France) "Determining Volume of 2D nanomaterials and Hydrogenated Reconstructed Klein edges"

■ Xinliang Feng (Max Planck Inst. for Polymer Research, Germany) "Atomically Precise Synthesis of Graphenes: A Bottom-up Approach"

■ Joaquin Fernandez Rossier (INL, Portugal) "Electronic properties of MoS2-WS2 bilayers"

■ Andrea Ferrari (University of Cambridge, UK) "Raman Spectroscopy in Graphene and Layered Materials"

■ Mauro Ferreira (Trinity College Dublin, Ireland) "Spin-polarized currents in energy-gapped graphene induced by strain-enhanced spin-orbit interaction"

■ Gianluca Fiori (University of Pisa, Italy) "Graphene RF Design: what really matters"

■ Rahul Fotedar (Graphene Batteries AS, Norway) "Graphene Enhanced Electrode Performance for Li-ion Batteries"

■ Victor Manuel Freire Soler (Universitat de Barcelona, Spain) "Exploring new ways of chemical vapor deposition technology to produce graphene"

■ Wangyang Fu (University of Basel, Switzerland) "CVD graphene and graphene for sensing applications"

■ Slaven Garaj (National Univ. of Singapore, Singapore) "Graphene nanopore platform for single-molecule studies"

■ Bostjan Genorio (Centre of Excellence for Low-Carbon Technologies, Slovenia) "Functionalization of Graphene Nanoribbon Stacks"

■ Khasha Ghaffarzadeh (IDTechEx, United Kingdom) "Graphene- A market perspective"

■ Filippo Giannazzo (CNR-IMM, Italy) "Atomic scale structural and electronic properties of epitaxial graphene on different SiC orientations"

■ Irina Grigorieva (Univ. of Manchester, UK) "Tuneable magnetism in graphene"

■ Ali Hallal (SPINTEC, CEA|CNRS|UJF-Grenoble 1, France) "Proximity Effects Induced in Graphene by Magnetic Insulators: First-Principles Calculations on Spin

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Filtering and Exchange-Splitting Gaps"

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■ Ari Harju (Aalto University, Finland) "Contacting atomically well-defined graphene nanoribbons with atomic scale precision"

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■ Luc Henrard (University of Namur, Belgium) "N-doped graphene: Electronic properties and STM"

■ Mark Hersam (Northwestern University, USA) "Nanoelectronic Properties and Applications of Chemically Modified Graphene"

■ Stefan Hertel (University of Erlangen-Nuremberg, Germany) "Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics"

■ Mario Hofmann (National Cheng Kung University, Taiwan) "A novel class of strain gauges based on layered percolative films of 2D materials"

■ Liv Hornekaer (Aarhus University, Denmark) "Probing the Limits of Graphene Metal Coatings"

■ Robert Jacobberger (University of Wisconsin-Madison, United States) "Graphene Crystal Growth Engineering on Epitaxial Copper Thin Films"

■ Frédéric Joucken (University of Namur, Belgium) "Nitrogen doped graphene studied by STM/STS and ARPES"

■ Ute Kaiser (Ulm University, Germany) "Properties of graphene and other low-dimensional objects obtained from imaging and spectroscopy experiments in a transmission electron microscope"

■ Ladislav Kavan (J Heyrovsky Institute, Czech Republic) "Highly Efficient Electrodes for Dye Sensitized Solar Cells Based on Graphene Oxide"

■ Jari Kinaret (Chalmers University of Technology, Sweden) "Graphene Flagship"

■ Arkady Krasheninnikov (Aalto University, Finland) "2D Transition-Metal Dichalcogenides: Doping, Alloying and Atomic Structure Engineering Using Electron Beam"

■ Paolo Lacovig (Elettra - Sincrotrone Trieste S.C.p.A., Italy) "Oxygen Switching of the Epitaxial Graphene-Metal Interaction"

■ Nicolas Leconte (Université catholique de Louvain, Belgium) "High-Magnetic-Field Conductivity of Chemically Functionalized Graphene: Electron-Hole Symmetry Breaking in the Quantum Hall regime"

■ Tae-Woo Lee (Pohang Univ. of Science and Tech., Postech-Korea) "Graphene Electrodes for Flexible Organic Electronics"

■ Young Hee Lee (Sungkyunkwan University, Korea) "Grain Boundaries in Graphene: Control and Observations"

■ Max Lemme (University of Siegen, Germany) "Graphene Hot Electron Transistors"

■ Kian Ping Loh (National Univ. of Singapore, Singapore) "Interesting Properties of Strained or Defective Graphene"

■ Annick Loiseau (LEM, ONERA-CNRS, France) "Near-band edge optical properties of exfoliated h-BN layers"

■ Jean-Nicolas Longchamp (Physics Institute - University of Zurich, Switzerland) "Ultra-Clean Freestanding Graphene by Pt-metal catalysis" "Continuum Model of the Twisted Bilayer"

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■ João Lopes dos Santos (University of Porto, Portugal)

I:Invited / K: Keynote / O: Oral

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■ Mark Lundeberg (ICFO - The Institute of Photonic Sciences, Spain) "Electron spin relaxation and decoherence by magnetic defects in graphene"

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■ Laurence Magaud (Institut Néel CNRS, France) "Graphene Stacks: a small rotation makes the difference"

■ Francesco Mauri (Univ. Pierre et Marie Curie, France) "How to make graphene superconducting"

■ Arben Merkoçi (ICN, Spain) "Graphene based platforms for biosensing applications"

■ Jannik C. Meyer (University of Vienna, Austria) "New horizons and challenges in the microscopic characterization of 2-D materials"

■ Jens Meyer (Philips Research, Germany) "Organic light emitting diodes using graphene electrodes"

■ Thomas Mueller (Vienna University of Technology, Austria) "Ultra-wideband graphene photodetectors for photonic integrated circuits"

■ Frank Ortmann (Catalan Institute of Nanotechnology, Spain) "Spin-Relaxation Phenomena in Graphene: Proximity-Induced Spin-Orbit Coupling Yields Novel Type of Ultrafast Spin Relaxation"

■ Juerg Osterwalder (Physik-Institut, Universitaet Zuerich, Switzerland) " Growth and Characterization of Graphene / Hexagonal Boron Nitride Heterostack on Cu(111)"

■ Barbaros Ozyilmaz (National Univ. of Singapore, Singapore) "Colossal Enhancement of Spin-Orbit Coupling in Weakly Hydrogenated Graphene"

■ Tomas Palacios (MIT, USA) "Atom-Thick Materials for the Next Revolution in Electronics"

■ Jiwoong Park (Cornell University, USA) Abstrat not provided by the speaker

■ Seongjun Park (Samsung, Korea) "Graphene for Electronic Devices"

■ Bernard Placais (LPA - UMR 8551, Paris, France) "Supercollision cooling in undoped graphene"

■ Deborah Prezzi (CNR, Nanoscience Institute, s3 Center, , Italy) "Electron and Optical Spectroscopies of Graphene Nanoribbons: Insights from Ab-Initio Calculations"

■ Juha Riikonen (Aalto University, Finland) "Fabrication of Graphene on Copper Using Photo-Thermal Chemical Vapour Deposition"

■ Tapani Ryhänen (Nokia Research Center, Finland) "To be defined"

■ Juan Ramon Sanchez Valencia (EMPA, Swiss Federal Laboratories for Materials Science and Technology, Switzerland) "Atomically precise graphene nanoribbons: Electronic structure, optical properties and vibrational characteristics"

■ Daniel Sanchez-Portal (Centro de Fisica de Materiales CFM CSIC-UPV/EHU, Spain) "SAM-like Arrangement of Thiolated Graphene Nanoribbons: Decoupling the Edge State from the Metal Substrate"

■ Daniel Schall (AMO GmbH, Germany)

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"Graphene-based Integrated Circuits: From an Inverter Towards a Ring Oscillator"

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■ Emmanuel Stratakis (Foundation for Research and Technology Hellas (FORTH), Greece) "Laser photochemical reduction and doping of graphene oxide for organic electronics"

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■ Kazutomo Suenaga (AIST, Japan) "Atomic Imaging and spectroscopy of defects in low-dimensional materials"

■ Peter Sutter (Brookhaven National Lab., USA) "Controlled Synthesis of Heterostructures of 2D Materials"

■ Mikael Syväjärvi (Graphensic AB, Sweden) "Applications based on graphene on hexagonal and cubic silicon carbide"

■ Ken Teo (AIXTRON, UK) "Graphene Synthesis, Transfer, FETs and Scaling"

■ Klaas-Jan Tielrooij (ICFO - Institut de Ciences Fotoniques, Spain) "Secondary Hot-Carrier Generation in Graphene"

■ Felice Torrisi (University of Cambridge, United Kingdom) "Inkjet-printed 2d crystals"

■ Bart van Wees

(Univ. of Groningen, Netherlands)

"Graphene spintrocics: The current state of the art"

■ Jean-Yves Veuillen (Institut NEEL- UPR 2940, Grenoble & UAM, France) "Electronic structure of graphene mono and multilayers on SiC probed by STM"

■ Tim Wehling (University of Bremen, Germany) "Electronic structure of graphene hybrid systems: Screening and interactions"

■ Yuval Yaish (Technion, Israel) "Chemical Potential of Inhomogeneous Single Layer of Graphene"

■ Oleg Yazyev (EPFL, Switzerland) "Polycrystalline graphene: atomic structure and electronic transport properties"

■ Andrea Young (MIT, USA) "A quantum spin Hall effect in monolayer graphene without time reversal symmetry"

■ Shou-En Zhu (Delft University of Technology, Netherlands) "Controllable synthesis of large monolayer and multilayer graphene crystals"

■ Igor Zozoulenko (Linköping University, Sweden) "Spin polarization and g-factor enhancement in graphene and graphene nanoribbons in a magnetic field" "Graphene as a potential disruptive material"

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■ Amaia Zurutuza (Graphenea, Spain)

A b s t r a ct s Alphabetical order

Graphene 2013

Oral Enabling the study of nanoscale Graphene physics using nanoconfined, large momentum IR light

Gregory Andreev S. Minne

Bruker Nano Surfaces Division, Santa Barbara, California, United States

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References

GRAPHENE 2013

[1] G.O. Andreev, et al. "Extraordinary sensitivity of nanoscale infrared spectroscopy demonstrated on Graphene and thin SiO2", Bulletin of the American Physical Society, (Oral Presentation on 3/22/2011).

[2] Z Fei, et al. "Gate-tuning of graphene plasmons revealed by infrared nanoimaging", Nature 487, 82-85 (2012).

[3] Chen, J. et al. “Optical nano-imaging of gatetunable graphene plasmons”, Nature 487, 77-81 (2012).

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Mid-infrared light confined to nanoscale volumes is a powerful and versatile probe of Graphene physics. For instance, recent IR-sSNOM experiments show that one can excite, image, and spectrally characterize Dirac plasmons in Graphene with nanoscale sensitivity1,2,3. Due to the uncertainty principle: Δx Δk ≥ 0.5, conventional IR microscopy lacks both the spatial momentum and spatial resolution necessary to launch and simultaneously image such surface waves.

In the IR-sSNOM technique, nanoconfinement of IR light between a sharp metallic tip (<10nm radius) and the sample surface can reduce Δx to <10nm and consequently increase Δk by as much as 3 orders of magnitude over the diffraction limited value.

The IR frequency of the excitation, however, remains unchanged. Beyond the recently demonstrated plasmonic applications, we believe the potential for using IR light with such a large spatial momentum is not yet fully recognized by the Graphene community. In this work, we demonstrate yet another consequence of the extremely large Δk of naconfined IR light: ultrasensitivity to Graphene thickness. We show this phenomenon experimentally with high resolution (<20nm) IR sSNOM images which clearly show monotonically increasing contrast for 1,2,3, 4 Graphene layers. We confirmed the layer number by colocalized confocal Raman and high resolution AFM measurements. Our proof of principle experiment confirms a 3D sensitivity for nanoconfined IR light to be better than 20 x 20 x 0.35nm for single to multilayer Graphene samples.

Invited Density-functional-theory calculations on graphene and related materials

Emilio Artacho

e.artacho@nanogune.eu Nanogune and DIPC, Tolosa Hiribidea 76, 20018 San Sebastián, Spain Basque Foundation for Science, Ikerbasque, 48011 Bilbao, Spain Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom

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Some recent results of first-principles calculations of graphene-related materials will be reviewed.

The calculations are based on density-functional theory (DFT) using the Siesta method. From early calculations of the phonon spectra of graphene and nanotubes [1], to calculations of bilayer graphene nanoribbons [2], the calculations demanded the possibility of efficient simulations with large number of atoms, as implemented in Siesta, which is capable of linear-scaling DFT calculations, i.e. calculations whose cost in CPU and memory scale linearly with the number of atoms in the unit cell, as opposed to the conventional cubic scaling of canonical DFT. In many situations related to graphene and derivatives, Van der Waals interactions are crucial. The very efficient recent implementation [3] of the fully first-principles, fully non-local density functional proposed in 2004 [4] and its variants [5-7] have allowed more accurate simulations of bilayer graphene, both for the mentioned ribbons [2] and for the study of divacancy defects in bilayer graphene motivated by electron microscopy findings [8]. Similar large scale calculations have also allowed the supporting of results obtained more formally for insulating compounds in the graphene-like honeycomb structure and their heterostructures [9]. Effective fractional charges of e/3 are found as fundamental charge in the polarization discontinuity at the interface between two of such insulators, the origin of such well-defined charges being in many ways analogous to what found in symmetry protected topological phases (the two insulators at each side of the interface corresponding to different symmetry-defined values of the Berry-phase associated to polarization). This is analogous to the physics

behind [10] the two-dimensional electron gases appearing at interfaces between some perovskite materials [11], and one-dimensional gases proposed at steps of such interfaces [12]. In graphenic insulators, one-dimensional electron gases should also appear, which have a high probability of being half metallic (metallic for one spin direction only) [9].

References [1] D. Sánchez-Portal, E. Artacho, J.M. Soler, A. Rubio and P. Ordejón, Phys. Rev. B 59 (1999) 12678.

[2] H. Santos, A. Ayuela, L. Chico and E. Artacho, Phys. Rev. B 85 (2012) 245430.

[3] G. Román-Pérez and J. M. Soler, Phys. Rev. Lett.

103 (2009) 096102.

[4] M. Dion, H. Rydberg, E. Schröder, D.C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92 (2004) 246401.

[5] K. Lee, E.D. Murray, L. Kong, B.I. Lundqvist, D.C. Langreth, Phys. Rev. B 82 (2010) 081101.

[6] J. Klimeš, D.R. Bowler and A. Michaelides, J. Phys.: Condens. Matter 22 (2010) 022201.

[7] O.A. Vydrov and T. van Voorhis, Phys. Rev. Lett.

103 (2009) 063004.

[8] J. Zubeltzu, A. Chuvilin and E. Artacho, in preparation (see Poster).

[9] N.C. Bristowe, M. Stengel, P. B. Littlewood, E. Artacho, and J. M. Pruneda, arXiv:1210.2278.

[10] N.C. Bristowe, P.B. Littlewood & E. Artacho, J. Phys. Condens. Matter, Viewpoint 23 (2011) 081001.

[11] A. Ohtomo and H. Y. Hwang, Nature 427 (2004) 423-426.

[12] N. C. Bristowe, T. Fix, M. G. Blamire, P. B. Littlewood & E. Artacho, Phys. Rev. Lett. 108 (2012) 166802.

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Invited Electrical conductivity measured in chains of carbon atoms

1

Florian Banhart 1 O. Cretu 2 A. R. Botello-Mendez I. Janowska3, C. Pham-Huu3 and 2 J.-C. Charlier

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Institut de Physique et Chimie des Matériaux, UMR 7504, Université de Strasbourg, florian.banhart@ipcms.unistra.fr 23 rue du Loess, 67034 Strasbourg, France 2 Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Chemin des étoiles 8, 1348 Louvain-la-Neuve, Belgium 3 Laboratoire des Matériaux, Surfaces et Procédés pour la Catalyse, UMR 7515 CNRS, 25 rue Becquerel, 67087 Strasbourg, France

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The work has been funded by the French Agence Nationale de Recherche (NT09 507527, NANOCONTACTS) and by the F.R.S.-FNRS of Belgium. This research is directly connected to the ARC on Graphene StressTronics sponsored by the Communaute Francaise de Belgique.

References [1] O. Cretu, A. R. Botello-Mendez, I. Janowska, C. Pham-Huu, J.-C. Charlier, F. Banhart, arXiv 1302.5207.

GRAPHENE 2013

Contacts between transition metal tips and graphitic deposits were established while an electrical bias was applied between the two components. By slowly retracting the tip, graphene ribbons were pulled out of the deposit.

Occasionally, chains of carbon atoms were seen to unravel from the graphenic material so that an atomic chain spanned between the electrodes.

The observed chains had lengths of up to 10 – 15 atoms and lifetimes of some seconds under observation in the electron beam of the TEM. This allowed the monitoring of the current through the system and the measurement of currentvoltage curves during their observation. The formation of the chains was accompanied by a characteristic drop in conductivity of the system.

The overall conductivity of the chains on the order 10-7 – 10-9 A at applied voltages up to 1 V was much lower than predicted theoretically for an unperturbed chain. Comparison with DFT and many-body perturbation theory shows that both the contact resistivity and strain in the chains determine their conductivity. Strain transforms the chain from cumulene, with double bonds throughout the chain, to polyyne with alternating single-triple bonds. Furthermore, the strain has a

decisive influence on the bandgap of the chain.

This is also indicated by different I/V-curves resulting from measurements on different chains.

A unique cumulene or polyyne configuration is unlikely to exist due to varying strain and the stabilization of dimerization under stress.

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As strings of monoatomic thickness, chains of sp1hybridized carbon atoms constitute the logical one-dimensional phase of carbon. They have been proposed theoretically since a long time until they have been observed in electron microscopy studies. However, electrical measurements on these monoatomic chains have not been feasible.

Now, by using a measuring system with an STM tip in a TEM specimen stage, we were able not only to produce carbon chains but also to pass a current through them and so to measure their electrical properties for the first time [1].

Keynote Nano - plasmonic phenomena in graphene

Dimitri N. Basov

dbasov@ucsd.edu University of California San Diego http://infrared.ucsd.edu/

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GRAPHENE 2013

Infrared nano-spectroscopy and nano-imaging experiments have uncovered rich optical effects associated with the Dirac plasmons of graphene [Nano Lett. 11, 4701 (2011)]. We were able to directly image Dirac plasmons propagating over sub-micron distances [Nature 487, 82 (2012)]. We have succeeded in altering both the amplitude and wavelength of these plasmons by gate voltage in common graphene/SiO2/Si back-gated structures.

We investigated losses in graphene using scanning plasmon interferometry: by exploring real space profiles of plasmon standing waves formed between the tip of our nano-probe and edges of the samples. Plasmon dissipation quantified through this analysis is linked to the exotic electrodynamics of graphene [Nature-Physics 4, 532 (2008), PRL 102, 037403 (2009)]. Scanning plasmon interferometry has allowed us to visualize grain boundaries in CVD graphene. These experiments revealed that grain boundaries tend to form electronic barriers that impede both electrical transport and plasmon propagation. Our results attest to the feasibility of using electronic barriers to realize tunable plasmon reflectors. Finally, we have carried out pump-probe experiments probing ultra-fast dynamics of plasmons in exfoliated graphene with the nano-scale spatial resolution.

ImagineNano2013

Oral Graphene Nanomesh Transistors with high on/off ratio

1

Salim Berrada 2 V. Hung Nguyen 1 D. Querlioz J. Saint-Martin1 1 A. Bournel 1 C. Chassat and 1 P. Dollfus

1

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the Green's function approach to solving a tightbinding Hamiltonian, self-consistently coupled to 3D Poisson's equation [12]. Various GNM lattices have been considered as schematized in Fig. 1a, differing in the x and y neck widths (Wx and Wy) and filling factors. A 3D view of the simulated GNM-FETs is shown in Fig. 1b, with a gate length LG = 30 nm and infinite width thanks to appropriate periodic boundary conditions along y direction. The results were compared to the case of pristine graphene FET (GFET). For the GNM lattice characterized by Wx 1.1 nm / Wy 1.2 nm and an anti-filling factor AFF of 13.3%, the bandgap reaches 553 meV. For the transistor based on this GNM we plot in Fig. 2 the local density of states (for ky = 0) at the Dirac point (VGS = 0.2 V) and the corresponding transmission function. The bandap widely overlaps the current transmission window [Efd, Efs], which results in a low off-current of 0.72 ÎźA/Îźm.

The ID-VGS characteristics of four devices are plotted in Fig. 3 for VDS = 0.2 V. In addition to the previous device, we consider also the case of pristine graphene (EG = 0), a GNM with Wx 2.3 nm, Wy 2.2 nm and AFF = 10% (EG = 268 meV) and a GNM with Wx 1 nm, Wy 1.1 nm and AFF = 6.25% (EG = 508 meV). It appears clearly that when increasing the bandgap the off-current is reduced. However, the highest bandgap of 553 meV does not provide the highest on/off ratio.

Indeed, for this GNM, the rather high AFF of 13.3% tends to degrade significantly the oncurrent. In spite of a slightly higher off-current the device with the GNM bandgap of 508 meV offers a much higher on-current thanks to a smaller AFF and finally an on/off ratio of 1460 twice as high as for the GNM with EG = 553 meV. It is remarkably better than the performance of

GRAPHENE 2013

Though the excellent transport properties of pristine graphene [1,2] gave rise to a lot of expectations towards high performance electronics, the possible range of applications of graphene transistors (GFET) turned out to be rather limited by the gapless character of this material. Indeed, the lack of bandgap yields a very small on/off current ratio and a poor saturation behaviour [3,4]. To open a bandgap in graphene, a possible approach consists in cutting graphene layers into nanorribons (GNRs) but fabricating narrow-enough (sub-3 nm) ribbons with good edge roughness control remains challenging. It is also possible to open a bandgap of about 130 meV in bilayer graphene by applying a strong electric field perpendicular to the bilayer plane [5], which allows enhancing the on/off ratio of transistors up to 100 at 300 K [6]. Recently, the fabrication of a new graphene nanostructure called graphene nanomesh (GNM) has been reported [7]. It consists in generating a regular array of antidots separated by a sub-10 nm distance. According to the periodicity and the neck width of GNM lattice, bandgaps of several hundreds of meV have been predicted to appear in large sheets of graphene [8,9]. A similar result can be obtained in superlattices of graphane-like islands formed by patterned adsorption of hydrogen atoms [10]. This kind of bandgap nanoengineering offers new possibilities to design improved devices delivering large currents. For instance, GNM-based PN junctions have been predicted to exhibit a negative differential conductance with high peak-to-valley ratio [11].

In the present work, we investigate GNM-based field-effect transistors (GNM-FETs) by means of 3D numerical simulation. The model is based on

salim.berrada@u-psud.fr

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Institute of Fundamental Electronics, Univ. Paris-Sud, CNRS, Orsay, France Institute of Nanosciences and Cryogenics, L_Sim, SP2M, UMR-E CEA/UJF, Grenoble, France 2

pristine GFET. This work shows that the GNM-FET offers a promising way of improving the performance of graphene transistors, which will be discussed in detail.

Figures

References [1] K.I. Bolotin et al., Solid-State Com 146 (2008) 351-355.

[2] P.J. Zomer, S.P. Dash, N. Tombros, and B.J. van Wees, Appl. Phys. Lett. 99 (2011) 232104.

[3] Ph. Avouris, Nano Lett.10 (2010) 4285â&#x20AC;&#x201C;4294.

[4] I. Meric et al., Nature nanotechnol.3 (2008) 654-659.

[5] J.B. Oostinga et al., Nat. Mater. 7 (2008) 151157.

[6] F. Xia, D.B. Farmer, Y.-M. Lin, and Ph. Avouris, Nano Lett., 10 (2010) 715-718.

[7] J. Bai, X. Zhong, S. Jiang, Y. Huang and X. Duan, Nat. Nanotechnol. 5 (2010) 190-194.

[8] T.G. Pedersen et al., Phys. Rev. Lett. 100 (2008) 136804.

[9] V. Hung Nguyen, M. Chung Nguyen, H. Viet Nguyen, P. Dollfus, J. Appl. Phys. 113 (2013) 013702.

[10] R. Balog et al., Nature Mater. 9 (2010) 315319.

[11] V. Hung Nguyen, F. Mazzamuto, J. SaintMartin, A. Bournel, P. Dollfus, Nanotechnology 23 (2012) 065201.

[12] V. Hung Nguyen, F. Mazzamuto, A. Bournel, and P. Dollfus, J. Phys. D 45 (2012) 325104 (2012).

Figure 1: (a) Typical view of a GNM lattice characterized by the neck widths Wx and Wy. (b) Schematic 3D view of the GNM-FET. The gate length is LG = 30 nm, the BN gate insulator thickness is 2 nm.

Figure 2: (left panel) Local density of states for k y = 0 in a GNMFET for VDS = VGS =0.2 V. The potential profile at the center of the device is superimposed (white line). (right panel) Corresponding transmission function. GNM considered: Wx = 1.1 nm, Wy = 1.2 nm and AFF = 13.3%.

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Figure 3: ID-VGS characteristics of simulated devices at VDS = 0.2 V (see text for details on GNM parameters).

ImagineNano2013

Oral Controllable n-doping of CVDgraphene by ammonia treatment

Institute of Inorganic Methodologies and of Plasmas, CNR-IMIP, Chemistry Department of University of Bari “Aldo Moro”, Via Orabona 4, 70126 Bari, Italy

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giuseppevalerio.bianco@cnr.it

of chemical doping on the charge carriers density (n=1/Rxxeµ) and mobility (µ=Rxy/RxxB). We demonstrate that ammonia adsorption is sensitive to functional groups and defects on the CVD-graphene surface such as epoxyl, idroxyl or carbonyl groups at defects and grain edges [3].

Specifically, a direct correlation between the degree of n-doping and the oxidation degree of different graphene samples has been found.

In order to evaluate the stability of the achieved chemical n-doping and to provide a better understanding of graphene/ammonia interaction, the effect of temperature on the ammonia adsorption and desorption processes was also investigated. Experimental data attest for different adsorption configurations of ammonia on graphene characterized by different interaction strengths [4]. In particular, the role of temperature in promoting reactive interaction of ammonia with defects and functionalities on CVD graphene is demonstrated.

[1] Yanbin An, Ashkan Behnam, Eric Pop, and Ant Ural,. Applied Physics Letters 102 (2013) 013110.

[2] Sokrates T. Pantelides, Yevgeniy Puzyrev, Leonidas Tsetseris, and Bin Wang, MRS BULLETIN, 37 (2012) 1187.

[3] Shaobin Tang and Zexing Cao, J. Phys. Chem.

C, 116 (2012) 8778.

[4] Yong-Hui Zhang, Ya-Bin Chen, Kai-Ge Zhou, Cai-Hong Liu, Jing Zeng, Hao-Li Zhang and Yong Peng, Nanotechnology 20 (2009) 185504.

GRAPHENE 2013

References

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The unique transport and optical properties of graphene find interesting applications in optoelectronics such as transparent conductive electrode substituting ITO and as active electrode in Schottky junctions with conventional semiconductors [1]. Unlike conventional metal electrodes, graphene allows the modulation of the Schottky barrier since its work function can be tailored by electrostatic gating or chemical doping. Several doping methodologies have been studied and, currently, it is more challenging to achieve stable n-doped graphene than the easily obtained p-doped one (with the exception of epitaxial graphene that is intrinsically ndoped)[2].

This contribution focuses on the n-doping of CVDgraphene by ammonia treatments. In contrast to substitutional doping, the proposed “postgrowth” doping methodology exploits charge transfer from adsorbed ammonia that allows the Fermi level modulation without important effect on carriers mobility. The degree of charge transfer between graphene and adsorbed ammonia as well as the strength of this interaction (chemisorption or physisorption) are still under debate as demonstrated by the many theoretical and experimental studies reported in literature. Thus, the main aim of this work is to evaluate the feasibility of ammonia treatment for achieving effective and stable n-doping.

Ammonia adsorption on graphene was studied by real time monitoring of graphene sheet resistance (Rxx) upon exposure to high NH3 pressures. To point up how high electron-doping affects graphene electronic properties, complementary measurements of Hall resistance (Rxy) in magnetic field (B) were also carried out.

This provided a direct evaluation of the influence

Giuseppe V. Bianco M. Losurdo M. M. Giangregorio A. Sacchetti P. Capezzuto and G. Bruno.

Figures

Time

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Figure 1: Real time monitoring of Sheet resistance (Rxx) and Hall resistance (Rxy) for a CVD graphene transferred on glass upon annealing at 200째C in vacuum and subsequent ammonia exposure.

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Invited 1, 4

Graphene grain boundaries 1

Institute of Technical Physics and Materials Science, Centre for Natural Sciences, 1525 Budapest, PO Box 49, Hungary, http://www.nanotechnology.hu/ 2 Center for Nano-metrology Division of Industrial Metrology Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Republic of Korea 3 Center for Nanocharacterization, Division of Industrial Metrology, Korea Research Institute of Standards and Science, Yuseong, Daejeon 305-340, Republic of Korea 4 Korean-Hungarian Joint Laboratory for Nanosciences (KHJLN), P.O. Box 49, 1525 Budapest, Hungary 5 Department of Physics of Matter and Radiations, University of Namur (FUNDP), 61 Rue de Bruxelles, B-5000 Namur, Belgium

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References

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[1] L. P. Biró & Ph. Lambin, New J. Phys. 15, 035024 (2013).

[2] J. Cervenka & C. Flipse, Phys. Rev. B 79, 195429 (2009).

[3] L. Tapasztó et al., Appl. Phys. Lett. 100, 053114 (2012).

[4] S. Kurasch et al., Nano Lett., 12, 3168 (2012).

[5] P. Nemes-Incze et al., Appl. Phys. Lett. 99, 023104 (2011).

[6] J. Koepke et al., ACS nano, 7, 75 (2013).

[7] J. Kotakoski & J. C. Meyer, Phys. Rev B 85, 195447 (2012).

[8] P. Nemes-Incze et al., under review in Carbon.

[9] P. Vancsó et al. under review in Carbon.

[10] P. Simonis et al., Surf. Sci. 511, 319 (2002).

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Grain boundaries (GBs) in CVD graphene have a crucial role in defining the properties of large graphene sheets [1] important from the point of view of practical applications. Given the very large variety of the CVD conditions used: low pressure to atmospheric pressure, solid, or molten substrate, and a wide range of growth temperatures and gas mixtures used for growing CVD graphene on copper, GBs of very different structure may be produced. Some further points have to be observed concerning the structural differences of the GBs in graphene obtained by cleavage from bulk graphite (HOPG, or natural) [2] and CVD grown graphene [3]. The possible influences of the e-beam irradiation during HRTEM observation of GBs in CVD grown graphene [4] cannot be neglected. Therefore STM [3] and AFM [5] are very versatile and convenient tools for the investigation of graphene GBs both in the as-grown state on the Cu substrate and after transfer to SiO2 [6].

The CVD grown GBs may contain significant disorder [1,7]. While the exact structural details of such disorder cannot be easily revealed by experimental techniques, the combination of experimental data with careful computer simulation may reveal the characteristic properties even for disordered GBs [8,9]. The impact of disorder on charge transport through GBs is very clearly illustrated if comparing the transmission through an ordered (5-7) GB [10] and through an disordered GB: in the range -2 to 2 eV the transmission probability through the disordered GB is reduced to one third.

The atomic scale information on the structure and formation of GBs will be reviewed and compared to computer simulation results on graphene GB structure and properties.

Laszlo P. Biró 1, 4 P. Nemes-Incze 2, 4 1, 4 X. Jin , P. Vancsó L. Tapasztó1, 4, G. I. Márk1, 4 3, 4 5 Y. S. Kim Ph. Lambin and 2, 3 C. Hwang

Invited Status and plans on the FET Flagships

Wolfgang Boch

European Commission Directorate General for Communication Networks, Content and Technology Head of Flagships Unit

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FET Flagships are a new concept in the Horizon 2020 EU research and innovation programme.

Flagships are a new scheme under the Future and Emerging Technologies part of the Excellent Science pillar of H2020. They are designed to tackle grand scientific and technological challenges requiring a common European effort.

Flagships are conceived as science-driven, largescale, multidisciplinary research initiatives targeting transformational impacts on science and technology, and bringing substantial benefits for European competitiveness and society.

Flagships will create a critical mass of research actors to boost EU research and innovation and to enable better coherence of national and EU actions. They aim to establish EU leadership and breakthroughs in key technology areas of high impact to the economy and society. Due to their ambitious goals and high degree of multidisciplinarity they require cooperation across a range of disciplines, communities and programmes, as well as financial support of longer duration than the typical EU R&D project life-cycle of 2-4 years. They will be based on partnerships that enable effective coordination of efforts.

An initial very competitive process for the selection of ideas, followed by an extensive preparation phase for six candidate Flagships led to the refinement of their vision and goals and the elaboration of detailed strategic roadmaps for the six topics. In 2012 a Call was launched for fully-fledged Flagship proposals addressing the six finalist topics, which has led to the selection of two FET Flagships, to be launched in 2013. The two Flagships are now currently in contract negotiation and are expected to start working in

autumn this year. Each Flagship is expected to be granted about 54 M€ EU funding for a "ramp-up" phase of the Flagships for the first 30 months.

The overall vision is that these two Flagships will run for a 10 year period, during which the total budget will reach around 1Bn€.

The selected Flagship GRAPHENE aims to take graphene and related materials from a state of raw potential to a point where it can revolutionize multiple industries – from flexible, wearable and transparent electronics to high performance computing, spintronics and composite materials.

The other selected Flagship THE HUMAN BRAIN PROJECT is aiming at the understanding of the human brain, which will lead to fundamentally new computing technologies, transform the diagnosis and treatment of brain diseases, and providing profound insights into our humanity.

The presentation will highlight the role, the main characteristics and the research policy dimension pursued by the FET Flagship scheme, as well as the extended role of Future and Emerging Technologies in the context of the next EU's Framework Programme on Research and Innovation.

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Oral Conductance mapping of large-area graphene: a new light on defects 1

Department of Micro- and Nanotechnology, Technical University of Denmark, Kgs. Lyngby, 2 Department of Photonics Engineering, Technical University of Denmark, Kgs. Lyngby, Denmark 3 Department of Physics, McGill University, Montréal, Québec, Canada H3A 2T8 4 Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg,Sweden 5 Capres A/S, Diplomvej, Building 373, DK-2800 Kongens Lyngby, Denmark 6 CINF, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark

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1

J. D. Buron1,2, D. H. Petersen1 M. Møller2, M. B. B. Larsen1 D. MacKenzie1, F. Pizzochero1 T. J. Booth1, D. G. Cooke3 M. Hilke3, J. Sun4 E. Whiteway3, P. F. Nielsen5 O. Hansen1,6, A. Yurgens4 and P. Uhd Jepsen2

Peter.Boggild@nanotech.dtu.dk

References [1] ] Buron, Jonas Christian Due; Petersen, Dirch Hjorth; Bøggild, Peter; Cooke, David G.; Hilke, Michael; Sun, Jie; Whiteway, Eric; Nielsen, Peter F.; Hansen, Ole; Yurgens, August; Jepsen, Peter Uhd, Nano Letters, 12 (2012), 5074.

GRAPHENE 2013

sensitive, respectively. This is supported by geometrical sample analysis possible with M4PP dual configuration measurements.

From the four-point resistance ratio RA/RB (where the RA configuration is defined as I:V:V:I and RB as I:V:I:V), it is possible to distinguish between samples, where the current transport is essentially 1D and 2D, respectively (Fig. 2). We show that for a continuous graphene film without defects or with defects, that have a spatial extend far smaller than the electrode pitch, the sample should behave as a 2D conductive film with RA/RB=1.265, whereas a highly damaged but still coherent film will give exactly RA/RB=1. This nonintuitive result is experimentally verified with great accuracy in our measurements. The discovery has the intriguing consequence that a statistical comparison of sheet conductance measured at different length-scales with the geometrical "foot-print" extracted from the RA/RB ratio allows for direct, parameter-free evaluation of both the defect density and the characteristic length scale of the defects.

Finally, we demonstrate that THz conductance mapping using a backgate highlights disconnected or damaged areas of CVD graphene, and discuss to which degree such optically derived conductance curves can be directly compared with electrical gate sweeps (Fig. 3).

49

We overview recent progress in analysing the conducting properties of large-area graphene by comparing several contact and non-contact mapping techniques. We combine three independent sheet conductance mapping techniques for detailed characterization of single layer graphene at different length-scales (λ), providing a consistent methodology for evaluating the electrical conductance and electrical defect distribution of large-area graphene[1]. Whereas terahertz time-domain spectroscopy (THz-TDS) maps the nanoscale conductance (λ ~ 10-100 nm) averaged over the beam spot size, spreading resistance probe (SRP) maps the sub-μm local conductance (λ ~ 1001000 nm) and variable pitch micro four-point probe (M4PP) the micro-scale conductance (λ ~ 1100 μm) (Fig. 1). The technique has been used successfully on up to 5 x 5 cm graphene samples.

These three inherently different sheet conductance mapping techniques have been applied for detailed characterization of centimeter-scale single layer graphene, grown by copper catalyzed CVD technique and transferred onto Si substrates coated with 90 nm SiO2. With more than 4000 individual measurement positions measured by each method we are able to conduct a statistical correlation analysis for the three techniques involved. We find a qualitative good agreement between the mean sheet conductance values measured with the three different techniques in areas of the graphene film that appear free from optically visible damage.

However, in certain areas of the graphene film the measured sheet conductance, GS, is dependent on the measurement technique such that GS,M4PP < GS,SRP < GS,THz. Evidently this must be related to μm-scale and sub-μm-scale defects for which the M4PP and SRP methods are

Peter Bøggild

Figures

Figure 1: Combination of Raman spectroscopy, THz time-domain spectroscopy, spreading resistance measurements (SRP) and micro four point measurement (M4PP) yields information on conducting properties across scales ranging from sub-nanometer to millimetre scale.

Figure 2: The ratio of resistances measured in A and B configuration is highly sensitive to the local integrity of the graphene sheet, with RA/RB = 1.26 corresponding to the limit of inifinite 2D graphene, and RA/RB = 1.00 corresponding to a 1D or 1D/2D dimensionality due to for instance cracks, rips, domain boundaries or other macroscale defects.

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Figure 3: THz conductance mapping of a graphene sheet for different applied gate voltages using a moderately to low doped silicon substrate as a back gate, allows large-area, non-contact identification of connected/active and disconnected/inactive areas. The top contacts are present to allow direct comparison with conventional electrical conductance measurements.

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Oral Tuning the morphological properties of graphene and 2d crystals in centrifugal fields

1,2

Francesco Bonaccorso 1 1 F. Torrisi , C. Russo 1 1 G. Privitera , M. Bruna T. Hasan1, V. Nicolosi3 4 N. Pugno and 1 A.C. Ferrari

1

Cambridge Graphene Centre, University of Cambridge, Cambridge CB3 0FA, UK CNR-IPCF V.le Stagno D'Alcontres 37, 98158, Messina, Italy School of Chemistry, School of Physics & CRANN Trinity College Dublin Dublin 2 Ireland 4 Department of Civil, Environmental and Mechanical Engineering, University of Trento, Italy 2 3

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References [1] F. Bonaccorso et al. Materials today, 15 (2012) 564.

[2] Y. Hernandez et al. Nature Nanotech., 3 (2008) 563.

[3] T. Hasan, et al. Phys. Status Solidi B 247 (2010) 2953.

[4] F. Torrisi, et al., ACS Nano, 6 (2012) 2992.

[5] A. A. Green et al, Nano Lett. 9 (2009) 4031.

[6] M. S. Arnold et al., Nature Nanotech. 1 (2006) 60.

[7] F. Bonaccorso et al., Journal of Physical Chemistry C 114 (2010) 17267.

[8] M. K. Brakke, Arch. Biochem. 45, (1953), 275.

[9] O.M. Maragoâ&#x20AC;&#x2122; et al., ACS Nano, 4 (2010) 7515.

[10] F. Bonaccorso et al., Nature Photonics 4 (2010) 611.

[11] J.N. Coleman et al. Science 331 (2011) 568.

Figure 1: Sorting of layered materials (MoS2) via RZS. (a) Formation of step gradient by placing a density gradient medium with decreasing concentration. (b) During RZS flakes with different sedimentation coefficient will travel along the cuvette at different sedimentation velocities. This will cause a spatial separation along the cuvette between smaller and larger flakes. (c) Photograph of cuvette containing sorted MoS2 after RZS. (d) TEM images of flakes extracted along the cuvettele.

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Figures

51

We show how to produce graphene flakes with controlled morphological properties, via low power sonication of graphite in sodium deoxycholate (SDC) followed by ultracentrifugation. There are two main approaches to ultracentrifugation [1]: sedimentation-based separation (SBS) [2,3,4] and density gradient ultracentrifugation (DGU) [5].

The former discriminates particles by their difference in mass. The latter exploits density differences between particles in a density gradient medium (DGM) [6,7]. If the ultracentrifugation is stopped before the particles achieve their isopycnic point, i.e. the point where the particles match the density of the DGM, a rate zonal separation (RZS) is achieved [8]. RZS is based on difference in masses and shapes of particles in the centrifugal field [8]. Indeed, particles with different masses and shapes will move with different sedimentation velocity along the DGM [8]. We exploit SBS to separate graphite flakes by number of layers [9,10], achieving a yield of ~65% monolayers, with~600nm2 average size [9,10]. Isopycnic separation allows us to obtain larger flakes than SBS. Surfactants provide this density variation [5], with a 60% yield of monolayers in the top fraction, with~1Îźm2 size.

Inorganic layered materials [11], such as Boron Nitride, Tungsten Disulfide, Molybdenum Disulfide, etc., have a density that cannot be supported by common DGMs, thus cannot be separated via isopycnic separation. We show here how to obtain dispersions with controlled lateral size via RZS, see Fig.1.

fb296@cam.ac.uk

Oral Electronic and transport properties of unbalanced sublattice N-doping in graphene

Andrés R. Botello-Méndez A. Lherbier and J - C. Charlier

andres.botello@uclouvain.be

Université catholique de Louvain, IMCN-NAPS, Chemin des étoiles 8, 1348 Louvain-la-neuve, Belgium

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The incorporation of foreign atoms into the carbon honeycomb lattice has been widely investigated in order to modify the electronic and chemical properties of graphene [1,2]. In contrast with conventional materials, the effect of foreign atoms in a 2D material, such as graphene, is expected to depend significantly on the position and surrounding of each atom due to the quantum confinement of the electrons [2].

Recent scanning tunneling microscopy and spectroscopy studies of nitrogen doped graphene have revealed how the incorporation of this foreign atom into the sp2 lattice occurs. Joucken and coworkers showed that the exposure of graphene to a nitrogen plasma flux after synthesis leads to an homogeneous distritution of substitutional atoms [3]. However, when a nitrogen source is introduced during the CVD growth of graphene, the nitrogen incorporation exhibits a preferential accommodation within one of the two triangular sublattice that compose the honeycomb lattice [4,5]. This wayward incorporation of nitrogen atoms into graphene is not hitherto understood. Nevertheless, the consequences of this peculiar atom arrangement on the electronic and transport properties of graphene are adressed in this work.

Electronic structure and transport properties of nitrogen-doped graphene with a single sublattice preference are investigated using both firstprinciples techniques and a real-space KuboGreenwood approach. Such a break of the sublattice symmetry leads to the appearance of a true band gap in graphene electronic spectrum. A band gap opening due to an ordered superlattice of dopants has already been discussed [6,7].

However, such a periodic doping configuration is rather difficult to envisage experimentally. In this

work, we demonstrate the robustness of the band gap opening for the case of a random distribution of dopants in the same sublattice. In addition, a natural spatial separation of both types of charge carriers at the band edge is observed, leading to a highly asymmetric electronic transport. For such N-doped graphene systems, the carriers at the conduction band edge present outstanding transport properties with long mean free paths, high conductivities and mobilities. This phenomena is explained by a nondiffusive regime, and originates from a low scattering rate. The fact that corresponding electrons reside mainly in the unaltered sublattice explains such low scattering rate.

The presence of a true band gap along with the pesistence of carriers traveling in an unperturbed sublattice suggest the use of such doped graphene in GFET applications, where a high ION/IOFF ratio is needed. The present simulations should encourage more investigation and specific measurements on N-doped graphene samples where such an unbalanced sublattice doping has been observed.

References [1] P. Ayala, R. Arenal, A. Loiseau, A. Rubio, and T. Pichler, Rev. Mod. Phys. 82 (2010) 1843.

[2] Z M. Terrones, A. Filho, A. Rao. Doped Carbon Nanotubes: Synthesis, Characterization and Applications in Carbon Nanotubes Springer (2008) 531.

[3] F. Joucken, Y. Tison, J. Lagoute, et al. Phys.

Rev. B 85 (2012) 161408(R).

[4] L. Zhao, R. He, K.T. Rim et al., Science 333 (2011) 999.

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[5] R. v, . i, A.R. Botello-M ende et al., Nature Scientific Reports 2 (2012) 586.

[6] R. Martinazzo, S. Casolo, and G.F. Tantardini, Phys. Rev. B 81 (2010) 245420.

[7] S. Casolo, R. Martinazzo, and G.F. Tantardini, J. Phys. Chem. C 115 (2011) 3250.

[8] A. Lherbier, A. R. Botello-MĂŠndez, J.-C. Charlier (submitted).

Figures

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Figure 1: STM images of nitrogen doped graphene obtained by incorporation of N during growth: (a) single substitution [4], and (b) double substitution [5]. (c) Calculated semiclassical conductivities in graphene for various concentrations of N dopants randomly distributed in one sublattice [8].

Invited Superconducting proximity effect in long superconductor / graphene / superconductor junctions: From specular Andreev reflection at zero field to the quantum Hall regime

Helene Bouchiat C. Li, K. Komatsu S. Autier-Laurent and S. Gueron

Laboratoire de Physique des Solides UMR 8502 Universite Paris Sud, 91405 Orsay cedex, France

A superconductor-graphene(SG) hybrid system, such as an SGS junction or an SG interface, provides an ideal platform to investigate the relativistic nature of Dirac fermions combined with superconductivity. Instead of the retroreflection of carriers in an ordinary superconductor-normal metal interface, an SG interface is theoretically predicted to show the specular reflection of quasiparticle carriers.

We show that a supercurrent flows through a SGS junction with Nb electrodes even through a very long graphene distance of 1.2 micron, more than 3 times the length previously reported. This supercurrent disappears in the vicinity of the Dirac point, indicating a strong sensitivity of the transmission of Andreev pairs to the formation of charge puddles with size greater than the superconducting coherence length.

We also present data on similar size graphene samples with superconducting electrodes with a high critical field (more than 7Tesla) for which the properties of the normal state are dominated by quantum Hall physics. Whereas the behavior of the supercurrent is similar to the Nb/Graphene/Nb system in zero field, new features are observed in the high field quantum Hall regime.

Figures

Figure 1: Sketch of the superconducting proximity effect through diffusive graphene, at high and low doping. (Top) Highly doped regime. The usual Andreev retroreflection at the S/G interface leads to diffusive counterpropagation with zero total phase accumulation. (Bottom) Low-doping regime. SpecularAndreev reflection of propagating Andreev pairs can occur at an n/0 or p/0 junction, leading to loss of counterpropagation and thus large phase accumulation within an Andreev pair. Supercurrent, which results from all Andreev trajectories, is destroyed. The red region is electron doped, the blue one is hole doped, and the green region in between has nearly zero doping.

References

54

[1] Katsuyoshi Komatsu, Chuan Li, S. AutierLaurent, H. Bouchiat, S. GuĂŠron Phys. Rev. B 88, 115412 (2012).

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Invited New Directions in Materials Science and Technology: Two-Dimensional Crystals

Antonio H. Castro Neto

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Smart advanced materials that are flexible (for transparent wearable electronics), adaptable (that change structure depending on exterior conditions), multifunctional (that can be tuned by application of electric and magnetic fields, pressure or strain), and at the same time are environmentally friendly (that do not waste energy and are low power consuming), are the ultimate dream of materials scientists and engineers. Such materials hold the key to the next generation of devices with deep incursions into new markets. The discovery of graphene and other twodimensional crystals in 2004 has finally brought materials with the promise of such properties to light. More importantly, the recent breakthrough in their industrial scale fabrication is paving the way towards a new era in materials science and technology. A shift in such a key economic sector will provide unprecedented opportunities in transforming the industry with impact in several fundamental areas: energy, defense, communications, electronics, artificial intelligence, and information technology. I will describe the latest developments, the opportunities, and future challenges in this new field and the plans at the Graphene Research Centre at the National University of Singapore to develop and study, theoretically and experimentally, a large family of advance materials, which do not exist in nature (and certainly are not yet available commercially) with new functionalities that can meet the needs of an ever-demanding market.

GRAPHENE 2013

Director, Graphene Research Centre National University of Singapore, Singapore Professor of Physics, Boston University, USA

Invited Kondo Effect and Local Moment Formation in Defective Graphene

Miguel A. Cazalilla A. Iucci F. Guinea and A. H. Castro Neto

Graphene Research Centre, National University of Singapore, Singapore, Centro de Fisica de Materiales (CFM) Centro Mixto CSIC UPV, and Donostia International Physics Center (DIPC), San Sebastian, Spain

miguel.cazalilla@gmail.com

We study the local moment formation and the Kondo effect at single-atom vacancies in Graphene. We develop a model accounting for the vacancy reconstruction as well as nonplanarity effects induced by strain and/or temperature. Thus, we find that the dangling $\sigma$ orbital localized at the vacancy is allowed to strongly hybridize with the $\pi$-band since the scattering with the vacancy turns the hybridization into singular function of the energy ($\sim [|\epsilon| \ln^2 \epsilon/D]^{-1}$, $D\sim$ the bandwidth). This leads to several new types of impurity phases, which control the magnitude of the vacancy magnetic moment and the possibility of Kondo effect depending on the strength of the local Coulomb interactions, the doping level, and the degree of particlesymmetry breaking

References

56

[1] M. A. Cazalilla et al. arxiv: 1207.3135.

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Oral Graphene Technology Platform at BASF

Kitty C. Cha M. G. Schwab and S. S. Venkataraman

BASF SE, Ludwigshafen, Germany

kitty.cha@basf.com

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GRAPHENE 2013

At BASF, graphene and graphene materials are currently being studied for several potential fields of application. We have established a Graphene Technology Platform aiming at the systematic investigation of this new carbon material fabricated either by top-down or bottom-up procedures.

Owing to its appealing electrical conductivity, graphene can be used for conductive formulations and coatings as well as for polymer composite materials with antistatic properties. Also, graphene may serve as a new carbon material thus replacing or complementing traditional carbon black additives in lithium-ion batteries as well as activated carbons in supercapacitor devices. It is also intended to evaluate graphene-based transparent conductive layers for their use in displays, organic solar cells and organic light emitting diodes. A new joint Carbon Materials Innovation Center with the Max Planck Institute for Polymer Research has been inaugurated, with the purpose of exploring these themes. The talk will focus on the recent activities of BASF in the field of graphene and provide an evaluation of this promising material from an industrial point of view

Invited Fabrication and applications of 3D graphene materials

Hui-Ming Cheng

cheng@imr.ac.cn Advanced Carbon Division, Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences Shenyang 110016, China

58

There are great challenges of how to realize largescale fabrication of high-quality graphene structures and large-size single crystal graphene domains, which are essential for mass applications and device applications. In recent two years, in order to obtain graphene in a relatively large quantity by chemical vapor deposition, we tried to use Ni particles [1] and Ni foams [2] as substrates.

Interestingly, with a Ni foam as template, a threedimensional (3D) graphene macrostructure, which we called graphene foam (GF), has been synthesized [2]. This porous graphene bulk material consists of an interconnected network of graphene, is flexible, and has outstanding electrical and mechanical properties. And it can be used in elastic conductors [2], sensors [3], flexible lithium ion batteries [4], and electromagnetic interference fielding materials [5]. Using this unique network structure and the outstanding electrical and mechanical properties of GFs, we demonstrate the great potential of GF/PDMS composites for flexible, foldable and stretchable conductors, and parts-per-million level detection of NH3 and NO2 in air at room-temperature by this GF, which can also rival the durability and affordability of traditional sensors. By using GF as a current collector, loaded with Li4Ti5O12 and LiFePO4, for use as anode and cathode, respectively, we fabricated a thin, lightweight, and flexible full lithium ion battery, with a high-rate performance and energy density that can be repeatedly bent to a radius of 5 mm without structural failure and performance loss.

Finally, we prepared an ultra-lightweight and graphene-based foam composite with high EMI shielding performance and the graphene/PDMS foam composite shows excellent flexibility, and its shielding effectiveness is almost unchanged after

repeatedly being bent to a radius of ~2.5 mm for 10,000 times.

Acknowledgements: Financial support from NSFC, MOST and CAS is acknoledged.

References [1] Z. P. Chen, et al, Bulk growth of mono- to fewlayer graphene on nickel particles by chemical vapor deposition from methane, Carbon 48 (12), 2010, p.3543-3550.

[2] Z. P. Chen, et al, Three-dimensional flexible and conductive interconnected graphene networks grown by chemical vapour deposition, Nature Materials 10, 2011, p. 424428.

[3] F. Yavari, Z. P. Chen, et al, High senstitivity gas dection using a macroscopic threedimensional graphene network, Scientific Reports 1 166 2011, DOI: 10.1038/srep00166.

[4] N. Li, et al, Lightweight and flexible graphenebased lithium ion batteries with ultrafast charge and discharge rates, PNAS, 109 (43), 2012, 17360-17365.

[5] Z. P. Chen, et al, Lightweight and flexible graphene foam composites for highperformance electromagnetic interference shielding, Adv Mater 2013, in press.

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Invited Application of graphene toward digital electronic device and system

1

Byung Jin Cho 1 Seul Ki Hong and 1 Jeong Hun Mun

bjcho@kaist.edu 1

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20-fold reduction relative to the theoretical limitation of conventional metal-oxidesemiconductor (MOS) devices. The proposed device structure demonstrates the feasibility of bringing graphene into the mainstream of semiconductor device technology with minimal changes to current MOS device technology but with substantial improvement in device performance.

(2) Reliability of high-K gate dielectric is one of the most serious concerns in deep scaled CMOS devices for both digital logic and memory device applications. We demonstrate that the high-k gate dielectric reliability is dramatically improved by replacing metal gate electrode with graphene gate electrode. The atomic-scale thickness and flexible nature of graphene completely eliminate mechanical stress in the high-k gate dielectric, resulting in significant reduction of trap generation in the high-k film. Almost all the electrical properties related to reliability of MOSFET such as the positive-bias temperature instability (PBTI), time-dependent dielectric breakdown (TDDB) (Fig. 2), leakage current, etc are significantly improved [2]. Data retention and program/erase properties of charge trap Flash memory are also greatly improved when graphene is used as a gate electrode of the charge trap Flash memory device [3]. As the graphene gate electrode does not require stringent control of defects in graphene, the graphene gate electrode can easily be adopted to the CMOS front-end line, by using variety of graphene synthesis methods including solutionbased process and so on. Therefore, the result in this work pioneers the way for the adoption of the new nano-material to conventional CMOS devices to overcome the limitation of the performance and reliability of the current devices in production.

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In this talk, applications of graphene for digital electronic devices are presented in three different ways; a channel material of FET, a gate electrode of FET, and an electromagnetic interference (EMI) shielding material.

(1) Graphene, which presents remarkably high electron mobility, has come to the forefront as an alternative channel material for the post-silicon era. However, the natural lack of an energy bandgap hinders the practical use of graphene field effect transistor (FET) devices, especially for digital logic applications. Extensive efforts have accordingly been made to open up the energy bandgap of graphene. However, the bandgap and carrier mobility are in a trade-off relationship in most materials. Once the energy bandgap is opened in graphene, its original physical properties are altered and carrier mobility degradation is unavoidable. It is also unrealistic to attain a bandgap of larger than 0.4 eV, which is the minimum practical requirement for digital circuit applications. Here, we propose a new device structure that does not require opening the bandgap of graphene and therefore can fully utilize the original unique properties of graphene.

The new device employs a physical gap along the channel instead of opening grapheneâ&#x20AC;&#x2122;s energy bandgap as shown in Fig. 1, and is designed with consideration of producibility and compatibility to conventional complementary-MOS (CMOS) process technology [1]. The physical-gap-channel graphene transistor is implemented on a siliconon-insulator (SOI) substrate. The device simulation results of the newly proposed device structure reveal successfully suppressed off-state current of ~10-9 A/Âľm, an on/off current ratio of more than seven orders of magnitude, and a subthreshold slope of 2.23 mV/decade, constituting more than a

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Dept. of Electricla Engineering, KAIST, 291 Dawhak-ro, Yuseong-gu Daejeon 305-701 South Korea

(3) We report the first experimental results on the EMI shielding effectiveness (SE) of wafer-scale monolayer graphene [4]. The prepared monolayer CVD graphene has an average SE value of 2.27 dB, corresponding with ~ 40% shielding of incident waves. CVD graphene shows more than 7 times (in terms of dB) greater SE than gold film. The dominant mechanism is absorption rather than reflection, and the portion of absorption decreases with an increase of the number of graphene layers.

Our modeling work shows that plane-wave theory for metal shielding is also applicable to graphene.

The model predicts that ideal monolayer graphene can shield as much as 97.8% of EMI. This suggests the feasibility of manufacturing an ultrathin, transparent, and flexible EMI shield by single or few-layer graphene. As the graphene is found to be an excellent EMI shielding material, it is also successfully applied to 3D IC with mixed signal system as a shielding material.

Figures

Figure 1: Schematic drawing of the physical-gap-channel graphene transistor. The graphene channel under the gate is physically separated from the source edge. The source is p+ doped, while the drain is n+ doped. The silicon body is almost intrinsic. A high-κ spacer is used to induce a fringing electric field to the silicon surface.

References

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[1] J.H. Mun and B.J. Cho, "Physical-Gap-Channel Graphene Field Effect Transistor with High On/Off Current Ratio for Digital Logic Applications", Appl. Phys. Lett, vol. 101, (2012) p. 143102.

[2] J. K. Park, S. M. Song, J. H. Mun, and B. J. Cho, "Dramatic Improvement of high-K Gate Dielectric Reliability by Replacing Metal Gate Electrode with Mono-Layer Graphene", 2012 Symposium on VLSI Technology, Hawaii, USA, June 12-15, (2012).

[3] J. K. Park, S. M. Song, J. H. Mun, and B. J. Cho, “Graphene Gate Electrode for MOS StructureBased Electronic Devices”, Nano ett., vol. 11, no.12, (2011) p. 5383.

[4] S. K. Hong, K. Y. Kim, T. Y. Kim, J. H. Kim, S. W. Park, J. H. Kim, and B. J. Cho, "ElectroMagnetic Interference (EMI) Shielding Effectiveness of Monolayer Graphene", Nanotechnol., vol. 23, no. 45, (2012) p.

455704.

Figure 2: Time dependent dielectric breakdown (TDDB) property of the devices with two different gate electrodes. Time-to-breakdown of graphene gate device is more than two orders of magnitude higher.

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Oral Hysteresis characteristics of heterostructured devices using twodimensional materials for memory applications 1

SKKU Advanced Institute of Nano-Technology (SAINT), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon, Korea 2 Columbia University, 10027 New York, USA 3 Electronics and Telecommunications Research Institute (ETRI), 218 Gajeong-ro, Yuseong-gu, Daejeon, Korea

[1] Britnell, L. et al., Science, 335 (2012) 947950.

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[2] Georgiou, T. et al. Nat. Nanotech., 8 (2013) 100-103.

[3] Yu, W. J. et al. Nat. Materials, (2012) doi: 10.1038/nmat3518.

[4] Lee, G. â&#x20AC;&#x201C;H. et al. Appl. Phys. Lett., 99, (2011) 243114.

Figures

Figure 1: (a) Transfer curve (ID-VG) and (b) Retention performance of the GBM device with hBN of 6 nm and MoS2 of 5 nm. The inset of (a) shows a transfer curve of GB (Graphene/hBN). (c) Transfer curve and (d) Retention performance of the MBG device with hBN of 12 nm, MoS2 of 3 layers, and graphene of 2 layers. The inset of (c) shows a transfer curve of the same device when graphene was used for gating.

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References

goodcms@skku.edu

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Recently, various hetero-structured devices using two-dimensional materials have been developed due to its high performances and flexibility.[1]-[3] In this work, the ultrathin memory devices consisting of two-dimensional (2D) materials were fabricated by stacking graphene, hexagonal boron nitride (hBN), and molybdenum disulfide (MoS2), demonstrating large memory window and good retention properties as shown in Figure 1. The two different device structures of, graphene/hBN/MoS2 (GBM) and MoS2/hBN/graphene (MBG), where graphene and MoS2 were employed as channel and charge trap layer for GBM and vice versa for MBG, were investigated. Even though both device structures exhibit a large hysteresis, their field effect transistor (FET) characteristics are quite different. The large hysteresis for memory application can be induced by quantum tunneling effect through the thin hBN layer (< 10 nm) and charge trapping in underlying 2D layer.[1],[4] By formation of the potential wells in the underlying MoS2 or graphene layers between SiO2 and hBN dielectrics, the charges can tunnel through ultrathin hBN layer and be effectively trapped or released depending on the applied gate voltages. We observed that these trapped charge can be maintained in potential wells and this induces the significant hysteresis in the current - voltage transfer curves of the 2D FETs. These results provide a promising way to fabricate memory devices using 2D materials.

1

Min Sup Choi 2 2,3 G. - H. Lee , Y. - J. Yu 1 1 D. - Y. Lee , S. H. Lee P. Kim2, J. Hone2 and 1 W. J. Yoo

Invited 1, 2

Interacting Dirac Fermions and Neutrino-Like Oscillation in Twisted Bilayer Graphene

Mei-Yin Chou 1 Lade Xian 1. 3 Zhengfei Wang meiyin.chou@physics.gatech.edu

1

School of Physics, Georgia Tech, Atlanta 30332, USA Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan Department of Materials Science and Engineering, University of Utah, Salt Lake City 84112, USA 2 3

It has become possible in recent years to fabricate and manipulate two-dimensional nanomaterials in the laboratory that are as thin as one to few atomic layers. A well-known example is graphene, where the Dirac-Weyl Hamiltonian for massless fermions describes the low-energy quasiparticles.

Intriguing physics has been found in these fewlayer systems, and phenomena originally associated with particle physics can now be observed in condensed matter systems. In this talk, I will focus on our recent theoretical and computational studies of a few representative systems. In particular, the quasiparticle states in rotated bilayer graphene systems act as massless fermions with two “flavors”, and interlayer coupling induces neutrino-like oscillations and anisotropic transport. The mixing between layer states and energy eigenstates due to interlayer coupling in twisted bilayer graphene is responsible for such oscillatory behavior. The quasi-particle oscillation takes place in a specific energy window in which wave packet transport is anisotropic.

These two-dimensional atomic layer systems provide a unique platform to probe the rich physics involving multiple interacting massless fermions

Figures

Figure 1: Schematic illustration of interlayer interaction in twisted bilayer graphene. (a) A plane cutting through the Dirac points of the two Dirac cones associated with the two twisted layers. The energy bands on the cross section shown in (a) are drawn in (b) and (c) for cases without and with interlayer interaction, respectively. (d) A plane cutting through the two Dirac cones without including the two Dirac points. The energy bands on the cross section shown in (d) are drawn in (e) and (f) for cases without and with interlayer interaction, respectively.

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Figure 2: Electronic structure of twisted bilayer graphene with a twisted angle of 7.34°. (a) Band structure calculated by a tight binding model. The strong coupling energy region is highlighted by a blue dashed box. (b) Band contour of the top two valence bands in the first Brillouin zone. (c) Band structure along the dash line in (b).

Flat bands are highlighted in red. (d) Atomic coordinates of the twisted bilayer system in real space with the arrows indicating the directions of wave packet propagation.

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Invited Graphene Materials, Devices and Integration: Challenges and Opportunities

Luigi Colombo

colombo@ti.com

Texas Instruments, Dallas, TX 75243 USA

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surface roughness than metals, just to name a few.

Dielectrics having a range of dielectric constants, bandgap and band offsets may be necessary depending upon the device structure. The metal contact resistance problem is still to be solved although progress is being made. The objective of this presentation is to review the status of graphene growth, and its integration with dielectrics and metal contacts, and present the status and challenges of fabricating the various proposed devices.

[1] International Technology Roadmap for Semiconductors. http://www.itrs.net/Links/2011ITRS/Home201 1.htm, 2011, p.^pp. Pages.

[2] G. Fiori, A. Betti, S. Bruzzone, and G. Iannaccone, "Lateral Graphene-hBCN Heterostructures as a Platform for Fully TwoDimensional Transistors," ACS Nano, vol. 6, pp.

2642-2648, Mar 2012.

[3] Q. Zhang, T. Fang, H. L. Xing, A. Seabaugh, and D. Jena, "Graphene Nanoribbon Tunnel Transistors," IEEE Electron Device Letters, vol.

29, pp. 1344-1346, Dec 2008.

[4] A. C. Seabaugh and Q. Zhang, "Low-Voltage Tunnel Transistors for Beyond CMOS Logic," Proceedings of the IEEE, vol. 98, pp. 20952110, Dec 2010.

[5] S. K. Banerjee, L. F. Register, E. Tutuc, D. Reddy, and A. H. MacDonald, "Bilayer PseudoSpin Field-Effect Transistor (BiSFET): A Proposed New Logic Device," IEEE Electron Device Letters, vol. 30, pp. 158-160, Feb 2009.

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References

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There has been significant progress in graphene research since its isolation. The future of graphene for the electronics industry will depend on our ability to grow it or form it from graphite sources with the desired characteristics that meet the requirements of the specific application. The semiconductor industry is still pursuing devices that meet beyond complementary metal oxide semiconductor (CMOS) device requirements. The current transistor approaches that use FinFET, IIIVs compounds or SiGe for channel materials are expected to meet the device requirements that will bring the transistor to the CMOS limit.[1] In order to meet the beyond CMOS device requirements, such as low voltage, <<1V, operation and continue on the current Mooreâ&#x20AC;&#x2122;s law trends, it will be necessary to introduce devices that will be based perhaps on new physics.

Graphene-based devices are being explored to meet these requirements and are being studied by many groups, but none of the devices have been demonstrated to meet the requirements yet.

Some of the devices studied are (1) graphene tunnel field effect transistor (TFET) [2-4], (2) bilayer pseudospin FET (BisFET)[5], (3) Veselago lens based device [6, 7], and most recently (4) the lateral tunnel FET (LTFET) [8, 9]. However, there are many materials and integration challenges for any of these approaches that are being addressed in order to fabricate of them. But there are still many challenges. For example it is likely that single crystal or very large single crystal graphene will be needed in order to decrease the effects grain boundaries but more importantly it will be necessary to grow films on substrates that have a much lower thermal coefficient of expansion difference with respect to graphene in order to minimize wrinkles, and substrates that lower

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[6] S. Chun-Yung and L. Ji Ung, "The ultimate switch," Spectrum, IEEE, vol. 49, pp. 32-59, 2012.

[7] V. V. Cheianov, V. Fal'ko, and B. L. Altshuler, "The focusing of electron flow and a Veselago lens in graphene p-n junctions," Science, vol.

315, pp. 1252-1255, Mar 2007.

[8] G. Fiori and G. Iannaccone, "Ultralow-Voltage Bilayer Graphene Tunnel FET," IEEE Electron Device Letters, vol. 30, pp. 1096-1098, Oct 2009.

[9] M. P. Levendorf, C. J. Kim, L. Brown, P. Y. Huang, R. W. Havener, D. A. Muller, and J. Park, "Graphene and boron nitride lateral heterostructures for atomically thin circuitry," Nature, vol. 488, pp. 627-632, Aug 2012.

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Oral

The unique properties found in graphene-based material are paving the way to the development of a new generation of multifunctional flexible electronic applications such as flexible communication devices, sensors, photovoltaics, etc.. Understanding the optoelectronic properties of graphene based heterostructures is the first step for exploiting the full potential of this carbon material in flexible and transparent photovoltaic devices. Here we pioneer the field of all graphene photodectors based on heterostructures consisting of the recently discovered FeCl3 intercalated fewlayer graphene (FeCl3-FLG, dubbed graphexeter) and pristine graphene. The FeCl3 intercalation is known to dope graphene to record high charge carrier densities (up to 9*10^14 cmâ&#x2C6;&#x2019;2) and it drops the room temperature square resistance of graphene to just a few Ohms making this material the best transparent conductor. At the FeCl3-FLG/graphene interface we observe a dominant photovoltage comparable to the signal measured at the graphene/Au interface. We observe a sign reversal of the photovoltage upon sweeping the chemical potential of the pristine FLG through the charge neutrality point and we show that this is due to the photothermoelectric effect. Our results demonstrate that FeCl3-FLG can replace expensive and opaque metals in photovoltaic architectures rendering them mechanically flexible and transparent.

The unprecedented combination of the recently discovered FeCl3-FLG embedded with graphene in heterostructures for photovoltaics constitute a step forward to all-graphene-electronics

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m.f.craciun@exeter.ac.uk

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Centre for Graphene Science, University of Exeter, Exeter (UK)

Monica F. Craciun F. Withers T. H. Bointon and S. Russo

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All graphene photodetectors

Keynote Carbon Nanotubes and Graphene Nanoribbons

Hongjie Dai

hdai1@stanford.edu J.G. Jackson- C.J. Wood Professor of Chemistry. Department of Chemistry Stanford University Keck Science Building, Rm 125 380 Roth Way Stanford, CA 94305

66

This talk will present our work on carbon nanotubes, graphene nanoribbons and grapheneinorganic hybrid nanomaterials. First, biological applications of carbon nanotubes will be discussed including a new fluorescence imaging method in the so called NIR-II region in the spectral window of 1000-1400nm. NIR fluorescence enhancement of carbon nanotubes and organic fluorophores will be presented on a novel plasmonic substrate for 3D molecular tracking and biological detection. I will then talk about graphene nanoribbons, including several methods recently developed in our lab to form high quality graphene nanoribbons with narrow widths and smooth edges. Lastly, I will talk about our recent work on making inorganic nanoparticles and nanocrystals on graphene sheets and carbon nanotubes for energy storage and electrocatalytic applications.

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Oral

Terahertz Center, University of Regensburg, 93040 Regensburg, Germany A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg, Russia 3 Department of Physics, Chemistry and Biology, Linköping University, S-58183 Linköping, Sweden 4 Chalmers University of Technology, S-41296 Göteborg, Sweden 5 The Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, Texas 77005, U.S.A. 2

Introduction We report on the experimental and theoretical study of magnetic quantum ratchet effects in graphene. It is shown that single-layer graphene samples subjected to an in-plane magnetic field rectify ac electric current converting it into a dc electric signal. The dc response is observed for both linearly polarized and circularly polarized ac electric field of terahertz (THz) radiation. We show that the ratchet current in graphene is sensitive to the radiation polarization and, for circular polarization, contains a helicitydependent component. We present a microscopic theory of the effect and show that the current stems from the asymmetry of electron transport which is caused by the mixing of π- and σ-band states in the magnetic field and structure inversion asymmetry of graphene samples. The dc current changes a sign by switching the magnetic field polarity and proportional to the square of the amplitude of the ac electric field, thus, representing the magnetic quantum ratchet effect.

Samples and setup The experiments were carried out on single-layer graphene samples either grown on the Siterminated face of a 4H-SiC(0001) semi-insulating substrate or synthesized by chemical vapor deposition on Si/SiO2. For optical experiments squared shaped samples (5 x 5 mm²) with ohmic contacts were prepared. Hall measurements reveal electron concentrations of the order of (3-7) x 1012 cm-2, Fermi energies ranging from 200 to 300 meV, and mobility of about 1000-2000 cm²/Vs. The samples were laced into an optical cryostat with zcut crystal quartz windows and split-coil superconducting magnet. All experiments were performed applying normal incidence of THz radiation and in-plane magnetic fields between B = -7 T and B = +7 T, see inset in Fig. 1. Terahertz

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1

S. A. Tarasenko2, P. Olbrich1 J. Karch1, M. Hirmer1 F. Müller1, M. Gmitra1 J. Fabian1, R. Yakimova3 S. Lara-Avila4, S. Kubatkin4 M. Wang5, R. Vajtai5 P. M. Ajayan5, J. Kono5 and S. D. Ganichev1

christoph.drexler@physik.uniregensburg.de

radiation was generated by a high power pulsed NH3 laser operating at frequencies f = 3.3 THz, 2 THz or 1.1 THz with peak powers P up to 10 kW within 100 ns. The polarization of the radiation was varied utilizing λ/2 and λ/4 x-cut quartz plates of proper thickness. The sample temperature was varied from 4.2 up to 300 K. The current generated

by THz radiation in the unbiased graphene layer was measured via the voltage drop across a 50 Ohm load resistor. The voltage was measured with a storage oscilloscope. The measured current pulses of 100 ns duration reflect the corresponding laser pulses.

Results and microscopic theory The excitation of graphene samples by ac electric field of THz radiation results in a photocurrent which scales linearly with the radiation intensity and the magnetic field B [1]. The current is observed in a wide range of frequencies and temperatures. Figure (1) shows the behavior of the signal under variation of the temperature T yielding that at low T it is constant whereas it decreases with the increase in T at higher temperatures. For linearly polarization radiation, the current depends on the angle between the polarization plane and the static magnetic field.

For circular polarization, the current reveals both polarization-independent and helicity-sensitive components. All these observations are in agreement with the developed microscopic model, see Fig. 2, and theory of the magnetic quantum ratchet effect in graphene. The theory considers non-linear high-frequency transport of Dirac fermions in graphene in the presence of asymmetric scattering induced by static magnetic field. It demonstrates that the current emerges if the spatial symmetry of graphene layers is broken by the environment, e.g., the substrate or adatoms on the graphene surface. Thus, the magnetic

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1

Christoph Drexler

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Terahertz-radiation-induced magnetic quantum ratchet effect in graphene

quantum ratchet effect can serve as a direct and non-invasive measure of structure inversion asymmetry in graphene.

References [1] C. Drexler, S.A. Tarasenko, P. Olbrich, J. Karch, M. Hirmer, F. M端ller, M. Gmitra, J. Fabian, R. Yakimova, S. Lara-Avila, S. Kubatkin, M. Wang, R. Vajtai, P. M. Ajayan, J. Kono, and S.D. Ganichev, Nature Nanotechnology 8, 104 (2013).

Figures

Figure 1: Experimental overview of the ratchet current in graphene. Temperature dependence of the ratchet current jx for the in-plane magnetic field By. Left inset shows the linear dependence of the current on the magnetic field for different samples. Right inset shows the experimental geometry.

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Figure 2: Microscopic model. The ratchet-and-pawl mechanism is realized due to the static magnetic field B and the spatial asymmetry of graphene induced by the hydrogen adatoms (blue spheres). The resulting spatial distribution of the electron density is shown by the red colour scheme. If electrons, at any time, are driven to the right, their orbitals are shifted upwards due to a quantum analogue of the Lorentz force (left panel). Consequently, their mobility decreases. A half a period later, when electrons flow left, their orbitals are shifted down resulting in an increased mobility (right panel). The imbalance in mobility for left- and rightmoving electrons results in a net dc electric current.

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Invited Photoluminescence in twodimensional crystals

3

Department of Physics, National University of Singapore, Singapore 117542 Department of Chemistry, National University of Singapore, Singapore 117543 Graphene Research Centre, National University of Singapore, Singapore 117546

Two-dimensional (2D) crystals derived from layered structures exhibit a unique set of properties as elegantly demonstrated for graphene. Semiconducting 2D structures such as MoS2 sheets are attractive building blocks for novel electronic and optoelectronic devices. In this talk, I will report photoluminescence properties of group 6 transition metal dichalcogenide (TMD) 2D crystals and discuss how their spectral features provide insight into the evolution of chemical, structural, and electronic properties of these materials.

A single layer MoS2 is a direct gap semiconductor in striking contrast to its indirect gap bulk counterpart [2]. As a result, single layer MoS2 exhibits distinct band gap photoluminescence. We find that photoluminescence spectra of mono- to few-layer WS2 and WSe2 indicate that their band structure undergoes a similar indirect-to-direct gap transition when thinned to a single monolayer (Fig. 1) [3]. The transition is evidenced by distinctly enhanced PL peak centered at 630 and 750 nm in monolayer WS2 and WSe2, respectively. We demonstrate that indirect gap emission and direct gap hot electron emission is pronounced in fewlayer WSe2 due to small energy difference between the two transitions. At sufficiently high temperatures, short-range interlayer interactions in multilayer sheets weaken such that each layer behaves like an individual monolayer, giving rise to enhanced photoluminescence similar to the case of MoSe2 [4].

References [1] Wang et al. Nat. Nanotechnol. 7, 699 (2012).

[2] K. F. Mak et al. Phys. Rev. Lett. 105, 136805 (2010).

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[3] Zhao et al. ACS nano. 7, 791 (2013).

[4] Tongay et al. Nano Lett. 12, 5576 (2012).

Figures

Figure 1: Photoluminescence spectra of 1 to 5 layer WS2 (left) and WSe2 (right).

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2

1,2,3

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1

Goki Eda

Invited 1

Determining Volume of 2D nanomaterials and Hydrogenated Reconstructed Klein edges

Chris Ewels 1 P. Wagner 1 B. Humbert V. Ivanovskaya1,2 1 J. - J. Adjizian and 1,3 P. Briddon

1

chris.ewels@cnrs-imn.fr philipp.wagner@cnrs-imn.fr

Institute of Materials (IMN), CNRS, Université de Nantes, BP32229, Nantes, France 2 Thales-CNRS, 1 Av. A.Fresnel, 91767 Palaiseau & Université Paris-Sud, 91405 Orsay, France 3 University of Newcastle, Newcastle upon Tyne, NE1 7RU, United Kingdom

Materials mechanical constants such as Young’s Modulus, Poisson’s ratio or bulk modulus rely on knowledge of applied force and the precise dimensions of a material. However the concept of cross-sectional area (e.g. wall thickness of CNTs) and volume (e.g. graphene sheet) become difficult to define as material size decreases towards the atomic scale. In the current study we propose to define material volume based on an isosurface of the electron density, such that the average nano-object electron density matches that of a related parent bulk system [1]. This new approach is universal, valid for a wide range of different geometries (tubes, sheets, …), and accurately reproduces previous geometry specific studies [2]. It also leads to surprising new physics.

While Young’s Modulus is often considered purely a function of bond strength we demonstrate with this approach the importance of changing volume. As an example we show that shifting the Fermi level directly modifies the graphene mechanical constants, showing doping-tunable mechanical response.

Via density functional calculations we show that the zigzag edge is not the most stable

References [1] Ph. Wagner, V. V. Ivanovskaya, M. J.Rayson, P. R. Briddon, C. P. Ewels, J. Phys.

Cond. Matt., in press (2013).

[2] J. P. u, “Elastic Properties of Carbon Nanotubes and Nanoropes“, Phys. Rev. Lett., 79, (1997) 1297.

[3] V. V. Ivanovskaya, A. Zobelli, Ph. Wagner, M. Heggie, P. R. Briddon, M. J. Rayson, C. P. Ewels, Phys. Rev. Lett., 107 (2011) 065502.

[4] Ph. Wagner, PhD Thesis, Université de Nantes, April 2013 (interested in any postdoc positions!).

[5] Ph. Wagner, V. V. Ivanovskaya, J. J. Adjizian, P. R. Briddon, B. Humbert, C. P. Ewels, submitted (2013).

[6] T. Wassmann, A. P. Seitsonen, A. M. Saitta, M. Lazzeri, F. Mauri, Phys. Rev. Lett., 101 (2008) 096402.

[7] Ph. Wagner, C. P. Ewels, V. V. Ivanovskaya, P. R. Briddon, A. Pateau, B. Humbert Phys.

Rev. B, 84 (2011) 134110.

[8] Full references can be found at www.ewels.info or via email at chris.ewels@cnrs-imn.fr.

_ _

hydrogenated edge in the <2 1 1 0> orientation.

Instead a parallel cut results in a Klein edge structure (Figure 1), which when reconstructed [3] and hydrogenated is significantly more stable than the zigzag (Figure 2). The resultant structure, and its associated structural variants, have stabilities approaching that of the armchair edge [4,5].

Figures

70

Figure 1: Nanotube splitting to give either zigzag or reconstructed Klein edges [2,3]. A hydrogenated reconstructed Klein nanoribbon is more stable by at least 0.027 eV/Å.

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Invited Atomically Precise Synthesis of Graphenes: A Bottom-up Approach

Xinliang Feng

feng@mpip-mainz.mpg.de Max Planck Institute for Polymer Research, Mainz, Germany

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References

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[1] Feng, X.; Marcon, V.; Pisula, W.; Hansen, M. R.; Kirkpatrick, J.; Grozema, F.; Andrienko, D.; Kremer, K.; Müllen, K. Nature. Mater. 2009, 8, 421-426.

[2] Cai, J.; Ruffieux, P.; Jaafar, R.; Bieri, M.; Braun, T.; Blankenburg, S. ; Muoth, M.; Seitsonen, A. P.; Saleh, M.; Feng, X. L.; Müllen, K.; Fasel, R. Nature. 2010, 466, 470-473.

[3] Pang, S. P.; Hernandez, Y.; Feng, X. L.; Müllen, K. Adv. Mater. 2011, 23, 2779-2795.

[4] Pisula, W.; Feng, X. L.; Müllen, K. Chem. Mater.

2011, 23, 554-567.

[5] Dossel, L.; Gherghel, K.; Feng, X. L.; Müllen, K. Angew. Chem. Int. Ed. 2011, 50, 2540-2543.

[6] Chen, L.; Hernandez, Y.; Feng, X. L.; Müllen, K. Angew. Chem. Int. Ed. 2012, 51, 7640-7654.

[7] Schwab, M. G.; Narita, A.; Hernandez, Y.; Feng, X. L.; Müllen, K. J. Am. Chem. Soc. 2012, 134, 18169-18172.

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Graphene, a two-dimensional carbon allotrope, has demonstrated exceptional physical properties such as ultrahigh charge carrier mobility, quantum Hall effect, and good optical transparency, which make it a realistic candidate for a number of electronic applications. The future research and application of graphene urgently calls for efficient synthesis at different size and length scales with high chemical definition.

Top-down production of graphene relies on peeling-off graphene layers from graphite in solution or on substrate. The high-quality graphene sheets can be also prepared by chemical vapor deposition. To open up the band gap of graphenes, a lateral confinement must be introduced, such as to cut graphene sheet into thin strips or unzipping carbon nanotubes into nanoribbons. In this presentation, we will demonstrate a bottom-up synthetic route to nanographenes and graphene nanoribbons, which provides an atomic precise synthesis of graphenes with robust nanostructures. This synthetic strategy is based upon the cyclodehydrogenation (“graphiti ation”) of well-defined dendritic (3D) polyphenylene precursors with different topologies. The advantage of this approach is obvious as the size, shape and edge control, structural perfection and processability (solution, melt, even gas phase) of graphenes can be attained. Wide applications in electronic devices are possible with using nanographenes and graphene nanoribbons when they are rationally processed on the surfaces.

Oral Electronic properties of MoS2-WS2 bilayers

Joaquin Fernández-Rossier K. Kosmider and J. W. González

International Iberian Nanotechnology Laboratory (INL), Braga, Portugal

joaquin.fernandez-rossier@inl.int

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The fabrication of electronic devices based on a single or a few layers of transition metal dichalcogenides, such as MoS2 and WS2, holds the promise of expanding the graphene revolution into an exciting new arena. Unlike graphene, the MoS2 and WS2 monolayers have a direct band gap in the 1.8eV range and, due to the strong spin orbit coupling (SOC) and the specifics of their atomic structure, they present strong spin-valley coupling.

This has been demonstrated by means of optical pumping experiments which to valley polarized exciton population [1-3].

Here we study the electronic structure of a heterojunction made of two monolayers of MoS2 and WS2. Our first-principles density functional calculations show that [4], unlike in the homogeneous bilayers, the heterojunction has an optically active band-gap, smaller than the ones of MoS2 and WS2 single layers. We find that that the optically active states of the maximum valence and minimum conduction bands are localized on opposite monolayers, and thus the lowest energy electron-holes pairs are spatially separated. Our findings portrait the MoS2-WS2 bilayer as a prototypical example for band-gap engineering of atomically thin two-dimensional semiconducting heterostructures.

We also find that, contrary to previous theory work, there is spin splitting at the K point both in the valence and the conduction band. We discuss the physical origin of the splitting at the conduction band and derive an effective Hamiltonian making use of Wannier functions and perturbation theory.

References [1] H. Zeng, J. Dai, W. Yao, D. Xiao, and X. Cui, Nature Nanotechnology 7, (2012) 490.

[2] K.F Mak, K. He, J. Shan, and T.F. Heinz, Nature Nanotechnology 7, (2012) 494.

[3] T. Cao, G. Wang, W. Han, H. Ye, C. Zhu, J. Shi, Q. Niu, P. Tan, E. Wang, B. Liu, and J. Feng, Nature Communications 3, (2012) 887.

[4] K. Kosmider, J. Fernández-Rossier, arXiv:1212.0111.

Figures

Figure 1: Caption: Calculated electronic structure of MoS2, WS2 monolayers and bilayers, as well as the (Mo-W)S2 bilayer.

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Keynote Raman Spectroscopy in Graphene and Layered Materials

Andrea C. Ferrari

Cambridge Graphene Centre, Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 OFA, UK

[1] A. C. Ferrari et al. Phys. Rev. Lett 97, 187401 (2006).

[2] A. C. Ferrari et al. Solid State Comm. 143, 47 (2007).

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GRAPHENE 2013

References

[3] A. C. Ferrari, D. M. Basko Nature Nanotech. 8, 235 (2013).

[4] D. M. Basko, New J. Phys. 11, 095011 (2009).

[5] M. Kalbac et al. ACS Nano 10, 6055 (2010).

[6] C. F. Chen et al. Nature 471, 617 (2011).

[7] P. H. Tan et al. Nature Materials 11, 294 (2012).

[8] J. N. Coleman, et al. Science 331, 568 (2011).

[9] F. Bonaccorso et al. Materials Today 15, 564 (2012).

[10] X. Zhang et al. Phys. Rev. B 87, 115413 (2013).

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Raman spectroscopy is an integral part of graphene research [1-3]. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups.

This, in turn, provides insight into all sp2-bonded carbon allotropes, because graphene is their fundamental building block. I will review the state of the art, future directions and open questions in Raman spectroscopy of graphene. The essential physical processes will be described, in particular those only recently been recognized, such as the various types of resonance at play, and the role of quantum interference [3-6]. I will update all basic concepts and notations, and propose a terminology that is able to describe any result in literature [3]. Few layer graphene (FLG) with less than 10 layers do each show a distinctive band structure. There is thus an increasing interest in the physics and applications of FLG. I will discuss the interlayer shear mode of FLG, and show that the corresponding Raman peak, named C, measures the interlayer coupling [7]. A variety of layered materials can also be exfoliated to produce a whole range of two dimensional crystals [8,9].

Similar shear and layer breathing modes are present in all these materials, and their detection provides a direct probe of interlayer interactions. A simple chain model can be used to explain the results, with general applicability to any layered material [10]

Oral Spin-polarized currents in energygapped graphene induced by strainenhanced spin-orbit interaction

Mauro S. Ferreira1 2 A. T. Costa and 3 A. H. Castro Neto

1

School of Physics and CRANN, Trinity College Dublin, Dublin 2, Ireland Instituto de Fisica, Universidade Federal Fluminense, Niteroi, RJ, Brazil 3 Graphene Research Centre, National University of Singapore 2

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While graphene is unquestionably a material with impressive technological achievements, the goals of opening a bandgap in its electronic structure and of having control over the spin of its charge carriers remain elusive. Here, we demonstrate that enhancement of the spin-orbit interaction and an externally applied magnetic field are the required ingredients to achieve both such goals simultaneously, i.e., to introduce a spin dependence in the transport properties of graphene as well as induce an energy gap in its band-structure. We suggest two possible manners in which the effect can be achieved, namely through spin-orbit-interaction-enhancing impurities adsorbed onto sizable areas of a graphene sheet or through strain engineering the graphene sheet in a superlattice structure.

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Oral Graphene RF Design: what really matters

Gianluca Fiori G. Iannaccone

gfiori@mercurio.iet.unipi.it

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application, and show that they represent significant improvement with respect to monolayer graphene FETs. To this purpose we extensively exploit the open source device simulator NanoTCAD ViDES [5], based on the selfconsistent solution of the three-dimensional Poisson equation and of the Schroedinger equation with an atomistic tight-binding Hamiltonian, within the non-equilibrium Green’s functions formalism (NEGF).

The simulated structure is the one considered in the experiments by Wu et al. [1] and shown in Fig. 1, where the top oxide has been reduced to 4 nm.

To isolate and understand the improvements due to bilayer graphene, we show in Fig. 2 the comparison between the output characteristics of two identical devices, biased with a back-gate voltage VBG = 50 V, where the only difference is the use of monolayer graphene (left) or bilayer graphene (right) as channel. One can see the much improved current saturation and transconductance provided by bilayer graphene, even with a small bandgap (0.22 eV).

As shown in Fig. 3, the backgate voltage is key to tune the energy band gap, and the main factor responsible for the high intrinsic gain achievable with bilayer graphene. The larger the VBG, the larger the bandgap, and in turn the larger the intrinsic gain. In Fig. 4 instead we show the achievable fT and fMAX, including some nonidealities such as stray capacitances, and a varying contact resistance RS. For the bilayer graphene device, for RS = 0 Ω, we obtain fT 1.5 THz and fMAX 2 ÷ 4 THz. This is very promising with respect to monolayer graphene devices, where the low output resistance pushes fMAX below fT. If a finite contact resistance is considered both fT and fMAX decrease, but for RS = 80 μm, as required by ITRS [6], we have both in the THz range.

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It is a widely held opinion in the graphene community that radiofrequency (RF) applications are the most promising when trying to exploit graphene as device channel material, since they can harness graphene properties such as ultrahigh mobility and large saturation velocity, without suffering from the lack of a band gap [1], [2].

The main figure of merit considered so far in order to assess graphene performance for RF applications is the cut-off frequency fT, i.e. the frequency at which the short-circuit current gain is unity. In particular, in the recent years we have been the witnesses of a kind of “gold-rush”, where larger and larger fT have been obtained at a rapid pace, reaching few hundred GHz [3].

However, the main relevant parameter in RF graphene electronics is not fT, but rather fMAX, i.e. the maximum frequency at which one can obtain power gain. Unfortunately, fMAX has often been neglected, while investigating graphene RF performance, and it must be put at the center of the scene.

The absence of band gap in graphene can indeed have a negative impact in graphene short channel devices, where transport is quasi ballistic and drift velocity saturation cannot occur, interband tunneling suppresses the output differential resistance r0, the intrinsic voltage gain Av, and therefore fMAX. Recently, Szafranek et al. [4] have shown with experiments and simulation that a larger r0 and Av can be obtained by using bilayer graphene. The reason is that by applying an electric field perpendicular to the bilayer graphene plane it is possible to induce a gap of 100-200 meV. Even such a small gap, is sufficient to significantly improve saturation of the device output characteristics.

Here we investigate with atomistic simulations graphene bilayer FETs for radio frequency

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Dipartimento Ingegneria dell’Informa ione, Universita’ di Pisa, Via Caruso 16, 56126 Pisa, Italy

To conclude, bilayer graphene devices with ideal contact resistances are promising with respect to single layer graphene device. The main single performance booster is the use of bilayer graphene channel, which has a band gap of up to 220 meV, sufficient to suppress interband tunneling and provide acceptable output resistance.

References [1] Y. Wu et al., Nature, 472 (2011) 74.

[2] G. Iannaccone et al., IEDM Tech. Dig., 1 (2009) 10.4.1.

[3] L. Liao et al., Nature, 467 (2010), 305.

[4] B.N. Szafranek et al., Nano Lett., 12 (2012), 1324.

[5] All documentation on NanoTCAD ViDES can be found at url: http://vides.nanotcad.com.

[6] ITRS Roadmap, available at http://public.itrs.net.

Figure 3: Left: energy gap as a function of the backgate voltage for different VGS; Right: intrinsic gain Av as a function of Egap for different VGS.

Figures Figure 4: fT and fMAX as a function of IDS for VGB= 50 V and different contact resistances.

Figure 1: Device structure of Ref. [1] and simulated domain.

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Figure 2: Output characteristics with VBG = 50 V with monolayer graphene channel (left) and bilayer graphene channel (right).

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Oral Graphene Enhanced Electrode Performance for Li-ion Batteries

Rahul Fotedar

rf@graphenebatteries.no

Graphene Batteries, Forskningsveien 1, 0314 Oslo, Norway

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significantly enhance the power of a battery and bridge the gap between high energy and high power cells currently offered in the market. Finally the materials will offer exceptional thermal properties which will increase the safety and life time of the battery translating into increased longevity and reduced depreciation costs of the battery.

The capacity in a battery cell depends on the amount of electrode material. A method to achieve a high capacity is to use a thick layer of electrode material. However this requires that the electrical conductivity of the electrode material is high.

LFP/Graphene composites as shown in the Figure 1 below provide both higher gravimetric and volumetric energy density than normal LFPelectrodes with same formulation. Extensive work is under way to reduce the graphene content in the electrodes such that the columbic efficiency and ultimately the cycle life of the cell is highly improved.

Applications targeted are batteries for EV, ships and smart grid.

[1] Wendelbo, R. and Fotedar, S. Norw. Patent application No. 20120917.

[2] Wendelbo, R. and Fotedar, S. Norw. Patent application No. 20121111.

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References

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Li-ion batteries are the largest and fastest growing segment amongst the various battery technologies. They provide the highest energy density per unit weight and volume and is the only technology which offers a realistic solution for development of electric and hybrid vehicles.

However there are still some major limitations which are preventing the mass scale production and adoption of electric vehicles. The battery pack in a car presently costs about 30% of the total car which makes the cars expensive. The maximum driving range of a car needs to go up significantly for it to be seriously considered for most customers. Last but not the least the safety issues of putting a huge high energy battery also needs to be sufficiently tackled. Hence the requirement for developing safer, lighter and cheaper batteries is driving enormous development in the field of Liion batteries.

Graphene Batteries focuses on improving existing and future candidate cathode and anode materials with the unique properties of graphene [1].

Graphene has exceptional electronic and thermal conductivity which will impart fundamental changes to the performance of the battery. GB has already made a prototype material in lab-scale which show 20 times higher conductivity than a "state-of-the-art" industrial material, with the same carbon-content, by using in-house prepared GO (Figure 2) subsequently thermally reduced to the graphene derivative RGO. By introducing graphene combined with special formulation techniques [2], we have calculated that our material can reduce the total cost of the battery by 30 â&#x20AC;&#x201C; 40 %. An important part of the savings are related to reduction in the amount of additional materials needed, such as separators and conductive diluents in a Li-ion cell. It will

Figures

Figure 1: LFP with 2 % delaminated RGO.

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Figure 2: Original graphene oxide.

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Oral Exploring new ways of chemical vapor deposition technology to produce graphene

Grup FEMAN, Departament de Física Aplicada I Òptica, IN2UB, Universitat de Barcelona, Martí i Franquès 1, 08028, Barcelona, Spain

Victor-Manuel Freire S. Chaitoglou A. Ramírez M. Reza Sanaee E. Pascual J.-L. Andújar and E. Bertran. victor.freire@ub.edu

Chemical vapor deposition (CVD) is a very popular technology to produce monolayer graphene.

However, this technology is associated with relatively high temperatures and supersaturation carbon precursor conditions to produce a graphene monolayer. The goal of this work is to explore different ways of growing graphene on copper over silicon by means of thermally activated chemical vapor deposition using a low precursor pressure. Growing processes were performed in a reactor with a quartz tube oven at high vacuum conditions. The activated copper substrate was exposed to methane gas at a low pressure and annealed below 1000 C. Results indicate a possible solution of Cu on a Ni barrier (grown in order to avoid diffusion of Cu into c-Si) forming a polycrystalline surface Cu/Ni thin layer, which favors the nucleation of graphene. During the annealing Ni/Cu drops are formed clearing large areas of silicon substrate (104 µm2, Fig. 1).

The characterization by Raman spectroscopy, XRay spectroscopy (EDS) and scanning electron microscopy (SEM) evidenced that large-areas of crystalline silicon appeared 99% copper free and coated by graphene. The Raman analysis of these areas assessed the only presence of graphene of one-two layers by showing the characteristic 2D band and the ratio 2D/G ≥ 1 (Fig. 2). The direct growth of graphene on silicon wafers without transferring facilitates the application of lithographic processes and the possibility to produce graphene-based electronic devices.

[2] J. Sun et al., IEEE Transactions on Nanotechnology, 11 (2012) 255.

[3] X. Li et al., Science, 324 (2009) 1312.

[4] C. A. Howsare et al., Nanotechnology, 23 (2012) 135601.

[5] Z. Ni et al., Nano. Res., 1 (2008) 273.

[6] V.-M. Freire et al., Jpn. J. Appl. Phys., 52 (2013) 01AK02.

References

Figure 2: Raman spectra of monolayer and bilayer graphene. Ratio between 2D/G peaks are much bigger than 1 in most of monolayers.

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Figure 1: Raman mapping of areas about 104 µm2. The surface is covered with 80% monolayer graphene and 20% of bilayer graphene.

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[1] K.S. Novoselov et al., Science, 306 (2004) 666.

Figures

Oral 1

CVD graphene and graphene for sensing application

Wangyang Fu 1 1 C. Nef , A. Tarasov 1 1 M. Wipf , R. Stoop O. Knopfmacher2, M. Weiss1 1 M. Calame and 1 C. Schönenberger

1

Department of Physics, Basel University, 4054-Basel, Switzerland Department of Chemical Engineering, Stanford University, Stanford, 94305-California, United States 2

wangyang.fu@unibas.ch christian.schoenenberger@unibas.ch

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functionalization of graphene has to be introduced [4].

References [1] K. S. Novoselov, et al, “Field Effect in Atomically Thin Carbon Films”, Science, 306 (2004) 666.

[2] X. S. i, et al, “ arge-Area Synthesis of HighQuality and Uniform Graphene Films on Copper Foils”, Science, 324 (2009) 1312.

[3] W. Y. Fu, et al, “Graphene Transistors Are Insensitive to pH Changes in Solution”, Nano Lett., 11 (2011) 3597.

[4] W. Y. Fu, et al, “High Mobility Graphene IonSensitive Field-Effect Transistors by Noncovalent Functionali ation”, to be submitted.

Figures (a)

(b) 350

Vref Electrolyte solution

Pt

Isd

VPt

pH 7 pH 7B fitting

Gsd (S)

Owing to its novel electrical properties [1] and large surface to volume ratio, graphene is regarded as excellent candidate for ultrasensitive biological (chemical) detection and diagnosis devices. Before reaching such ambitious biological applications of graphene, its response to various electrolyte compositions, where the biomolecules site in, has to be clarified first of all. In fact, large variations in sensitivities have been reported for graphenebased ion sensors. For example, contradicted pH sensitivities ranging from a low value of 12mV/pH to a supra-Nernst value of 99mV/pH (Nernst value, 60mV/pH at room temperature), were reported in previous literature.

The present work [1] serves to resolve this discrepancy. We start with either exfoliated graphene or chemical vapor deposition (CVD) graphene [2] grown on 25 um thick copper foils.

The CVD graphene allows for the transfer of highquality graphene with lateral scale of many centimeters on arbitrary substrates. Further characterizations indicate that we achieved predominant uniform, monolayer graphene with high mobility ~3000cm2/Vs. As shown in Fig. 1, liquid-gated graphene field-effect transistors (GFETs) with reliable performance are developed.

It is revealed that ideal defect-free graphene should be inert to electrolyte composition changes in solution, whereas a defective one responses to electrolyte composition. This suggests that graphene cannot sense the chemical potential of protons or ions (the proton or KCl concentration), but rather senses the electrostatic potential of the solution [3]. This finding sheds light on the large variety of pH or ion-induced gate shifts that have been published for GFETs in the recent literature.

As a next step to target graphene-based (bio-) chemical sensing platform, non-covalent

300

Vsd SiO2/Si

Vdirac

250 Epoxy Photoresist

Au/Ti Graphene

0.2

0.4 0.6 Vref (V)

Figure 1: (a) Schematics of the experimental setup and the electrical circuitry of the liquid-gated GFET. The gate voltage VPt was applied to the solution via a Pt wire. The electrostatic potential in solution Vref was monitored by the reference calomel electrode. (b) Two data sets obtained for pH = 7 are shown to illustrate the excellent degree of reproducibility. Here a bipolar transfer curve is observed corresponding to different type of charge carriers that can continuously be tuned from holes (left) to electrons (right) with the charge-neutral point VCNP at minimum Gsd.

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Invited Graphene nanopore platform for single-molecule studies

Slaven Garaj

slaven@nus.edu.sg

References [1] Garaj, S. et al. Nature 467 (2010) 190â&#x20AC;&#x201C;193.

[2] Garaj, S., Liu, S., Branton, D. & Golovchenko, J. A. arXiv:12044361 (2012)ess.

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Graphene employed in many research fields often showed unmatched, or distinctively unique properties within the given field. We demonstrate that graphene-based nanopore sensors have potential resolution and sensitivity to nondestructively read out individual nucleobases along the long DNA molecule [1] â&#x20AC;&#x201C; which is the paramount challenge in the field of physical DNA and protein sequencing.

In a nanopore device, individual DNA molecule in aqueous salt solution is threaded through a nanometer-scaled pore in a linear fashion, allowing for sequential parts of the molecule to be localized and interrogated within the pore. The properties of the localized part of the molecule can be deduced by measuring ionic current modulation through the obstructed nanopore, or by monitoring current in a nanopore-integrated electrical sensor. We show that single-layer graphene membrane has sub-nanometer effective thickness in water, lending to graphene nanopores sub-nanometer resolution along the length of a DNA molecules [1]. Furthermore, we demonstrate that graphene nanopores have ultrahigh sensitivity on diameter variations of the threading molecule, which is the direct consequence of grapheneâ&#x20AC;&#x2122;s monoatomic thickness [2]. Finally, we discuss the physical properties of graphene nanopores, their interaction with the DNA molecules, and implications of our results on the prospects for next-gen DNA sequencing.

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Graphene Research Center, National University of Singapore, Singapore Dept. of Physics and Dept. of Bioengineering, National University of Singapore, Singapore

Oral Bostjan Genorio 2 W. Lu 2 J. M. Tour

1

bostjan.genorio@ki.si

Centre of Excellence for Low-Carbon Technologies, Hajdrihova 19, 1000 Ljubljana, Slovenia 2 Department of Chemistry, Rice University, 6100 Main Street, Houston, Texas 77005, United States

Graphene Nanoribbons (GNRs) are promising material with a high aspect ratio, possessing interesting mechanical and electrical properties.

Thus it is a potential building block for numerous applications. However, two major issues need to be solved before full advantage of GNRs is to be taken: a) bulk preparation of well-defined GNRs and b) processability.

Various preparation techniques of GNRs have been reported by several groups, but processability still remains an opened challenge. Functionalization is one of the possibilities to enhance processability by introducing solvent compatible functional groups. We have developed one-pot reaction procedure for a preparation and in-situ functionalization of GNRs stacks from commercially available multiwalled carbon nanotubes (MWCNTs).[1] In the first step MWCNTs are longitudinally unzipped leaving activated carboanionic edges. Activated edges can then react with electrophiles or protons in the second step, yielding edge functionalized GNRs stacks or H-terminated GNRs respectively.

Using iodoalkanes as electrophiles we have prepared alkylated GNRs.[1] Similarly, we have also prepared polymer-functionalized GNRs by adding vinyl or epoxide monomers in the second step.[2] Edge functionalized alkylated GNRs or polymerfunctionalized GNRs showed greatly enhanced solubility in organic solvents without sacrificing a single ribbon conductivity. To enhance a bulk conductivity we have intercalated iron between functionalized graphene nanoribbon stacks.[3] Iron intercalated and edge-functionalized graphene nanoribbon stacks (Fe@F-GNRs) were then aligned in a magnetic field. Aligning the ribbons greatly enhanced bulk conductivity and electrical

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1,2

Functionalization of Graphene Nanoribbon Stacks

percolation at given concentrations in previously non-conductive solvents.

Above mentioned procedures can be easily scaledup. Thus together with greatly improved processability, preserved conductivity and enhanced electrical percolation these materials could be of great interest for energy related devices, transparent touch screens, carbon fiber spinning, coating and polymer composites.

Achieving enhanced electrical percolation at a given concentration, could also have an impact on volume and mass capacity of energy related devices such as in Li-ion batteries or ultracapacitors and conductive polymer composites. Further, this method is a costeffective and potentially industrially scalable.

References [1] B. Genorio, W. Lu, A. M. Dimiev, Y. Zhu, A.-R. O. Raji, B. Novosel, L. B. Alemany, and J. M. Tour, ACS Nano, vol. 6, no. 5 (2012), 4231– 4240.

[2] W. Lu, G. Ruan, B. Genorio, Y. Zhu, B. Novosel, Z. Peng, and J. M. Tour,, “Functionali ed Graphene Nanoribbons via Anionic Polymerization Initiated by Alkali MetalIntercalated Carbon Nanotubes” submitted.

[3] B. Genorio, Z. Peng, W. Lu, B. K. P. Hoelscher, B. J. Novosel, and J. M. Tour, ACS Nano, vol. 6, no. 11 (2012), 10396–10404.

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Figures

unzipping

â&#x20AC;&#x201C;

in-situ

GNRs

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Figure 1: Proposed one-pot functionalization scheme.

Oral Graphene- A market perspective

Khasha Ghaffarzadeh R. Das and H. Zervos

IDTechEx Ltd, Downing Park, Station Road, Swaffham Bulbeck, Cambridge, CB25 0NW, UK khasha@IDTechEx.com

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Graphene is a hot topic. It promises to offer the best possible material properties in almost all applications. Its extraordinary performance has led many to call it the ‘superlative’ or ‘wonder’ material.

There are many indicators that suggest graphene is reaching the peak of its hype cycle. There has been the launch of the first-generation of products, the completion of first round of funding and a mushrooming of start-up formations. The IP patenting activity has also been rapidly rising. In the background, there has been an intense press full of praise. IDTechEx will argue that there are indications that graphene is moving past its peak of hype cycle, but slowly.

IDTechEx will argue that the graphene market is poised to grow to become a fragmented market and the fault lines of fragmentations will be the multiplicity of graphene types, manufacturing techniques and target markets. There are many companies claiming that they produce graphene, but none is producing the same material. There are also many manufacturing techniques, but each produces a different graphene quality and has a different cost structure and volume production capacity. Each market will also have different performance requirements and cost tolerance levels. IDTechEx will bring order to this fragmented and complex picture by linking target markets with graphene types and manufacturing techniques.

Today, the main market driver has been the R&D sector. In this talk, we present a perspective on future markets beyond R&D. We assess the value proposition of each type of graphene for use in/as transparent electrodes, smart packaging, RFIDs, transistors, energy storage, etc. For each market, we will outline the market needs and drivers, and the principle go-to-market strategies. Here, we will

highlight challenges, including those set by the incumbent technologies where appropriate. In all our analysis, we will emphasize the interplay between potential target markets and the manufacturing technique. We will finally give our 5-year forecast for graphene markets by application.

Figures

Figure 1: The hype cycle of graphene. Graphene is hyped but it is moving past the peak of inflated expectations.

Figure 2: Investment in graphene companies.

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Figures

Figure 3: Ordering different graphene manufacturing techniques as a function of graphene quality, cost and scalability.

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Figure 4: A chart ordering various supercapacitor applications on the basis of two parameters: 1) the strength of the value proposition of super capacitors and 2) the size restriction. Graphene will deliver the most value in blue triangle.

Oral Atomic scale structural and electronic properties of epitaxial graphene on different SiC orientations

1

Filippo Giannazzo 1 I. Deretzis , A. La Magna1 1 1 G. Nicotra , C. Spinella F.Roccaforte1 2 Q.M.Ramasse and 3 R.Yakimova

1

CNR-IMM, Catania, Italy SuperSTEM Laboratory, STFC Daresbury Campus, Daresbury WA4 4AD, UK 3 IFM, Linkoping University, Linkoping, Sweden 2

Epitaxial graphene (EG) grown by controlled graphitisation of hexagonal SiC is one of the major candidates for novel graphene-based electronics.

The interface with the substrate strongly influences EG electronic properties. As an example, EG grown on a SiC (0001) surface is subjected to a

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high electron-doping (â&#x2C6;ź 1013 cm-2) originating from the interfacial C buffer layer with a partially covalent bond to the substrate [1]. As a matter of fact, EG grows on a structured substrate, which exhibits steps or facets with different size and orientations depending on the wafer off-cut angle.

Recently, many interesting effects related to the local electronic properties of graphene over these substrate features are emerging, like a local conductance degradation [2] and a reduced carrier density [3] of EG at nanosteps-edges. Furthermore, novel metal-semiconductor-metal nanostructures entirely made from graphene, based on the peculiar interaction between EG and patterned SiC steps, have been envisaged [4].

In this work, the electronic transport in EG grown on SiC (0001) substrates with different miscut angles (from on-axis to 8°-off axis) has been investigated both at microscale (on properly designed device structures) and at nanoscale (by scanning probe microscopy) [5,6,7], focusing in particular on the impact of substrate nanosteps or facets on local graphene conductance. In particular, the results of nanoscale electrical measurements, combined with atomic-resolution structural and spectroscopic characterization techniques (i.e. scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS)) shed light into the properties of EG over the steps of off-axis silicon carbide (0001) substrates. The STEM analysis, obtained at an energy below the knock-on threshold for the C

filippo.giannazzo@imm.cnr.it

atoms, evidences that the buffer layer present on the planar (0001) face gets detached from the substrate on the (11-2n) facets of the steps, turning into a quasi-freestanding graphene film.

Simultaneously, high energy resolution atomic scanned EELS reveals that this layer has the same electronic configuration as a purely sp2-hybridized graphene layer. This aspect fully explains the observed local increase of EG resistance over SiC facets, due to a significantly lower substrateinduced doping.

References [1] F. Varchon, et al., Phys. Rev. Lett. 99 (2007) 126805.

[2] S.-H. Ji, et al., Nature Mater. 11 (2011) 114.

[3] K. Grodecki, et al., Appl. Phys. Lett. 100 (2012) 261604.

[4] J. Hicks, et al., Nature Physics (2012), DOI: 10.1038/NPHYS2487.

[5] S. Sonde, et al., Phys. Rev. B 80 (2009) 241406(R).

[6] F. Giannazzo, et al., Nano Lett. 11 (2011) 4612.

[7] F. Giannazzo, et al., Phys. Rev. B 86 (2012) 235422.

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Figures

Figure 1: Surface morphology (a) and the corresponding current map (b) measured by conductive atomic force microscopy on the as-grown EG/4H-SiC(0001) sample. Line-profiles of the height (c) and of the current (d) along the indicated directions in the maps. A significant decrease (from 1 to 0.4 μA, i.e. more than a factor of two) in the local current measured on the (11-2n) facets with respect to the values measured on the (0001) basal plane terraces can be observed.

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Figure 2: EELS spectra (left) and simultaneously acquired HAADF STEM image (right) on a cross sectioned epitaxial graphene sample grown on a facetted 4H-SiC (0001) surface. The EELS spectrum clearly shows that the buffer layer in the region immediately above the (0001) plane exhibits a stronger σ*/π* ratio than the first cabon layer above the (11-2n) surface. This is a direct demonstration that the buffer layer present on the planar (0001) face gets detached from the (11-2n) facets, turning into a quasifreestanding graphene film

Invited Tuneable magnetism in graphene

Irina V. Grigorieva

School of Physics and Astronomy, University of Manchester, UK

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I will review our recent experiments on inducing and controlling magnetic response of graphene via introduction of point defects such as vacancies and adatoms. Graphene is hailed as potentially an ideal material for spintronics due to its weak spin-orbit interaction and the ability to control its electronic properties by the electric field effect. We have demonstrated that point defects in graphene both vacancies and adatoms â&#x20AC;&#x201C; carry magnetic moments, leading to pronounced paramagnetic behaviour that dominates grapheneâ&#x20AC;&#x2122;s lowtemperature magnetism. Even better, we show that the defect magnetism is itinerant (i.e. due to localisation of conduction electrons) and can be controlled by doping, so that the induced magnetic moments can be switched on and off. This not only adds important functionality to potential graphene devices but also has important implications for spin transport.

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Oral 1

Proximity Effects Induced in Graphene

by Magnetic Insulators: FirstPrinciples Calculations on Spin Filtering and Exchange-Splitting Gaps

Ali Hallal 1 H. X. Yang 1 D. Terrade X. Waintal2 3,4 S. Roche and 1* M. Chshiev

1

mair.chshiev@cea.fr

SPINTEC, CEA/CNRS/UJF-Grenoble, INAC, 17 rue des Martyrs, 38054 Grenoble, France SPSMS-INAC-CEA, 17 rue des Martyrs, 38054 Grenoble, France CIN2 (ICN-CSIC) and Universitat Autonoma de Barcelona, Catalan Institute of Nanotechnology, Campus de la UAB, ES-08193 Bellaterra (Barcelona), Spain 4 ICREA, Institucio Catalana de Recerca i Estudis Avancats, ES-08010 Barcelona, Spain 2 3

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which gives gap widths of =98meV and =134meV for minority and majority states, respectively, while the Fermi velocities v =1.40x106 m/s and v =1.15x106 m/s are also polarized [inset of Fig. 2]. The corresponding polarization, around 20% for both gaps and velocities, is very significant [8]. We also simulated the situation of internal pressure and strain by calculating the electronic properties as a function the interlayer spacing z as described in Figs. 1(a) and 1(c). It is found [8] that the impact on the band dispersion of graphene is markedly strong [Fig. 3]. When compressing the bilayer by 0.5Å, more electrons (and spins) are transferred to the graphene layer due to enhanced overlap between C pz and Eu 4f orbitals. Accordingly, the Dirac point is moved deeper inside the valence bands compared to the equilibrium situation [cf.

Figs. 2 and 3(a)]. In contrast, for larger layer separation, the Dirac cone is clearly seen to be shifted out from the valence band of EuO, approaching the Fermi level of the system [Figs.

3(b) and 3(c)]. Simultaneously, with the shifting of the Dirac point out of the EuO valence band, the gap between spin-up and spin-down bands is continuously reduced. Finally, for z =5Å, the spinup and spin-down branches become almost degenerated and the Dirac point crosses the Fermi level, i.e., approaching a typical band structure characteristics of isolated graphene [Fig. 3(d)].

This work was supported by the Nanosciences Foundation in Grenoble, France, by French

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band gap opening at the Dirac point [Fig. 2].

Interestingly, the degeneracy lifting at the Dirac point is spin dependent as can be demonstrated with a simple fit of the band structure with spindependent Dirac dispersion relation

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Graphene is very attractive for spintronics [1] since long spin lifetimes are expected within this material due to its intrinsic weak spin-orbit coupling and hyperfine interaction [2]. However, inducing magnetism in graphene is still jeopardizing for its applications. One way to induce magnetic states in graphene is using magnetic substrates, e.g. transition metals Co and Ni [3]. The properties of these epitaxial films have been extensively studied, however they are grown on conducting substrates which limit grapheme applications for electronic devices. Alternative possibility is to use magnetic insulating material EuO as a substrate [4]. Here we addressed this problem from first principles and report promising potential for producing high spin polarization and exchange splitting band-gap values. Our calculations were performed using density functional theory based VASP [5] and SIESTA [6] packages. Considering that Eu is a heavy element and its outer shell (4f76s2) contains f electrons, GGA approach fails to describe strongly correlated localized 4f electrons giving the metallic ground state of EuO, while a clear band gap is observed in experiment [7]. Thus, we introduced Hubbard-U parameter to describe the strong intraatomic interaction in a screened Hartree-Fock like manner, which produces correct ground state of EuO. Using the optimized structure of graphene on EuO [Fig. 1], we found that the interaction with the magnetic substrate remarkably affects the magnetic properties of graphene [8]. First, a spin polarization defined as a difference between minority and majority states normalized by the total density of states at the Fermi level may reach 24% [8]. Next, the traditional linear dispersion of the graphene band structure is modified yielding a

National Research Agency (ANR) Projects NANOSIM_GRAPHENE, and by European Union funded STREP Project CONCEPT-GRAPHENE.

References [1] A. Fert et al, Mat. Sci. Eng. B, 84 (2001) 1; S. A. Wolf et al, Science, 294 (2001) 1488.

[2] D. Huertas-Hernando et al, Eur. Phys. J. Special Topics, 148 (2007) 177.

[3] A. Varykhalov et al, Phys. Rev. Lett., 101 (2008) 157601; O. Rader et al, Phys. Rev. Lett., 102 (2009) 057602.

[4] H. Haugen et al, Phys. Rev. B, 77 (2008) 115406.

[5] G. Kresse and J. Hafner, Phys. Rev. B, 47 (1993) 558; P. E. Blöchl, Phys. Rev. B 50 (1994) 17953; G. Kresse and J. Joubert, ibid. 59 (1999) 1758.

[6] J. M. Soler, E. Artacho, J. D. Gale, A. Garcı`a, J. Junquera, P. Ordejo´n and Daniel Sa´nchezPortal, J. Phys. Condens. Matter 14, 2745 (2002).

[7] N. J. C. Ingle et al, Phys. Rev. B., 77 (2008) 121202; A Mauger et al, Phys. Reports, 141 (1986) 51.

[8] H. X. Yang, A. Hallal, D. Terrade, X. Waintal, S. Roche and M. Chshiev, Phys. Rev. Lett. 110, 046603 (2013).

Figures

Figure 2: Band structure of graphene on EuO. Green (blue) and black (red) represent spin up and spin down bands of EuO (graphene), respectively. Inset: zoom around the Dirac cone, the symbols correspond to DFT data while the lines correspond to the fit according to Eq. (2).

Figure 3: Band structures for graphene on EuO with graphene shifted (a) inward (compared to optimized structure) 0.5A, (b) outward 1.0A, (c) outward 2.0 A, and (d) outward 5.0 A, respectively.

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Figure 1: (a) side view and (b) top view of the calculated crystalline structures for graphene on top of a six bilayer EuO film. The bottom of EuO is terminated with hydrogen atoms. (c) relative energy (to the optimized structure) of graphene- EuO as a function of shifting distance (_Z) between the graphene and the substrate.

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Oral Contacting atomically well-defined graphene nanoribbons with atomic scale precision 1

Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, PO Box 80000, 3508 TA Utrecht, the Netherlands 2 COMP Centre of Excellence and Helsinki Institute of Physics, Department of Applied Physics, Aalto University School of Science, PO Box 14100, 00076 Aalto, Finland 3 Department of Applied Physics, Aalto University School of Science, PO Box 15100, 00076 Aalto, Finland

Graphene nanostructures, where quantum confinement opens an energy gap in the band structure, hold promise for future electronic devices. Realizing novel functions will require exquisite, atomic scale control over the contacts to graphene and the graphene nanostructure forming the active part of the device. The contacts should have a high transmission and yet not modify the electronic properties of the active region significantly to maintain the potentially exciting physics offered by the nanoscale honeycomb lattice. Here, we show how contacting an atomically well-defined graphene nanoribbon (GNR) to a metallic lead by a chemical bond via only one atom significantly influences the charge transport through the GNR but does not affect its electronic structure. We form atomically welldefined contacts between the GNR and the gold substrate by removing individual hydrogen atoms from the end of a GNR. We use combined AFM and STM to link the changes in the chemical structure to the changes in the electronic properties. The dramatically increased coupling between the GNR and the lead manifests itself through the suppression of inelastic transport channels. The experiments are in a perfect agreement with the theoretical calculations.

2

Ari Harju 1 J. van der Lit , 1 M. P. Boneschanscher D. Vanmaekelbergh1 2 2 M. Ijäs , A. Uppstu 2 3 M. Ervasti , P. Liljeroth 1 and I. Swart ari.harju@aalto.fi

Figures

Figure 1: Controlled atomic scale modification of the GNR reduces vibronic coupling. a), High-resolution STM image of a free GNR (V = 50 mV, I = 5 pA). b), High-resolution STM image after a bias pulse has been used to modify the left end of the GNR (V = 50 mV, I = 20 pA). c), d) Zoomed-in STM images of the GNR ends after the modification (c: V = 50 mV, I = 50 pA, d: V = 10 mV, I = 2 pA). e), atomically resolved AFM image of the contacted GNR. f), AFM image of the same ribbon as in (e), but with the tip 80 pm closer to the sample. g),h) dI/dV spectra recorded at the left and right ends of the GNR before (blue) and after (red) of the modification. All the images have been acquired with a CO-terminated tip. Scale bars: 0.5 nm.

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[1] Joost van der Lit, Mark P. Boneschanscher, Daniël Vanmaekelbergh, Mari Ijäs, Andreas Uppstu, Mikko Ervasti, Ari Harju, Peter Liljeroth, Ingmar Swart,, Submitted (2013).

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References

Oral N-doped graphene: Electronic properties and STM

luc.henrard@fundp.ac.be

University of Namur, Namur, Belgium

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In this communication, simulations of the electronic properties and of STM-STS results of Ndoped graphene are presented and compared with experimental data. Indeed, chemical modification and, in particular nitrogen doping, is one of the major route to tailor the electronic and optical properties of graphene materials. However, the control of the doping atomic configuration is still a challenge and the exact consequences on the physical properties of each configurations is far from being fully understood. Here, we review our recent achievements on this topic with an emphasis on the input of simulations to understand the effect of the long-range interaction between dopant and of the layer stacking on the electronic properties and STM/STS fingerprints.

Post-synthesis N-doping of graphene have been performed by plasma exposure of C-terminated SiC wafer [1]. STM pattern are similar to those obtained by other methods and, for more than 75 % of the doping sites, have been attributed to the substitution of one C atom by an N atom (See Fig 1 for the STM/STS analysis). Other (and more complex) patterns have been images at several sample-tip bias, demonstrated hole doping configurations. Experimental STM reveals that the N-doping pattern depends on the tip-graphene distance and we have performed detailed STM simulations in order to rationalize this observation (For more details, see [1]).

Being a true 2D crystal, graphene has special properties. In particular,a point-like defect may introduce perturbations in the long range. This characteristic questions the validity of using a supercell geometry in an attempt to explore the properties of isolated defect. Fig 2 b and c demonstrate this effect for DFT simulations for a single N substitution in a 9x9 (0.6 %of N) and

Luc Henrard F. Joucken S.O. Guillaume R. Sporken and Ph. Lambin

10x10 graphene supercell (0.5% of N), as compared to tight-binding approach for an isolated N 'defect' in a infinite graphene layer (Fig 2a). We have also shown that a doping of graphene with a random (not periodic) distribution of dopant has a electronic structure very similar to isolated defect and not to the regularly spaced defect with the same dopant concentration. The dopant concentration has then less importance that the periodicity for low concentration. Of course, as soon as dopant are a few nanometer apart, interaction occurs and the STM pattern become more complicated to analyze (For more details, see [2]).

Chemical doping has also been investigated for bilayer graphene. Here, we show that a charge transfer occurs between the two layers, even if only one of the two layers is doped. In this case, if the 'pristine' graphene layer is analyzed with STM, no local pattern is found but the symmetry of the grapheme pattern (hexagonal or triangular) is modified by the doping level. If the doping occurs on the top layer, the STM pattern is slightly dependent on the doping sub-network site (For more details, see [3]).

References [1] F. Joucken, Y. Tison, J. Lagoute, J. Dumont, D. Cabosart, B. Zheng, V. Repain, C. Chacon, Y. Girard, A. R. Botello-Mendez, S. Rousset, R. Sporken, J.-C. Charlier, and L. Henrard, Phys.

Rev. B, 85 (2012)161408.

[2] Ph. Lambin, H. Amara, F. Ducastelle, L. Henrard. Phys. Rev. B 86 (2012) 045448.

[3] S.O. Guillaume, B. Zheng, J.-C. Charlier, L. Henrard. Phys. Rev. B 85 (2012) 035444.

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Figures

Figure 1: Top: Topographic images of a substitutional nitrogen atom at (a) Vs = +0.2 V, I = 200 pA, (b) Vs = −0.2 V, I = 100 pA, (c) Vs = +0.5 V, I = 700 pA, (d) Vs = −0.4 V, I = 100 pA, and (e) Vs = +0.35 V, I = 800 pA. (e) Schematic view, (f) and (g) Simulations for N substitution in a 10x10 graphene supercell at (f) Vs = +0.5 V and (g) Vs = −0.5 V. Bottom left: Experimental Scanning tunneling spectra between graphene (black curve) and the simple substitution (red curve).

Spectra taken with the feedback loop active when moving from one spot to another. Inset: Spectra taken with the feedback loop off when moving from one spot to another. Bottom right: Partial DOS of isolated Ndoped graphene. From refs [1,2].

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Figure 2: Partial Density of States of substitutional N-doped graphene. (a) Tight-binding calculations for an isolated N atom in a infinite graphene sheet. (b) and (c ) DFT calculations of a N atom in a (9x9) and (10x10) supercell. From ref [2].

Invited Nanoelectronic Properties and Applications of Chemically Modified Graphene

Mark C. Hersam

m-hersam@northwestern.edu

Department of Materials Science and Engineering, Northwestern University 2220 Campus Drive, Evanston, IL 60208-3108, USA http://www.hersam-group.northwestern.edu/

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The outstanding electronic transport properties of graphene, including its superlative charge carrier mobilities, have been established on pristine samples in idealized conditions. However, for nanoelectronic applications, graphene needs to be interfaced with other materials in a manner that either preserves its intrinsic properties or modifies its properties in a manner that enhances functionality [1]. Towards these ends, this talk focuses on chemical functionalization strategies for interfacing graphene with other materials and for tailoring its electronic properties. For example, several noncovalent chemistries have been demonstrated and characterized at the molecular scale with ultra-high vacuum (UHV) scanning tunneling microscopy (STM) including 3,4,9,10perylenetetracarboxylic dianhydride (PTCDA) [2-4] and 10,12 pentacosadiynoic acid (PCDA) [5].

PTCDA is shown to be an effective atomic layer deposition (ALD) seeding layer for high-k dielectrics (e.g., Al2O3 and HfO2) such that the PTCDA monolayer remains intact as a well-defined passivating layer at the graphene-dielectric interface following ALD [6-8]. On the other hand, PCDA forms one-dimensionally ordered selfassembled monolayers on graphene. The PCDA can then be stabilized by ultraviolet photopolymerization, yielding one-dimensional polymers with sub-2 nm widths that are in registry with the underlying graphene lattice [3]. These ordered cross-linked PCDA-based polymers are promising templates for one-dimensional ALDgrown oxide nanostructures [9]. Beyond noncovalent self-assembled monolayers, this talk will also explore covalent modification schemes for graphene based on free radical chemistries [10]. In particular, atomic oxygen has been established as an effective method for homogeneously

functionalizing graphene with epoxide groups in UHV [11].

Importantly, this covalent functionalization method is fully reversible under mild thermal annealing conditions (~ 260ยบC) as shown by atomic resolution UHV STM imaging. In addition to chemically doping graphene, epoxidation yields local modification of the graphene bandstructure and provides multiple pathways for further chemical functionalization [12].

References [1] Q. H. Wang and M. C. Hersam, MRS Bulletin, 36, 532 (2011).

[2] Q. H. Wang and M. C. Hersam, Nature Chemistry, 1, 206 (2009).

[3] Q. H. Wang and M. C. Hersam, Nano Letters, 11, 589 (2011).

[4] J. D. Emery, et al., Surface Science, 605, 1685 (2011).

[5] A. Deshpande, et al., Journal of the American Chemical Society, 134, 16759 (2012).

[6] J. M. P. Alaboson, et al., ACS Nano, 5, 5223 (2011).

[7] J. E. Johns, et al., Journal of Physical Chemistry Letters, 3, 1974 (2012).

[8] V. K. Sangwan, et al., Nano Letters, 13, 1162 (2013).

[9] J. M. P. Alaboson, et al., Nano Letters, in press, DOI: 10.1021/nl4000932 (2013).

[10] Md. Z. Hossain, et al., Journal of the American Chemical Society, 132, 15399 (2010).

[11] Md. Z. Hossain, et al., Nature Chemistry, 4, 305 (2012).

[12] J. E. Johns and M. C. Hersam, Accounts of Chemical Research, 46, 77 (2013).

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Oral Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics 1

Chair for Applied Physics, Friedrich-Alexander University Erlangen-Nuremberg, Staudtstr. 7, 91058 Erlangen, Germany 2 ACREO AB, Electrum 236, Isafjordsgatan 22, 16440 Kista, Sweden

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D. Waldmann1, J. Jobst1 A. Albert1, M. Albrecht1 A. Glas1, S. Reshanov2 S. Preu1, A. Schöner2 M. Krieger1 and H. B. Weber1

Stefan.Hertel@FAU.de

References [1] Hertel, S. et al., Nature Communications 3 (2012) 957.

[2] Hertel, S. et al., Applied Physics Letters 98 (2011) 212109.

[3] Balandin, A. A., Nature Materials 10 (2011) 569.

[4] Mayorov, A. S. et al., Nano Letters 11 (2011) 2396.

[5] Lin, Y.- M. et al., Science 332 (2011) 1294.

[6] Lemme, M. C., Solid State Phenomena 156– 158 (2009) 499.

[7] Emtsev, K. V. et al., Nature Materials 8 (2009) 203.

[8] Pensl, G. et al., International Journal of High Speed Electronics and Systems 15 (2005) 705.

[9] Riedl, C. et al., Physical Review Letters 103 (2009) 246804.

Figure 1: Artist's impression of a monolithic epitaxial graphene transistor. Current flows from as-grown monolayer graphene (blue) through an ohmic interface into the silicon carbide (SiC) channel (cyan). The quasi-freestanding bilayer graphene (red) provides a Schottky-like contact to the conducting SiC layer, which can be pinched of by the corresponding space charge region.

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Figures

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Graphene has many favorable properties for future electronics, e.g. extremely high current stability [2], high thermal conductivity and temperature stability [3] and excellent charge carrier mobility [4]. The latter should result in fast transistors, which have already been demonstrated [5].

However, due to the missing gap in graphene's band structure it is fairly hard to design an efficient switch for logic applications [6].

As epitaxial graphene grown by thermal decomposition of silicon carbide (SiC) (0001) [7] is intimately connected to the SiC we consider the bare graphene layer together with the substrate and their common interface as one material system, in which SiC provides a wide-bandgap semiconductor [8], and graphene acts as a metal.

There, the graphene physics come into play: due to its atomically thin shape, the interface tunes its Fermi level, which is not possible for other metals.

We are able to tailor that interface to form ohmic and Schottky-like contacts by means of hydrogen intercalation [9].

We developed a scheme to fabricate both interface types side by side on the same chip leading to a monolithic epitaxial graphene transistor with ON/OFF ratios exceeding 104 under ambient conditions (Fig. 1). We proof the concept’s capability for logics by presenting an integrated inverter (Fig. 2) as well as NAND and NOR gates without any additional components.

Using a Schottky diode built within the same fabrication scheme, and connected to two suitable antennae, we are able to realize a fast andefficient THz detector.

1

Stefan Hertel

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Figure 2: Voltage transfer characteristic of an inverter. VIL and VIH indicate noise margins for the input signal.

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Oral A novel class of strain gauges based on layered percolative films of 2D materials

Mario Hofman M. Hempel D. Nezich and J. Kong

Mario@mail.ncku.edu.tw National Cheng Kung University, Department of Materials Science and Engineering, 1 University Rd, Tainan, Taiwan

Here we report on the fabrication and characterization of a novel type of strain gauge based on percolative networks of two-dimensional materials. The high sensitivity of the percolative carrier transport to strain induced morphology changes was exploited in strain sensors that can be produced from a wide variety of materials. Highly reliable and sensitive graphene-based thin film strain gauges were produced from solution processed graphene flakes by spray deposition.

Control of the gauge sensitivity could be exerted through deposition-induced changes to the film morphology. This exceptional property was explained through modeling of the strain induced changes to the flake-flake overlap for different percolation networks. The ability to directly deposit strain gauges on complex-shaped and transparent surfaces was presented. The demonstrated scalable fabrication, superior sensitivity over conventional sensors, and unique properties of the described strain gauges have the potential to improve existing technology and open up new fields of applications for strain sensors.

Figures

References

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[1] Nano Lett. 2012 Nov 14;12(11):5714-8.

Oral Probing the Limits of Graphene Metal Coatings

Liv Hornekaer

iNANO, Aarhus University, Ny Munkegade Bygn. 1520, Aarhus, Denmark

liv@phys.au.dk

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Graphene combines several exceptional properties, which makes it uniquely suited as a coating material [1-2]: excellent mechanical stability, low chemical reactivity, impermeability to most gasses, transparency, flexibility as well as very high thermal and electrical conductivity.

Moreover, graphene can be grown directly on a range of metal surfaces and is even able to cover step edges and small defects in metal surfaces in a carpet like fashion [3-5]. Here, we investigate the limitations of graphene as an effective corrosioninhibiting coating on metal surfaces by scanning tunneling microscopy measurements and density functional theory calculations. Specifically, the hexreconstructed Pt(100) surface is used an a probe system, since exposure of small molecules directly onto this surface will lift the reconstruction, thus allowing for in situ monitoring of coating breakdown[6].

STM measurements reveal that a single graphene layer acts as an effective coating protecting the reactive hex-reconstructed Pt(100) surface from O2 exposure, and thus preserving the reconstruction underneath the graphene layer in O2 pressures as high as 10-4 mbar. A similar protective effect against CO is observed at CO pressures below 10-6 mbar. However, at higher pressures CO is observed to intercalate under the graphene coating layer, thus lifting the reconstruction, without damaging the graphene layer.

The limitations of the coating effect are further tested by exposure to hot atomic hydrogen. While the coating can withstand these extreme conditions for a limited amount of time, after substantial exposure, the Pt(100) reconstruction is lifted. Anneal experiments and density functional theory calculations demonstrate that the basal plane of the graphene stays intact and point to a

L. Nilsson, M. Andersen R. Balog, E. Lægsgaard P. Hofmann, F. Besenbacher B. Hammer and I. Stensgaard

grapheme mediated mechanism for the H-induced lifting of the reconstruction.

References [1] Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A., Electric Field Effect in Atomically Thin Carbon Films. Science 306 (2004), 666-669.

[2] Geim, A. K.; Novoselov, K. S., The Rise of Graphene. Nat. Mater. 6 (2007), 183-191.

[3] Coraux, J.; N'Diaye, A. T.; Busse, C.; Michely, T., Structural Coherency of Graphene on Ir(111). Nano Lett. 8 (2008), 565-570.

[4] Wintterlin, J.; Bocquet, M. L., Graphene on Metal Surfaces. Surf. Sci. 2009, 603, 18411852.

[5] Nilsson, L.; Andersen, M.; Bjerre, J.; Balog, R.; Hammer, B.; Hornekær, L.; Stensgaard, I., Preservation of the Pt(100) Surface Reconstruction after Growth of a Continuous Layer of Graphene. Surf. Sci. 606 (2012), 464469.

[6] Louis Nilsson, Mie Andersen, Richard Balog, Erik Lægsgaard, Philip Hofmann, Flemming Besenbacher, Bjørk Hammer, Ivan Stensgaard and Liv Hornekær, ACS NANO 6 (2012),1025810266.

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Figures

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Figure 1: STM image of a Pt(100) surface partially coated by graphene. For all images, the terrace at the right side is uncoated, whereas the rest is coated by graphene (indicated by a blue boundary). The partially coated surface is exposed to (a) 0 L, (b) 3 L and (c) 63 L of CO. All the images have been differentiated to enhance the contrast. Imaging conditions [Vt , It]:[4.6 mV, 0.44 nA].

Reproduced from ref. 6.

Oral Graphene Crystal Growth Engineering on Epitaxial Copper Thin Films

Robert M. Jacobberger M. S. Arnold

jacobberger@wisc.edu Department of Materials Science and Engineering University of Wisconsin-Madison, Madison, Wisconsin, United States

100

In this work [1], we study graphene growth dynamics on epitaxial Cu thin film substrates by chemical vapor deposition (CVD). These surfaces have a single crystallographic orientation and are atomically smooth, unlike their foil counterparts, making them better platforms on which to reproducibly synthesize highquality graphene and study crystal growth evolution.

Consequently, we gained novel insight into the key mechanisms and factors that influence graphene growth dynamics, such as Mullins-Sekerka morphological instabilities, Cu surface orientation, hydrogen-to-methane flux ratio (H2:CH4), absolute pressure, and nucleation density. We demonstrate how the various graphene morphologies that are commonly reported in literature, such as lobes, dendrites, hexagrams, and hexagons, can be selectively synthesized over large areas by controlling critical CVD parameters. In particular, growth on Cu(111) can be tuned to yield high-quality, large-scale, singlecrystalline graphene monolayers, a feat that is not possible on Cu foil due to the rotational grain boundaries that exist when graphene islands on neighboring Cu facets merge.

Recently, there has been a tremendous effort to control graphene growth dynamics with the goal of tailoring its structure, and therefore, its properties, for specific applications. The extraordinary electronic, thermal, and mechanical properties that graphene possesses are highly dependent on its physical characteristics, including crystallinity, grain size, edge termination, and morphology. While numerous graphene morphologies with various orientations have been synthesized via CVD on polycrystalline Cu foils, the conditions that yield such structures are not well defined and the mechanisms that govern their evolution are not sufficiently understood.

This lack of understanding can be attributed to complications in analyzing growth on Cu foils due to their polycrystalline nature and high surface roughness. The numerous foil surface orientations impact growth processes differently due to unique catalytic activity and thermodynamic properties, causing local variations in growth conditions across the substrate. Here, we minimize these local deviations by conducting growth on ultra-smooth, epitaxial Cu(100), Cu(110), and Cu(111) thin

films (Figure 1) that have roughness < 1 nm over 10 × 10 2 μm areas.

We studied the morphological evolution of graphene crystals in atmospheric pressure CVD (APCVD) and low pressure CVD (LPCVD) with low H2:CH4 (Figure 2). Initially, the graphene islands are circular (Figure 2a). However, as they exceed a critical size ~ 1.0 μm, dendritic branches begin to propagate from the crystal perimeter (Figure 2bh). In LPCVD, the dendrites extend hundreds of microns in the <100>, <111>, and <110> directions on Cu(100), Cu(110), and Cu(111), respectively; whereas in APCVD, no such relationships exist, resulting in circular dendritic structures. Twin boundaries on the Cu(111) surface disrupt the preferred direction of graphene propagation in LPCVD, making the growth appear more isotropic.

Furthermore, we present evidence that the lobed islands commonly grown in LPCVD would evolve into highly dendritic structures if the inter-nucleation spacing was sufficiently large (~10 μm) (Figure 2i). This observed morphological evolution suggests that graphene growth is driven by Mullins-Sekerka morphological instabilities and is limited by mass transport.

In both pressure regimes, the dendritic nature of growth is suppressed with increasing H2:CH4, resulting in more compact islands with planar edges. In LPCVD, the dendrite tip angle increases until the branches are entirely “filled in,” resulting in squares, rectangles, circles, and hexagons on Cu(100), Cu(110), twinned Cu(111), and non-twinned Cu(111) which reflect the underlying Cu crystal symmetry (Figure 3). Twins disrupt the preferential propagation of graphene in the <110> direction on Cu(111) (Figure 3i and inset). In APCVD, the islands transition from circular dendritic structures to hexagrams to hexagons with increasing H2:CH4, regardless of the surface orientation and the presence of twins (Figure 4). The graphene domains have one orientation with respect to the Cu(111) surface, and multiple preferred orientations with respect to the Cu(100) and Cu(110) surfaces. The epitaxial nature of growth on Cu(111) provides a route to manufacture single-crystalline graphene over large scales, eliminating the rotational grain boundaries that degrade charge and heat transport through graphene and that are unavoidable with growth on Cu foils due to their polycrystallinity.

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Finally, we show that all growth regimes can result in high-quality continuous monolayer graphene with D:G Raman ratio < 0.1, demonstrating the utility of this growth technique (Figure 5) The synthetic method presented here provides a detailed roadmap to tailor the structure, orientation, and morphology of graphene over large areas. The understanding gained from this work will improve crystal growth engineering of graphene and other twodimensional materials, and will ultimately help lead to the scalable fabrication of defect-free, high-quality graphene materials with superior electrical, thermal, and mechanical properties.

References [1] Jacobberger, R. M.; Arnold, M. S., Chem. Mater., Submitted.

Figure 3: Graphene crystal morphology dependence on H2:CH4 in LPCVD. First, second, and third columns represent the island structure on Cu(100), Cu(110), and twinned Cu(111), respectively. Top, middle, and bottom rows depict island morphology at low, medium, and high H2:CH4, respectively. Scale bars are 40 μm for the first and second columns and 10 μm for the third column. As H2:CH4 is increased, the dendritic nature of growth is suppressed and the graphene islands develop into more planar shapes that reflect the underlying Cu crystallography. (i) inset demonstrates that hexagons form on non-twinned Cu(111) instead of circles.

Figures

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Figure 5: Raman data for continuous, monolayer graphene in all growth regimes. The D:G ratiois<0.1, indicating that the graphene is of highquality. The five sets of spectra, from bottom to top, correspond to dendritic growth in APCVD (blue), hexagram growth in APCVD (green), hexagon growth in APCVD (yellow), dendritic growth in LPCVD (orange), andplanar growth in LPCVD (red). The bottom, middle, and top spectra in each color set represent growth on Cu(100), Cu(110), and Cu(111), respectively.

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Figure 2: (a-h) Graphene islandmorphology evolution on Cu(100) in LPCVD with low H2:CH4. Island sizes are (a) 0.7, (b) 1.4, (c) 3.1, (d) 4.9, (e) 7.9, (f) 22, (g) 59, and (h) 115 μm. This evolution suggests that dendritic structures are caused by Mullins-Sekerka instabilities.

A similar evolution occursin APCVD with low H2:CH4, but the figure has been omitted here due to length restrictions. (i) The dendritic nature of growth is suppressed due to small inter-nucleation distance. The islands in (i) are ~ 6.0 μm in length

Figure 4: Graphene island morphology dependence on H2:CH4 in APCVD. First, second, and third columns represent the island structure on Cu(100), Cu(110), and Cu(111), respectively. H2:CH4 increases from the top to the bottom row. Scale bars are 5 μm except for 5d and 5j, which are 1 μm.

Similar to LPCVD, the dendritic nature of growth is suppressed with increasing H2:CH4. But, in APCVD, the islands evolve into hexagonallyfaceted crystals, regardless of the Cu orientation.

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Figure 1: .Atomic force microscopy topographical map of Cu films after sputtering. (a) Cu(100), (b) Cu(110), and (c) Cu(111) filmshave roughness < 1 nmover 10 × 10 μm2 areas, which is >50 times smoother than Cu foil at the samescale. Scale bars are 400 nm. (a-c) insets are electron backscatter diffraction data with red, green, and blue correspondingto Cu(100), Cu(110), and Cu(111), respectively.

Inset scale bars are 50 μm.

Oral Nitrogen doped graphene studied by STM/STS and ARPES 1

PMR, Université de Namur, Namur, Belgique MPQ, Université Parid-Diderot, Paris, France, Ligne Cassiopée, synchrotron Soleil, Saint-Aubin, France 4 GeorgiaTech, Atlanta, USA

Frédéric Joucken

1

Y. Tison2, Y. Girard2 C. Chacon2, V. Repain2 P. Le Fèvre3, A. Tejeda3 A. Taleb3, S. Rousset2 E. Conrad4, R. Sporken1 L. Henrard1, J. Ghijsen1 and J. Lagoute2

2 3

Tuning the electronic properties of low dimensional carbon materials is a current challenge for the development of carbon based technology. Doping by insertion of foreign atoms in the atomic lattice is a promising strategy to reach the control of the electronic structure of carbon materials. Nitrogen atoms are good candidates for chemical doping due to their suitable atomic radius and the additional electron that they contain as compared to carbon. They can adopt different local environments (graphitic-like, pyridinic-like) which can have various effects on the electronic structure [1].

For the particular doping method we use (i.e. exposure of the epitaxially grown graphene to an atomic nitrogen flux), we combine STM imaging and tunnelling spectroscopy [2] with AngledResolved Photoemission Spectroscopy (performed at the Cassiopée beamline at the synchrotron Soleil), to correlate the configuration of the nitrogen atoms in the graphene lattice with their observed effect on the band structure and compare it with the result of DFT-based calculations. Typical data are displayed on figure 1 where one can see an STM image, a STS spectrum and an ARPES spectrum of one sample. We also evaluate the number of charge carriers brought by each doping atom and its evolution as a function of the nitrogen concentration. We will point out difficulties in determining those quantities arising when one is dealing with heavily doped samples.

fjoucken@fundp.ac.be

[2] F. Joucken et al., Phys. Rev. B 85, (2012) 161408(R).

Figures

Figure 1: (left to right) STM image, STS spectrum and ARPES spectrum of a lightly nitrogen-doped sample.

References

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[1] B. Zheng, P. Hermet, L Henrard, ACS Nano, 7 (2010) 4165.

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Invited Properties of graphene and other lowdimensional objects obtained from imaging and spectroscopy experiments in a transmission electron microscope

Ute Kaiser

ute.kaiser@uni-ulm.de

Ulm University, Group of Electron Microscopy for Materials Science Ulm 89081, Germany

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[1] U. Kaiser, J. Biskupek, J.C. Meyer, J. Leschner, L. Lechner, H. Rose, M. Stöger-Pollach, A.N. Khlobystov, P. Hartel, H. Müller, M. Haider, S. Eyhusen and G. Benner, Ultramicroscopy, 111, 8, 1239-1246, 2011.

[2] Z.Lee, J.C.Meyer, H.Rose and U.Kaiser, Ultramicroscopy 112, 39-46, 2012.

[3] J.C. Meyer, S. Kurasch, H.J. Park, V. Skakalova, D. Künzel, A. Groß, A. Chuvilin, G. Algara-siller, S. Roth, T. Iwasaki, U. Starke, J.H. Smet and U. Kaiser, Nature Materials, 10, 209-215, 2011.

[4] J. Kotakoski, A. Krasheninnikov, U. Kaiser and J. Meyer, Physical Review Letters, 106, 10, 2011.

[5] J] J C Meyer, F Eder, S Kurasch, V Skakalova, J Kotakoski, H-J Park, S Roth, A Chuvilin, S Eyhusen, G Benner, A V Krasheninnikov, U Kaiser Physical Review Letters, 108, 196102.

2012.

[6] H P Komsa, J Kotakoski, S Kurasch, O Lehtinen, U Kaiser, A V Krasheninnikov, Physical Review Letters 109, p. 035503, 2012.

[7] O Lethinen, S Kurasch, AV Krasheninnikov, U Kaiser submitted.

[8] S. Kurasch, J. Kotakoski, O. Lehtinen, V. Skakalova, J. H. Smet, C. Krill III, A. V. Krasheninnikov, U. Kaiser, Nano Lett. 12 (6), 3168–3173, 2012.

[9] ] P. Y. Huang, S. Kurasch, A. Srivastava, V. Skakalova, J. Kotakoski, A. V. Krasheninnikov, R. Hovden, Q. Mao, J. C. Meyer, J. Smet, D. A. Muller, and U. Kaiser, Nano Letters 12(2), 1081-1086, 2012.

GRAPHENE 2013

References

103

The atomic structure and electronic properties of graphene and other low-dimensional objects are obtained by analytical low-voltage aberration-corrected high-resolution transmission electron microscopy [1,2]. We investigate in-situ electron beam-induced modifications of graphene functionalized by dopants [3], defects [4] or molecules. We discuss the determination of knock-on damage thresholds in two-dimensional objects [5,6] and how, under the influence of the electron beam, point defect cluster and dislocation form and annihilate [7] and how grain boundaries migrate on the atom-by-atom base [8]. Moreover we discuss structural changes under the influence of Joule heating and address the basic question how the amorphous phase of 2D objects is formed and can it can be described from direct images [9,10].

We discuss then electron-beam-induced transformation route of different nano-carbon structures [11,12]. Most of our experiments were combined by atomistic simulations.

In the spectroscopy mode we show that the monochromatic low-energy electron beam enables the acquisition of EELS spectra with exceptionally low background noise [1]. In addition to the energy of electronic excitations, also the momentum information can be accessed in a TEM. We determine the dispersion behavior for π and π+σ plasmons in free-standing singlelayer graphene [13] and multilayers with increasing thickness (number of layers).

In addition, we report on the property of graphene as substrate for transmission electron microscopy and – furthermore - to sandwich electron-beam sensitive materials protecting it similarly to a carbon nanotube.

104

[10] ] B. Westenfelder, J. C. Meyer, J. Biskupek, S. Kurasch, F. Scholz, C. E. Krill III and U. Kaiser, Nano Letters, 11 (12), 5123-5127, 2011.

[11] A Chuvilin, U Kaiser, E Bichoutskaia, N Besley and AN Khlobystov, Nature Chemistry, 2 (2010), p. 450.

[12] A. Chuvilin, E. Bichoutskaia, M. C. GimenezLopez, T. W. Chamberlain, G. A. Rance, N. Kuganathan, J. Biskupek, U. Kaiser and A. N. Khlobystov, Nature Materials, 10, 687-692, 2011.

[13] , M. K. Kinyanjui, C. Kramberger, T. Pichler, J. C. Meyer, P. Wachsmuth, G. Benner and U. Kaiser, EPL 97, 57005, 2012.

[14] Fruitful cooperation within the SALVE project and financial support by the DFG (German Research Foundation) and by the Ministry of Science, Research, and the Arts (MWK) of Baden-W端rttemberg are gratefully acknowledged.

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Oral Highly Efficient Electrodes for Dye Sensitized Solar Cells Based on Graphene Oxide

1

Ladislav Kavan 2 J. - H. Yum and 2 M. Graetzel

kavan@jh-inst.cas.cz 1

J. Heyrovsky Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, CZ-18223 Prague 8, Czech Republic 2 Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland

[1] B. E. Hardin, H. J. Snaith, M. D. McGehee, Nature Photonics 6, 161 (2012).

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GRAPHENE 2013

References

[2] K.Kalyanasundaram, Dye Sensitized Solar Cells, CRC Press Taylor & Francis, Boca Raton, 2010.

[3] A. Yella, H. W. Lee, H. N. Tsao et al., Science 334, 629 (2011).

[4] J.-H. Yum, E. Baranoff, F. Kessler et al., Nature Comm. 3, 631 (2012).

[5] L. Kavan, J.-H. Yum, M. K. Nazeeruddin et al., ACS Nano 5, 9171 (2011).

[6] L. Kavan, J.-H. Yum, M. Gr채tzel, Nano Lett. 11, 5501 (2011).

105

The dye sensitized solar cell (DSC) is an attractive alternative to solid state photovoltaics [1,2]. The generic device is a photoelectrochemical DSC with sensitized nanocrystalline titanium dioxide photoanode, electrolyte solution with a redox mediator and the counterelectrode. The latter is typically a film of Pt nanoparticles on F-doped tin oxide (FTO) and the former is the triiodide/iodide couple in aprotic electrolyte medium. Recently, this couple was exchanged with Co(III/II)-based redox mediators [3,4]. The obvious motivation consisted in enhancing the voltage of DSC. Graphene nanoplatelets (GNP) exhibit high electrocatalytic activity for Co(III/II) based mediators [5,6]. Graphene oxide (GO) showed almost no activity as DSC cathode, resembling the properties of basal plane pyrolytic graphite.

However, the activity of GO improved dramatically upon reduction with hydrazine and/or heat treatment. The reduced GO or GO/GNP composite films are favored by excellent adhesion to FTO and by higher stability against aging. All GO-containing films were firmly bonded to FTO which contrasted with the poor adhesion of sole graphene nanoplatelets to this support. The activity loss during long-term aging was considerably improved, too. Enhanced stability of GO-containing films together with high electrocatalytic activity is beneficial for application in a new generation of dye-sensitized solar cells employing Co(bpy)33+/2+ as the redox shuttle.

Invited Graphene Flagship Working together to convert scientific excellence to technological impacts

Jari Kinaret

jari.kinaret@chalmers.se

Chalmers University of Technology, Gothenburg, Sweden

106

In this talk I will describe the Graphene Flagship, its origin, present status and future plans. I will concentrate on the implementation issues rather than going into technical details of the planned research work.

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Oral 2D Transition-Metal Dichalcogenides: Doping, Alloying and Atomic Structure Engineering Using Electron Beam

Arkady V. Krasheninnikov 2 H. - P. Komsa 3 S. Kurasch J. Kotakoski2,4 ,2,3 O. Lehtinen and 3 U. Kaiser

1,2

1

Department of Applied Physics, Aalto University, Finland Department of Physics, University of Helsinki, Finland 3 Central Facility for Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University, Germany 4 Department of Physics, University of Vienna, Austria 2

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References

GRAPHENE 2013

[1] H-P. Komsa, J. Kotakoski, S. Kurasch, O. Lehtinen, U. Kaiser, and A. V. Krasheninnikov, Phys. Rev. Lett. 109 (2012) 035503.

[2] H-P. Komsa and A. V. Krasheninnikov, J. Phys.

Chem. Lett. 3 (2012) 3652.

[3] H.-P. Komsa and A. V. Krasheninnikov, Phys.

Rev. B (Rapid Comm.) 86 (2012) 241201.

107

By combining first-principles simulations with highresolution transmission electron microscopy experiments, we study the evolution of atomically thin layers of transition metal dichalcogenides (TMDs) under electron irradiation. We show that vacancies produced by the electron beam agglomerate and form line structures, which can be used for engineering materials properties. We also study the radiation hardness of 2D TMD materials [1]. We further show that TMDs can be doped by filling the vacancies with impurity atoms.

We also study the stability and electronic properties of single layers of mixed TMDs, such as MoS2xSe2(1−x), which can be referred to as 2D random alloys [2]. We demonstrate that 2D mixed ternary MoS2/MoSe2/MoTe2 compounds are thermodynamically stable at room temperature, so that such materials can be manufactured by CVD or exfoliation techniques. By applying the effective band theory approach we further study the electronic structure of the mixed ternary 2D TMD compounds and show that the direct gap in these material can continuously be tuned. Using GW first-principles calculations for few-layer and bulk MoS2, we further study [3] the effects of quantum confinement on the electronic structure of this layered material. By solving the Bethe-Salpeter equation, we evaluate the exciton energy in these systems. Our results are in excellent agreement with the available experimental data. Exciton binding energy is found to dramatically increase from 0.1 eV in the bulk to 1.1 eV in the monolayer.

The fundamental band gap increases as well, so that the optical transition energies remain nearly constant.

Oral Oxygen Switching of the Epitaxial Graphene-Metal Interaction 1

Paolo Lacovig

Elettra-Sincrotrone Trieste, S.S. 14 Km 163.5, 34149 Trieste, Italy CNR-Institute for Complex Systems, Via Fosso del Cavaliere 100, 00133 Roma, Italy Department of Physics and Astronomy, Interdisciplinary Nanoscience Center, Aarhus University, 8000 Aarhus C, Denmark 4 Physics Department and CENMAT, University of Trieste, Via Valerio 2, 34127 Trieste, Italy and IOM-CNR Laboratorio TASC, Area Science Park, S.S.14 Km 163.5, 34149 Trieste, Italy.

1

R. Larciprete2, S. Ulstrup3 M. Dalmiglio1, M. Bianchi3 F. Mazzola3, L. Hornekær3 F. Orlando4, A. Baraldi4 P. Hofmann3 and S. Lizzit1

2 3

108

The mass production of graphene (GR) based electronic devices requires the synthesis of high quality, i.e. with low defects concentration, and large area GR layers. Among the different methods that can be used for GR preparation, epitaxial growth on transition metal surfaces is one of the most promising techniques to achieve high quality GR layers. The interaction with the substrate, however, is the major drawback of epitaxial GR [1].

In some cases, e.g. GR layers grown on Ru(0001), Rh(111) or Re(0001), this interaction can be sufficiently strong to prevent the typical electronic properties of GR from being established. On the other hand, a very weak interaction, e.g. GR on Pt(111), leads to the formation of GR domains with different orientations.

GR/Ir(111) is a representative example of a weakly bound interface: GR-like electronic properties are observed but the moiré pattern due to the lattice incommensurability between GR and its substrate gives rise to replica bands and minigaps close to the Fermi level. It appears thus difficult to achieve a weak interaction with high structural quality at the same time. A possible solution is the epitaxial growth of GR on a sufficiently interacting substrate, such as Ir(111), and the subsequent decoupling by the intercalation of metals, silicon, fluorine or hydrogen in order to restore, at least partly, the pristine linear band dispersion.

Oxygen intercalation appears as a viable route to decouple GR/metal interfaces, but so far intercalation has been demonstrated only for incomplete monolayers or islands [2]. Here, using high-resolution fast x-ray photoemission spectroscopy (XPS) with synchrotron radiation, we show that oxygen intercalation is achieved on an extended layer of epitaxial GR on Ir(111), which results in the “lifting” of the GR layer and in its

paolo.lacovig@elettra.trieste.it

decoupling from the metal substrate [3]. Below GR oxygen adsorption on the substrate proceeds as on clean Ir(111), the main difference being a slightly higher oxygen coverage. Upon lifting, the C 1s signal shows a downshift in binding energy, due to the charge transfer from GR to the electronegative oxygen. Moreover, the characteristic spectral signatures of the GR-substrate interaction in the valence band are removed, and the spectrum of strongly hole-doped, quasi free-standing GR with a linear π-band dispersion is observed. Temperature programmed fast-XPS measurements pointed out that abrupt oxygen deintercalation with a slight carbon etching occurs around T=600 K. After deintercalation, GR restores its interaction with the Ir(111) substrate.

Additional intercalation/deintercalation cycles readily occur at lower oxygen pressure and temperature, consistently with an increasingly defective lattice.

Our findings demonstrate that oxygen intercalation is an efficient method for fully decoupling an extended layer of GR from a metal substrate. They pave the way for the fundamental research on GR, where extended, ordered layers of free-standing GR are important and, due to the stability of the intercalated system in a wide temperature range, also for the advancement of next-generation GR-based electronics.

References [1] E. Voloshina, and Y. Dedkov, Phys. Chem.

Chem. Phys. 14 (2012) 13502.

[2] P. Sutter, J.T. Sadowski, and E.A. Sutter, J. Am .

Chem. Soc. 132 (2010) 8175.

[3] R. Larciprete et al., ACS Nano 6 (2012) 9551.

Highlighted in Nat. Mater. 12 (2013) 3.

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Oral High-Magnetic-Field Conductivity of Chemically Functionalized Graphene: Electron-Hole Symmetry Breaking in the Quantum Hall regime

Nicolas Leconte F. Ortmann A. Cresti J. â&#x20AC;&#x201C; C. Charlier and S. Roche nicolas.leconte@uclouvain.be

UniversitĂŠcatholique de Louvain (UCL), Institute of Condensed Matter and Nanoscience (IMCN), NAPS, Chemin des ĂŠtoiles 8, 1348 Louvain la Neuve, Belgium

[1] N. Leconte, F. Ortmann, A. Cresti, J.-C. Charlier, and S. Roche, submitted to Nano Letters (2013).

[2] N. Leconte; A. Lherbier, F. Varchon, P. Ordejon, S. Roche, and J.-C. Charlier, Phys.

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Figures

GRAPHENE 2013

References

Rev. B 84 (2011) 235420; N. Leconte, J. Moser, P. Ordejon, H.H. Tao, A. Lherbier, A. Bachtold, F. Alsina, C.M.S. Torres, J.-C. Charlier, and S. Roche, ACS Nano 4 (2010) 4033.

[3] H. Ishii, F. Triozon, N. Koboyashi, K. Hirose, and S. Roche, C.-R. Physique 10 (2009) 283.

[4] D. Soriano, N. Leconte, P. Ordejon, J.-C. Charlier, J.J. Palacios, and S. Roche Phys. Rev. Lett. 107 (2011) 016602; N. Leconte, D. Soriano, S. Roche, P. Ordejon, J.-C. Charlier, and J.J. Palacios, ACS Nano 5 (2011) 3987.

109

In this work [1], we predict a strong electron-hole asymmetry in the Quantum Hall regime in graphene, due to its functionalization by low concentration of oxygen impurities in epoxy position. The scattering potential induced by these impurities is modeled by tight-binding parameters extracted from ab initio calculations [2], which, in turn, are used inside an efficient real space order N method [3] to calculate the dissipative conductivity [4] under high field. Various transport regimes are observed by varying the impurity concentrations from 0.5 to 4.4% and magnetic fields ranging from 1 to 80 Tesla, thus evidencing the complexity of the metal-insulator transition in disordered graphene under high magnetic fields. For lowest concentration of defects (0.5 to 1%), the electronic charge carriers feel substantial localization effects without any Landau levels developing in the spectrum. In contrast, the hole spectrum maintains the anomalous Quantum Hall state with associated Landau levels. Moreover, the conductivity exhibits a double-peak structure, which is associated to magnetic field-induced impurity bound states. The length-dependent conductivity proves the formation of mobility edges separating extended states from localized ones. Increasing even further the impurity concentration (up to 4.4%), we observe a complete disappearance of the quantum Hall effect in oxidized graphene, even for highest magnetic fields.

Invited 1

Graphene Electrodes for Flexible Organic Electronics

Tae-Woo Lee 1 2 T. - H. Han , Y. Lee 1 2 S. - H. Woo , S. - H. Bae Y. - H. Kim1, H. - B. Kim1 1 H. - K. Seo and 2 J. - H. Ahn

1

Department of Materials Science and Engineering, San 31, Hyo-ja Dong, Nam-gu, Pohang, Gyungbuk 790-784, Republic of Korea 2 2SKKU Advanced Institute of Nanotechnology (SAINT), Center for Human Interface Nano Technology (HINT) and School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do 440-746, Republic of Korea

110

Graphene films have a strong potential to replace indium tin oxide anodes in various organic electronic devices such as organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs) and organic thin-film transistors (OTFTs) to date.

Most of all, in OLEDs device, however, the luminous efficiency with graphene anodes has been limited by a lack of efficient methods to improve the low work function and reduce the sheet resistance of graphene films to the levels required for electrodes. Here, we fabricate flexible OLEDs by modifying the graphene anode to have a high work function and low sheet resistance, and thus achieve extremely high luminous power efficiencies (37.2 lm/W in fluorescent OLEDs, 102.7 lm/W in phosphorescent OLEDs), which are significantly higher than those of optimized devices with an indium tin oxide anode (24.1 lm/W in fluorescent OLEDs, 85.6 lm/W in phosphorescent OLEDs). We also fabricate flexible white OLED lighting devices using the graphene anode. These remarkable device efficiencies increase the feasibility of using graphene anodes to make extremely high-performance flexible organic optoelectronic devices by overcoming the major drawbacks (low work function and trap formation due to diffusion of indium and tin) of conventional ITO anodes. These results demonstrate the great potential of graphene anodes for use in a wide variety of highperformance flexible organic optoelectronics such as flexible, stretchable full-colour displays and solid-state lighting. In addition to the OLED application, we will demonstrate OPVs and OTFTs using graphene electrodes.

twlee@postech.ac.kr

References [1] T.-H. Han, Y. Lee, M.-R. Choi, S.-H. Woo, S.-H. Bae, B. H. Hong, J.-H. Ahn and T.-W. Lee, Nature Photon. 6 (2012), 105-110.

Figures

Figure 1: Flexible OLEDs using graphene anode. (a) Optical images of light emission from a flexible green OLED with a four-layered graphene anode doped with HNO3 (b) Performance of phosphorescent OLEDs with four-layered graphene and ITO anodes.

ImagineNano2013

Invited Grain Boundaries in Graphene: Control and Observations

Young Hee Lee 3 G. H. Han 1 D. L. Duong Q. H. Ta1 1 V. L. Nguyen

1,2

1

Center of Integrated Nanostructured Physics, Department of Energy Scicences, Sungkyunkwan University, Suwon, Korea.

2 Department of Physics, Sungkyunkwan University, Suwon, Korea 3 Department of Physics and Astronomy,University of Pennsylvania, United States.

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high temperature annealing gives the best properties of graphene, In the last part of this presentation, we will introduce a method to control number layers of graphene and their interaction in growth process using atmosphere chemical vapor deposition. The key control is the ratio of CH4 and H2 in the chamber. Two different growth modes were observed: i) Stranski–Krastanov in which a full monolayer of graphene is firstly formed following by multilayer islands on the top of monolayer, ii) Volmer–Weber (island) in which multilayer graphene islands are growth simultaneously. The later growth mode shows strong interactions while the former shows random stacking order with weak and strong interactions between layers. These are confirmed by Raman spectroscopy and TEM measurements. The uniform and large scale synthesis of strong interaction graphene layers promises a potential application for bilayer graphene where the gap can be opened up to 0.35 eV by electric field.

[1] Gang Hee Han, Fethullah Güneş, Jung Jun Bae, Eun Sung Kim, Seung Jin Chae, Hyeon-Jin Shin, Jae-Young Choi, Didier Pribat and Young Hee Lee, 'Influence of Copper Morphology in Forming Nucleation Seeds for Graphene Growth', Nano Letters, 11 (2011), 4144-4148.

[2] Dinh Loc Duong, Gang Hee Han, Seung Mi Lee, Fethullah Gunes, Eun Sung Kim, Sung Tae Kim, Heetae Kim, Quang Huy Ta, Kang Pyo So, Seok Jun Yoon, Seung Jin Chae, Young Woo Jo, Min Ho Park, Sang Hoon Chae, Seong Chu Lim, Jae Young Choi and

GRAPHENE 2013

References

111

The ability of synthesis graphene as large scale gives rise to use graphene as many applications e.g transparent flexible conducting electrode, transistors, optoelectronic… However, the quality of graphene is governed by many impacts from their intrinsic defects (grain boundaries, point defects, wrinkles, ripples…) to substrate interaction (charge puddles, lattice mismatch, interface interaction…). In this presentation, we will focus on the mechanism to form graphene grain boundaries (GGBs) that were observed both in SEM and Confocal Raman mapping. We observed that the graphene film is formed by stitching different graphene flakes. By oxidation of graphene flakes, GGBs inside individual flake are also observed by confocal raman mapping.

The new method using optical microscopy is also introduced to probing GGBs. This imaging technique was realized by selectively oxidizing the underlying copper foil through the graphene grain boundaries using OH radicals generated by ultraviolet light irradiation under moisture-rich ambient conditions. This approach permitted the graphene grain boundaries that are distinguishable from the copper grain boundaries to be visualized using optical microscopy. We found that the sheet resistance of large-area graphene decreased as the extracted graphene grain sizes increased, but no strong correlation with the grain size of the copper was revealed, in contrast to previous reports. To control GGBs or graphene grain size, polishing and annealing copper foil at high temperature are performed to reduce number of nucleation seeds. Different polishing methods will be compared and the effects of annealing time and temperature will also be presented. Combination of polishing and

leeyoung@skku.edu

Young Hee Lee,'Probing graphene grain boundaries with optical microscopy', Nature, 490 (2012), 235-239.

[3] Quang Huy Ta et. al. Unpublished.

Figures

Figure 1: Evolution of different patterns on graphene flakes under different oxidation time [1].

112

Figure 2: Observation of graphene grain boundaries by optical microscopy and their effect to sheet resistance [2].

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Oral Graphene Hot Electron Transistors

1,3

Max C. Lemme 1 2 S. Vaziri , G. Lupina 1 1 A. D. Smith , M. Östling J. Dabrowski2, G. Lippert2 2 and W. Mehr

1

KTH Royal Institute of Technology, School of Information and Communication Technology, Isafjordsgatan 22, 16440 Kista, Sweden, 2 IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany 3 University of Siegen, Hölderlinstr. 3, 57076 Siegen, Germany

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of the base-collector insulator. Measured transfer characteristics of the GBTs show ON/OFF current ratios exceeding 104 (Figure 3a, [11]). Theoretical calculations predict that ON/OFF current ratios of over five orders of magnitude and operation up to the THz frequency range can be obtained with GBTs [6] (Figure 3b). Temperature dependent measurements will be discussed in the talk and confirm the predicted tunneling mechanism.

Acknowledgements: Support from the European Commission through a STREP project (GRADE, No. 317839), an ERC Advanced Investigator Grant (OSIRIS, No. 228229) and an ERC Starting Grant (InteGraDe, No. 307311) as well as the German Research Foundation (DFG, LE 2440/1-1) is gratefully acknowledged.

[1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, "Electric Field Effect in Atomically Thin Carbon Films," Science, vol.

306, pp. 666-669, October 22, 2004 2004.

[2] M. C. Lemme, T. J. Echtermeyer, M. Baus, and H. Kurz, "A Graphene Field-Effect Device," IEEE Electron Device Letters, vol. 28, pp. 282-284, 2007.

[3] L. Britnell, R. V. Gorbachev, R. Jalil, B. D. Belle, F. Schedin, A. Mishchenko, T. Georgiou, M. I. Katsnelson, L. Eaves, S. V. Morozov, N. M. R. Peres, J. Leist, A. K. Geim, K. S. Novoselov, and L. A. Ponomarenko, "Field-Effect Tunneling Transistor Based on Vertical Graphene Heterostructures," Science, vol. 335, pp. 947950, February 24, 2012 2012.

GRAPHENE 2013

References

113

Graphene has been investigated intensely as a next-generation electronic material since the presence of the field effect was reported in 2004 [1]. The absence of a band gap and the resulting high off-state leakage currents prohibit graphene as the channel material in field effect transistors (FETs) for logic applications [2]. Several alternative graphene device concepts have been proposed that rely on quantum mechanical tunneling. These include graphene / hexagonal boron nitride superlattices [3] or (gated) graphene / semiconductor Schottky barriers [4, 5]. Along these lines, we recently proposed a Graphene Base Transistor (GBT) [6], a hot electron transistor (HET) [7-9] with a base contact made of graphene that can potentially deliver superior DC and RF performance [6] (Figure 1). HETs with metallic bases are limited by two mechanisms: carrier scattering and “self-bias crowding” (in-plane voltage drop) in the base material. Optimization becomes a trade-off, since thinning the metal-base reduces scattering, but increases the metal-base resistance and the self-bias crowding [7].

Graphene is thus the ideal material for HET bases due to its ultimate thinness and high conductivity.

We experimentally demonstrate DC functionality of graphene-based hot electron transistors, which we call Graphene Base Transistors (GBT, Figure 1).

The fabrication scheme is potentially compatible with silicon technology and can be carried out at the wafer scale with standard silicon technology [10]. The state of the GBTs can be switched by a potential applied to the transistor base, which is made of graphene. Figure 2 shows schematic band structures for an unbiased device (a) and a biased device in the off- (b) and in the on-state (c). In the on-state, Fowler-Nordheim tunneling leads to the injection of hot carriers into the conduction band

max.lemme@uni-siegen.de

114

[4] S. Tongay, M. Lemaitre, T. Schumann, K. Berke, B. R. Appleton, B. Gila, and A. F. Hebard, "Graphene/GaN Schottky diodes: Stability at elevated temperatures," Applied Physics Letters, vol. 99, pp. 102102-3, 2011.

[5] H. Yang, J. Heo, S. Park, H. J. Song, D. H. Seo, K.-E. Byun, P. Kim, I. Yoo, H.-J. Chung, and K. Kim, "Graphene Barristor, a Triode Device with a Gate-Controlled Schottky Barrier," Science, vol. 336, pp. 1140-1143, June 1, 2012 2012.

[6] ] W. Mehr, J. C. Scheytt, J. Dabrowski, G. Lippert, Y.-H. Xie, M. C. Lemme, M. Ostling, and G. Lupina, "Vertical Transistor with a Graphene Base," IEEE Electron Device Letters, vol. 33, pp. 691-693, 2012.

[7] C. A. Mead, "Operation of Tunnel-Emission Devices," Journal of Applied Physics, vol. 32, pp. 646-652, 1961.

[8] M. Heiblum, "Tunneling hot electron transfer amplifiers (theta): Amplifiers operating up to the infrared," Solid-State Electronics, vol. 24, pp. 343-366, 1981.

[9] T. Yajima, Y. Hikita, and H. Y. Hwang, "A heteroepitaxial perovskite metal-base transistor," Nature Materials, vol. 10, pp. 198201, 2011.

[10] S. Vaziri, G. Lupina, A. Paussa, A. D. Smith, C. Henkel, G. Lippert, J. Dabrowski, W. Mehr, M. Ă&#x2013;stling, and M. C. Lemme, "A Manufacturable Process Integration Approach for Graphene Devices," accepted for publication: Solid State Electronics, 2013.

[11] S. Vaziri, G. Lupina, C. Henkel, A. D. Smith, M. Ă&#x2013;stling, J. Dabrowski, G. Lippert, W. Mehr, and M. C. Lemme, "A Graphene-based Hot Electron Transistor," http://arxiv.org/abs/1211.2949, 2012.

Figures

Figure 1: a) Schematic and b) optical micrograph (top view) of a graphene hot electron transistor (HET).

Figure 2: Schematic band structure of a graphene HET. a) unbiased, b) Off-state with finite collector bias and no base bias and c) Onstate with finite collector Vc and base voltage Vb (Vc>Vb).

Figure 3: a) Measured transfer characteristics of two graphene HETs with an On-Off ratio of 103 and 5x104. b) Simulated cutoff frequency for a graphene HET with optimized dielectric barriers [6].

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Invited Interesting Properties of Strained or Defective Graphene

Kian Ping Loh

Department of Chemistry and Graphene Research Centre, 3 Science Drive 3, Singapore, Singapore 117543

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References

GRAPHENE 2013

[1] Jiong Lu, A. H. Castro Neto and Kian Ping Loh* Transforming Graphene Moire Blisters to Geometric Nanobubbles Nature Communications 8; 3: (2012) 823.

[2] Chen Liang Su and Kian Ping Loh* et. al., Probing the Catalytic Activity of Graphene Oxide and its origin, Nature Communications, 3, (2012) 1298.

[3] Candy Su, Kian Ping Loh et. al.* A hydrothermal Anvil made of Graphene nanobubbles on diamond Nature Communications (2013), 10.1038/ncomms 2579.

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Most people think of graphene as a flat membrane and the quality of physics observation depends on the flatness of it. However defective or strained graphene can present interesting properties, especially to a chemist. For example, generating pores or voids in graphene, oxidizing and disrupting the conjugation, as in the case of nanoporous graphene oxide, can generate a material that is catalytically active – what the chemists called “carbocatalyst”. Nanoporous graphene oxide can mediate a wide range of chemical transformation. We have managed to identify a simple chemical treatment to introduce porosity and tune the acidity of Graphene Oxide (GO). This is a potentially important area for industrial applications [1].

Generating strain textures on graphene allows the engineering of new energy landscape. The Dirac electrons in graphene couples to strain via pseudomagnetic field, creating an electrodynamics that is controlled by the geometry of the strain.

Using the graphene Moiré superlattice, geometrically precise nanobubbles can be generated that show pseudomagnetic field in the hundreds of Telsa [2]. We discuss the chemistry of how such strain texture can be created by controlling sub-surface defects on the metal substrate. Nanobubbles on graphene can also be created when graphene is transferred onto diamond. Very robust interfacial bonding between diamond and graphene allows a hydrothermal anvil to be created at the interface. Superheated water trapped at the interface becomes corrosive at high temperature and pressure and can etch diamond [3].

Oral Near-band edge optical properties of exfoliated h-BN layers 1

LEM, ONERA-CNRS, 29 avenue de la Division Leclerc, Châtillon, France GEMaC, Université Versailles St Quentin – CNRS, 45 avenue des Etats Unis, Versailles, France 3 Group ‘Nanophysique et Semi-conducteurs’, CEA/INAC –CNRS-UJF, 17 rue des Martyrs, Grenoble, France 4 LPA, ENS-CNRS, 24 rue Lhomond, Paris, France

Annick Loiseau 1,2 J. Loayza 2 J. Barjon A. Pierret1,3 4 A. Betz 4 B. Plaçais and 1 F. Ducastelle

1

2

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Hexagonal boron nitride is a wide band gap semiconductor (~ 6.5 eV), which meets a growing interest for graphene engineering [1]. In particular electron mobility of graphene is shown to be preserved when it is supported by a h-BN film, in particular when mechanically exfoliated from h-BN crystallites. Nevertheless the use of BN sheets grown by CVD techniques remains an open issue as this material might present structural defects degrading graphene properties. It is therefore highly desirable to better know optical and electronic properties of thin BN layers, in correlation with their structural properties and the impact of the underlying BN layer on electronic properties of graphene.

Until recently, these properties were poorly known due to both the scarcity of crystals and suitable investigation tools. This situation has changed thanks, first, to the development of dedicated photoluminescence (PL) and cathodoluminescence (CL) experiments running at 4K and adapted to the detection in the far UV range [2, 3, 4], and second to the availability of high quality single crystals [5].

HBN has been shown to display original optical properties, governed by strong Frenkel-type excitonic effects, in the 5.5 – 6 eV energy range [2, 3, 6]. The existence of these high energy excitons has been confirmed by reliable theoretical calculations [7, 8]. Furthermore, since excitons are highly sensitive to their environment, they are easily trapped on defects such as dislocations, as revealed by combined cathodoluminescence measurements and transmission electron microscopy (TEM) observations [4].

In this work, we examine how these properties can be further exploited for the characterization of BN layers to be used as support for graphene. We carry out optical and structural characterizations of

annick.loiseau@onera.fr

this material by combining CL at 4K in the UV range (up to 6eV) and electron microscopy. Thin layers have been obtained by mechanically exfoliating small crystallites. Exfoliated flakes were reported on SiO2 substrates for AFM thickness measurements, as described in [9].

Results are illustrated in Figure 1 and detailed in [10]. As for the bulk, excitonic emission consists of two series of lines called S and D. In the bulk, S excitons have been found to be self-trapped, due to a Jahn- Teller effect [3]. Emission related to D lines is found to be localized on defects such as grain boundaries, whereas in defect free areas, D lines completely vanish and only S lines are observed. D/S ratio can therefore be used as a qualification parameter of the defect densities present in the layers. Furthermore, when film thickness stands below 5-6 atomic layers, energies of S and D lines are shifted towards higher energies. This shift can be due to a perturbation in the strain environment of the exciton induced by the reduction in thickness or by the exciton confinement. Ongoing investigation of single and double atomic layers will permit to further investigate this effect and understand its exact origin. This shift in energy could be used for the determination of the number of layers, complementary to AFM measuremen.

References [1] C.R. Dean et al., Nature Nanotechnology 5 (2010) 722.

[2] P. Jaffrennou et al., Phys. Rev. B 77 (2008) 235422.

[3] K. Watanabe et al., Phys. Rev. B 79 (2009) 193104.

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[4] P. Jaffrennou et al., J. Appl. Phys. 102 (2007) 116102.

[5] Y. Kubota et al.. Science 317 (2007) 932.

[6] L. Museur et al., Phys. Stat. Sol. rrl 5 (2011) 414.

[7] B. Arnaud et al., Phys. Rev. Lett. 96 (2006) 026402.

[8] C.-H. Park et al., Phys. Rev Lett. 96 (2006) 126105.

[9] G. F. Schneider et al., Nano. Lett. 10 (2010) 1912.

[10] J. Loayza et al., Nanoletters, submitted (2013).

Figures

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Figure 1: Left: AFM image of an exfoliated h-BN flake. Thickness measurement by AFM along the cross section indicated by the dashed green line, indicates that the flake is composed up to 9 atomic sheets. Right: CL spectrum recorded at 4K on the area of the flake indicated by the red square. The near band edge emission is composed of S and D lines.

Oral Ultra-Clean Freestanding Graphene by Pt-metal catalysis

Jean-Nicolas Longchamp C. Escher and H. - W. Fink

Physics Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland

longchamp@physik.uzh.ch

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The physical and electronic properties of grapheme [1, 2] depend to a large extent on its defect-free structure and its cleanliness. Scattering of transport electrons at impurities is one of the major drawbacks in view of employing graphene in electronic devices [3, 5]. Furthermore, when using graphene as a substrate in electron microscopy, the presence of residues is obstructive because the latter are often of the same size as the object under study [6] While the growth of defect-free singlelayer graphene by means of chemical vapor deposition (CVD) is nowadays a routine procedure [7, 8], easily accessible and reliable techniques to transfer graphene to different substrates in a clean manner are still lacking. The common technique for the transfer of the layers grown by means of CVD on a metallic substrate (usually nickel or copper) onto an arbitrary substrate requires a polymer support layer, usually polymethyl methacrylate (PMMA), spread or spin-coated over the grapheme [5, 9, 10] The subsequent removal of this approximately 100 nm thick PMMA layer is a challenge, and extensive efforts have been undertaken in the past few years to establish a reliable technique to retrieve pristine graphene without PMMA residues [3–5, 11–14]. Well known chemical etchants for PMMA are acetone and chloroform (15). Unfortunately, wet chemical treatment of the polymer leads to contaminated graphene layers with excessive residues. Thermal annealing at temperatures in the range of 300°C – 400°C in vacuum [12, 15] or in an Ar/H2 atmosphere [15] appears to promote the cleaning process. However, besides the fact that these techniques are not easily available, they do not lead to ultra-clean freestanding graphene. We have discovered a method for preparing ultraclean freestanding grapheme using the catalytic

properties of platinum metals. Complete catalytic removal of polymer residues only requires annealing in air at a temperature between 175°C and 350°C. After the catalytic removal of the PMMA layer, the cleanliness of the freestanding graphene sheets is characterized in the low-energy electron point source microscope. In its holographic setup inspired by the original idea of Gabor [16], a sharp (111)-oriented tungsten tip acts as source of a divergent beam of highly coherent electrons [17].

The electron emitter can be brought as close as 200 nm to the grapheme sample with the help of a 3-axis piezo-manipulator. Part of the electron wave impinging onto the sample is elastically scattered and forms the object wave, while the unscattered part of the wave represents the reference wave [18] At a distant detector, the interference pattern between the object wave and the reference wave – the hologram – is recorded.

The magnification of the microscopic record is given by the ratio of detector-tip-distance to sample-tip-distance and can be as high as one million. Figure 1(a) displays a hologram of a freestanding ultra-clean graphene layer covering a 500 nm diameter hole recorded with our lowenergy electron point source microscope at a kinetic electron energy of 61 eV and a total electron current of 50 nA. Clean freestanding graphene is almost transparent even for lowenergy electrons [19, 20] and the presence of graphene can only be confirmed by observing individual adsorbates, possibly from the gas phase, sticking to the monolayer. For comparison, figure 1(b) shows an image of freestanding graphene (70eV, 500nA), where the polymer layer was removed in the common manner by dissolving it in acetone. The resulting graphene layer is still

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[1] K. S. Novoselov et al., Proceedings of the National Academy of Sciences of the United States of America 102, 10451–10453 (2005).

[2] A. K. Geim, K. S. Novoselov, Nature Materials 6, 183–191 (2007).

[3] M. Ishigami, J. H. Chen, W. G. Cullen, M. S. Fuhrer, E. D. Williams, Nano letters 7, 1643–8 (2007).

[4] Y. Dan, Y. Lu, N. J. Kybert, Z. Luo, A. T. C. Johnson, Nano letters 9, 1472–5 (2009).

[5] A. Reina et al., Journal of Physical Chemistry C 112, 17741–17744 (2008).

[6] R. R. Nair et al., Applied Physics Letters 97, 153102 (2010).

[7] X. Li et al., Science (New York, N.Y.) 324, 1312– 4 (2009).

[8] Y. Lee et al., Nano letters 10, 490–3 (2010).

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Figures

Figure 1: (a) Low-energy electron hologram of ultra-clean freestanding graphene prepared by our patented method, (b) electron transmission after the removal of the PMMA layer with acetone, (c) TEM image of a hole of 500 nm in diameter entirely covered with ultra-clean freestanding graphene, (d) high magnification image of the region marked by a red square in (c).

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References

[9] X. Li et al., Nano letters 9, 4359–63 (2009).

[10] J. W. Suk et al., ACS nano 5, 6916–24 (2011).

[11] C. R. Dean et al., Nature nanotechnology 5, 722–6 (2010).

[12] A. Nourbakhsh et al., The Journal of Physical Chemistry C 114, 6894–6900 (2010).

[13] Z. H. Ni et al., Journal of Raman Spectroscopy 41, 479–483 (2009).

[14] J.-H. Chen et al., Nature Physics 4, 377–381 (2008).

[15] Z. Cheng et al., Nano letters 11, 767–71 (2011).

[16] D. Gabor, Nature 161, 777–778 (1948).

[17] H. W. Fink, Physica Scripta 38, 260–263 (1988).

[18] H.-W. Fink, W. Stocker, H. Schmid, Physical Review Letters 65, 1204–1206 (1990).

[19] J. Y. Mutus et al., New Journal of Physics 13, 63011 (2011).

[20] J.-N. Longchamp, T. Latychevskaia, C. Escher, H.-W. Fink, Applied Physics Letters 101, 113117 (2012).

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polluted and almost opaque, even when imaged with a tenfold increased electron current, and the presence of PMMA residues is evident. Similar results to those shown in figure 1(a) were also obtained with Pd as catalyst. Attempts to use other metals, such as gold, for cleaning graphene failed.

Low-energy electron microscopy investigations revealed, in these cases, either empty holes where the graphene broke, or opaque holes where the graphene was heavily contaminated. The cleanliness of the graphene sheet prepared as explained above was also verified by TEM investigations at 80 keV. Figure 1(c) shows a hole of 500 nm in diameter entirely covered by an ultra-clean single-layer graphene sheet. The presence of graphene is only detected at high magnification were the unit cell becomes apparent (Figure 1(d)). Specialists in TEM studies on graphene have confirmed that such wide areas of atomically clean freestanding graphene have never been observed before.

Here, we will describe in detail the preparation process for obtaining ultra-clean freestanding grapheme by Pt-metal catalysis. The presentation of low-energy electron holography and TEM investigations will demonstrate that areas of ultraclean freestanding graphene as large as 2 square microns can now routinely be prepared. These findings will have important impacts for the application of graphene in the field of electron microscopy and possibly in electronics.

Invited Continuum Model of the Twisted Bilayer

1

J. M. B. Lopes dos Santos 1 N. M. R. Peres and 1 A. H. Castro Neto

jlsantos@fc.up.pt 1

CFP and Departamento de Física, Facultade de Ciências, Universidade do Porto 4169-007 Porto, Portugal

The electronic structure of the twisted bilayer was considered [1] in the context of a continuum description of the two layers, coupled by a spatially modulated hopping. The model’s predictions were subsequently confirmed by experiments [2, 3], including a scanning tunneling spectroscopy finding of two low energy Van-Hove peaks in the density of states [4], and by band structure calculations[5, 6].

We discuss the extension of the model in several directions: the two families of commensurate structures discovered by Mele [7], will be characterized by elementary geometrical arguments; it will be shown that it is possible to calculate analytically all Fourier components of the hopping amplitudes for any kind of commensurate structure with large period. This allows calculations with the continuum model to be extended beyond the perturbative regime in the interlayer coupling, to address the electronic structure and local density of states in the very small angle limit [8]. A physically transparent explanation of carrier localization in AA stacked regions emerges [9], which gives a good account of the “magic angles” (values of the twist angle with zero fermi velocity) found by Bistritzer and MacDonald [10].

[6] G. de Laissardiere, et. al, Nano Letters 10,804 (2010).

[7] E. J. Mele, Phys. Rev. B 81, 161405 (2010).

[8] J. M. B. Lopes dos Santos, N. M. R. Peres and A H Castro Neto, Phys. Rev. B 86, 155449 (2012).

[9] ] G. Trambly de Laissardiere, D. Mayou, and L. Magaud, Phys. Rev. B 86, 125413 (2012).

[10] R. Bistritzer and A. H. MacDonald, Proc. Natl.

Acad. Sci. USA 108, 12233 (2011).

References

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[1] J. M. B. Lopes dos Santos, N. M. R. Peres and A H Castro Neto, Phys. Rev. Lett. 99, 256802, (2007).

[2] Z. Ni, et. al., Phys. Rev. B 77, 235403, 2008.

[3] A. Luican, et. al, Phys. Rev. Lett. 106, 126802 (2011).

[4] G. Li, et. al, Nature Physics 6, 109 (2010).

[5] S. Shallcross, et. al, Phys. Rev. B 81, 165105 (2010).

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Oral Electron spin relaxation and decoherence by magnetic defects in graphene

Mark B. Lundeberg* R. Yang J. Renard and J. A. Folk

mark.lundeberg@icfo.es Department of Physics, University of British Columbia, Vancouver, British Columbia, V6T1Z4, Canada *now at ICFO - The Institute of Photonic Sciences, Castelldefels (Barcelona) 08860 Spain

Evidence for electron spin relaxation in graphene by paramagnetic defects is presented, based on transport measurements of electron coherence lifetimes in an in-plane magnetic field. This mechanism provides an explanation for past observations of significant spin relaxation rates espite the theoretical expectations of negligible spin-orbit and hyperfine interactions.

References [1] M. B. Lundeberg, R. Yang, J. Renard, and J. A. Folk, Phys. Rev. Lett. (accepted) / arxiv:1211.1417.

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Figure 1: Measured electron decoherence rate in low temperature graphene. The reduced decoherence in the presence of a high inplane magnetic field (six tesla: filled circles) compared to zero magnetic field (open circles) indicates the quenching of magnetic defects.

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Oral Laurence Magaud 2 G.Trambly de Laissardière 1 J.F.Jobidon D.Mayou1 1 P.Mallet and 1 J.-Y.Veuillen

1

laurence.magaud@grenoble.cnrs.fr

2

Institut Néel, CNRS&UJF, Grenoble FRANCE LPTM, Université de Cergy, Cergy, FRANCE

Graphene bilayers, with either AA or AB (Bernal) stacking have been known for years [1] but surprisingly, graphenic systems offer a much wider range of configurations. Indeed it has been shown from experiments that graphene planes can be rotated on some substrates – e.g. C face of SiC [2], graphite [3], Ni[4]- with an angle between successive layers that ranges from 0° -AA stackingto 60° -AB stacking-. These rotations create in moiré patterns that are observed on STM images [2]. Here we show that these rotated (twisted) bilayers differ both from graphene and graphite and that their electronic structure is governed by the rotation angle. While a large rotation angle (close to 30°) results in two decoupled graphene layers [5-12], carriers in a twisted graphene bilayer evolve from Dirac fermions to strongly localized electrons or holes when the rotation angle is decreased toward very small angles (or increased toward 60°, the system is symmetric with respect to =30°, Figure 1).

We have investigated the electronic structure of graphene bilayers as a function of  by a coupled ab initio – tight binding (TB) approach and we will compare our theoretical results to experimental data when available. When decreases, the velocity of the bilayer is first reduced with respect to the velocity of the monolayer and follows the law proposed first by Lopes dos Santos et al [8,9] (blue line in figure 1). At the intersection between two Dirac cones originating from two different layers, interaction between the states opens gaps and saddle points appear (Figure 2). At 2D such saddle points give rise to van Hove singularities (named E+ and E- in Figure 2) characterized by sharp peaks in the density of states (DOS). As is brought closer to 0°, the two van Hove singularities fall closer and closer to the Dirac point and

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Graphene Stacks: a small rotation makes the difference

eventually merge for  close to 2°. While velocity renormalization remains controversial [13], van Hove singularities have indeed been observed in different systems: graphene on SiC [14], on Ni[4] confirming the theoretical predictions.

Here we will focus on the very small angle limit that have not yet been probed experimentally.

When the two van Hove singularities merge, the DOS shows a sharp peak at the Dirac point. States belonging to this peak are localized in the AA region of the moiré pattern. When the angle is further reduced, velocity alternatively increases and decreases (insert Figure 2) and it is equal to zero for magic angles n that follow a 1/n law [12,7]. We will show that this behavior comes from the confinement of the carriers in the AA regions of the moiré and that beyond sharp peak at the Dirac point, the confinement also leads to the appearance of sharp peaks for energies different from zero.

Eventually robustness of the theoretical predictions is tested for intermediate rotation angles with respect to different perturbations such as constrain, corrugation, point defects and pecular electronic properties are searched. A parallel with the effect of a superpotential on monolayer graphene will be made.

References [1] S.Latil, L.Henrard, Phys. Rev. Lett 97, 036803 (2007).

[2] F.Varchon, P.Mallet, L.Magaud, J.-Y.Veuillen, Phys. Rev. B 77, 165415 (2008).

[3] G. Li, A. Luican, J. M. B. Lopez dos Santos, A. H. Castro Neto, A. Reina, J. Kong and E. Andrei, Nat. Phys., 6 (2010) 109.

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[4] A.Luican, G.Li, A.Reina, J.Kong, R.R.Nair, K.S.Novoselov, A.K.Geim, E.Y.Andrei, Phys.

Rev. Lett 106, 126802 (2011).

[5] J. Hass, F.Varchon,J.E.Millan-Otoya, M.Sprinkle, N.Sharma, W.de Heer, C.Berger, P.N.First, L.Magaud, E.H.Conrad, Phys. Rev. Lett. 100, 125504 (2008).

[6] G. Trambly de Laissardière, D. Mayou, and L. Magaud, Nano Lett., 10 (2010) 804.

[7] G. Trambly de Laissardière, D. Mayou, and L. Magaud, Phys. Rev. B, 86 (2012) 125413.

[8] J. M. B. Lopes dos Santos, N. M. R. Peres, and A. H. Castro Neto, Phys. Rev. Lett., 99 (2007) 256802.

[9] J. J. M. B. Lopes dos Santos, N. M. R. Peres, and A. H. Castro Neto, Phys. Rev. B86, 155449 (2012).

[10] E.Suarez Morell, J.D.Correa, P.Vargas, P.Pacheco, Z.Barticevic, Phys. Rev. B82, 121407 ® (2010).

[11] . S Latil et al Phys. Rev. B 76, 201402(R) (2007).

[12] R.Bistritzer, A.H.MacDonald, PNAS 108, 12233 (2011).

[13] J. Hicks et al., Phys. Rev. B 83 (2011) 205403.

[14] I. Brihuega, P. Mallet, H. González-Herrero, G. Trambly de Laissardière, M. M. Ugeda, L. Magaud, J.M. Gómez-Rodríguez, F. Ynduráin, and J.-Y. Veuillen, Phys. Rev. Lett., 109 (2012) 196802.

Figure 2: Van Hove singularities and velocity renormalization. (a) scheme, (b)- left: Band structure of the (6,7) bilayer (red) compared to the free monolayer graphene one (black), (b)-right DOS and van Hove singularities.

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Figure 1: Ratio between the velocities of the bilayer and of the monolayer as a function of the rotation angle. Red crosses: ab initio calculations, black and green dots: TB calculations, blue line: law by Lopes Dos Santos et al. Insert: very small angle behavior. Black dot: TB calculation, yellow line: magic angles by Bistritzer and MacDonalds.

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Invited How to make graphene superconducting

Francesco Mauri

Francesco.Mauri@impmc.jussieu.fr Institut de Min´eralogie et de Physique des Milieux Condens´es Universit´e Pierre et Marie Curie 140 rue de Lourmel, 75015 Paris, France

Graphene represents a physical realization of many fundamental concepts and phenomena in solid state-physics, but in the long list of its remarkable properties a fundamental one is missing, i.e. superconductivity.

Making graphene superconducting would have great impact, as the facile manipulation of this material by nanolytographic techniques would pave the way to nanosquids, one-electron superconducting quantum dots, superconducting transistors and cryogenic solid-state coolers. Here we show how one can create and engineer a superconducting transition by adatoms' doping [1].

Density-functional theory calculations show that the occurrence of superconductivity depends on the adatoms' chosen, in close analogy to the case of graphite-intercalated compounds (GICs).

However, most surprisingly, and contrary to the case of GICs, Li-covered graphene is found to be superconducting at much a higher temperature with respect to Ca-covered grapheme

References

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[1] G. Profeta, M. Calandra, F. Mauri, Nature Physics 8, 131-134 (2012).

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Invited Graphene based platforms for biosensing applications

Nanobioelectronics & Biosensors Group Catalan Institute of Nanoscience and Nanotechnology (ICN2) Campus UAB, Bellaterra (Barcelona), Spain

Arben Merkoรงi E. Morales and L. Pires

arben.merkoci@icn.cat

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Graphene due to its mechanical, electronic, chemical, optical and electrochemical properties, represents the most interesting building block for biosensing technology. The possibility of conjugating graphene with biomolecules has received particular attention with respect to the design of chemical sensors and biosensors. Among the various graphene forms graphene oxide (GO) displays advantageous characteristics as a biosensing platform due to its excellent capabilities for direct wiring with biomolecules, heterogeneous chemical and electronic structure, the possibility to be processed in solution and the availability to be tuned as insulator, semiconductor or semi-metal.

Moreover, GO bears the photoluminescence property with energy transfer donor/acceptor molecules exposed in a planar surface and even can be proposed as a universal highly efficient long-range quencher, which is opening the way to several unprecedented biosensing strategies. The rationale behind the use of the various graphene forms in optical and electrochemical (including reduced graphene) biosensing will be discussed.

Taking advantage of the graphene properties we are developing simple, sensitive, selective and rapid biosensing platforms based on this emerging advantageous material. The developed devices have potential interest for biomedical application, environmental monitoring, safety and security.

Invited New horizons and challenges in the microscopic characterization of 2 -D materials

Jannik Meyer Jannik.Meyer@univie.ac.at

University of Vienna, Physics department Bolzmanngasse 5 1090 Vienna, Austria

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The microscopic characterization of twodimensional materials, and low-dimensional matter in general, poses unique challenges but also opens unique new avenues that are not available with 3-D bulk structures or on the surfaces of 3D crystals. In this talk, I will discuss these aspects in connection with high-resolution electron microscopic studies as well as scanning probe investigations.

The study of nano-carbons and other low-atomic number materials remains a particular challenge for high resolution transmission electron microscopy (HRTEM) owing to their intrinsically low contrast and high susceptibility to radiation damage [1]. However, the recent developments in aberration-corrected electron optics open a route to a atomically-resolved studies of these materials at reduced electron energies [2â&#x20AC;&#x201C;9] below the knock-on threshold of carbon atoms in graphene [10,11]. I will present insights to this class of materials from electron microscopic studies with single-light-atom precision. Static deformations, topological defects, various vacancy configurations, the two-dimensional equivalent of dislocations, grain boundaries and substitutional dopants can be analyzed and exact atomic configurations are obtained.

At the same time, the electron microscope can be used to structure and modify graphene with highest resolution and with a direct feedback [12â&#x20AC;&#x201C; 14]. We analyzed the mechanisms behind beamdriven structural changes and demonstrate how a controlled modification, beyond the ejection of atoms, can be achieved [15]. An electron beam can be used to selectively suppress and enhance bond rotations and atom removal in graphene, which allows to turn graphene into a two-dimensional coherent amorphous membrane composed of sp2-

hybridized carbon atoms [15,16]. In addition, substitutional doping of graphene can be obtained not only via a modified synthesis but also by electron irradiation effects [17]. The graphene substrate may further serve as an extreme thermal test platform, which then provides a means to study physisorbed carbon species under the influence of high temperatures and electron irradiation [18].

Nevertheless, for TEM imaging, beam-induced material modifications remain as a primary concern and limitation [19]. I will show a new approach on how to circumvent the radiation damage problem for imaging of material configurations based on a statistical treatment of large, noisy, low-dose data sets. This can reduce the required dose per area by several orders of magnitude, and will open a route to study beamsensitive configurations that are currently not accessible. It will be of particular importance for TEM studies of low-dimensional materials, where every atom (rather than atomic column) is important for the analysis of the projected structure.

As a complementary tool of atomic-level analysis, scanning probe microscopy and in particular scanning tunneling microscopy (STM) has been extensively used for studying graphene and related materials. Very recently, free-standing membranes of graphene have been explored by STM [20â&#x20AC;&#x201C;22].

In the freestanding case, the deformation of the graphene membrane induced by the STM tip is the predominant effect to the height profiles, meaning that the membrane follows the probe rather than vice versa. I will show initial results from a dualprobe STM setup where a free-standing graphene membrane is probed simultaneously from opposing sides. At the closest point, the two

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[1] F. Banhart, Reports on Progress in Physics 62, 1181 (1999).

[2] J. C. Meyer, C. Kisielowski, R. Erni, M. D. Rossell, M. F. Crommie, and A. Zettl, Nano Letters 8, 3582 (2008).

[3] M. H. Gass, U. Bangert, A. L. Bleloch, P. Wang, R. R. Nair, and a K. Geim, Nature Nanotechnology 3, 676 (2008).

[4] A. Chuvilin, J. C. Meyer, G. Algara-Siller, and U. Kaiser, New Journal of Physics 11, 083019 (2009).

[5] O. L. Krivanek, N. Dellby, M. F. Murfitt, M. F. Chisholm, T. J. Pennycook, K. Suenaga, and V. Nicolosi, Ultramicroscopy 110, 935 (2010).

[6] P. J. F. Harris, Z. Liu, and K. Suenaga, Journal of Physics: Condensed Matter 20, 362201 (2008).

[7] U. Kaiser, J. Biskupek, J. C. Meyer, J. Leschner, L. Lechner, H. Rose, M. Stöger-Pollach, A. N. Khlobystov, P. Hartel, H. Müller, M. Haider, S. Eyhusen, and G. Benner, Ultramicroscopy 111, 1239 (2011).

[8] K. Suenaga, K. Akiyama-Hasegawa, Y. Niimi, H. Kobayashi, M. Nakamura, Z. Liu, Y. Sato, M. Koshino, and S. Iijima, Journal of Electron Microscopy 61, 285 (2012).

[9] J. H. Warner, E. R. Margine, M. Mukai, a. W. Robertson, F. Giustino, and a. I. Kirkland, Science 337, 209 (2012).

[10] A. Zobelli, A. Gloter, C. Ewels, G. Seifert, and C. Colliex, Physical Review B 75, 1 (2007).

[11] J. Meyer, F. Eder, S. Kurasch, V. Skakalova, J. Kotakoski, H. Park, S. Roth, A. Chuvilin, S. Eyhusen, G. Benner, A. Krasheninnikov, and U. Kaiser, Physical Review Letters 108, 196102 (2012).

[12] J. C. Meyer, C. O. Girit, M. F. Crommie, and A. Zettl, Applied Physics Letters 92, 123110 (2008).

[13] M. D. Fischbein and M. Drndic, Applied Physics Letters 93, 113107 (2008).

[14] A. W. Robertson, C. S. Allen, Y. A. Wu, K. He, J. Olivier, J. Neethling, A. I. Kirkland, and J. H. Warner, Nature Communications 3, 1144 (2012).

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References

[15] J. Kotakoski, A. Krasheninnikov, U. Kaiser, and J. Meyer, Physical Review Letters 106, 105505 (2011).

[16] J. Kotakoski, J. Meyer, S. Kurasch, D. SantosCottin, U. Kaiser, and A. Krasheninnikov, Physical Review B 83, 245420 (2011).

[17] J. C. Meyer, S. Kurasch, H. J. Park, V. Skakalova, D. Künzel, A. Gross, A. Chuvilin, G. AlgaraSiller, S. Roth, T. Iwasaki, U. Starke, J. H. Smet, and U. Kaiser, Nature Materials 10, 209 (2011).

[18] B. Westenfelder, J. C. Meyer, J. Biskupek, S. Kurasch, F. Scholz, C. E. Krill, and U. Kaiser, Nano Letters 11, 5123 (2011).

[19] R. F. Egerton, Microscopy Research and Technique 75, 1550 (2012).

[20] R. Zan, C. Muryn, U. Bangert, P. Mattocks, P. Wincott, D. Vaughan, X. Li, L. Colombo, R. S. Ruoff, B. Hamilton, and K. S. Novoselov, Nanoscale 4, 3065 (2012).

[21] N. N. Klimov, S. Jung, S. Zhu, T. Li, C. A. Wright, S. D. Solares, D. B. Newell, N. B. Zhitenev, and J. A. Stroscio, Science 336, 1557 (2012).

[22] P. Xu, Y. Yang, S. Barber, M. Ackerman, J. Schoelz, D. Qi, I. Kornev, L. Dong, L. Bellaiche, S. Barraza-Lopez, and P. Thibado, Physical Review B 85, 121406R (2012).

[23] F. Eder, J. Kotakoski, K. Holzweber, C. Mangler, V. Skakalova, and J. C. Meyer, Submitted (2012).

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probes are separated only by the thickness of the graphene membrane. This allows us for the first time to directly measure the deformations induced by one STM probe on a free-standing membrane with an independent second probe [23].

0ral Organic light emitting diodes using graphene electrodes 1

Philips Research, Weisshausstrasse 2, 52066 Aachen, Germany Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK 3 Graphenea S.A., Tolosa Hiribidea 76, E-20018 Donostia, San Sebastian, Spain

1

Jens Meyer 2 P. R. Kidambi 1 C. Weijtens A. Centeno3 3 A. Zurutuza 2 J. Robertson and 2 S. Hofmann

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Electrode materials combining high electrical conductivity and optical transparency are crucial components for organic light emitting diodes (OLED). Graphene is thereby a highly promising alternative to commonly used Indium tin oxide (ITO), in particular considering that unlike ITO graphene is flexible and, when grown via Chemical Vapor Deposition (CVD), not constraint by limited natural resources. Critical challenges for graphene based OLEDs not only relate to the further improvement of large-area, controlled graphene CVD [1,2], but also to its integration, in particular to achieve efficient charge injection and graphene doping. Several dopants have recently been introduced, but most are chemically not stable or not applicable for organic electronic devices.

In the Figure 1 we show that transition metal oxides, such as MoO3, are very efficient and stable p-type dopants for graphene which can be easily integrated in the OLED fabrication process. Our process is based on scalable graphene CVD [1,2] and the doping is carried out via thermal evaporation analogous to all following OLED layers.

With in-situ 4-point probe measurements we find that only a few nanometers of MoO3 are sufficient for efficient doping leading to a more than threefold improved sheet resistance.

In addition, ultra-violet and x-ray photoemission spectroscopy (UPS, XPS) studies of the doping process reveal a large interface dipole of 2.2 eV and band bending caused by an electron transfer from graphene to MoO3. The strong p-doping of graphene is enforced by the deep lying electronic states of MoO3 which exhibits a work function of >6.5 eV.[3] The energy level alignment at the graphene/MoO3/organic interfaces as measured

jens.meyer@philips.com

with UPS shows only very small energy barriers for hole-injection.

Thus, MoO3 allows not only an efficient p-doping of graphene, but also provides a suitable matching for efficient hole-injection from graphene into the OLED layers. Based on this process, we demonstrate CVD graphene based OLEDs that show electro-optical performances similar to conventional ITO based devices, as shown in Figure 2.

Acknowledgements: The authors acknowledge funding from the EC project Grafol.

References [1] Kidambi et al., J. Phys. Chem. C (2012) DOI 10.1021/jp303597m.

[2] Weatherup et al., ACS Nano (2012) DOI 10.1021/nn303674g.

[3] Meyer et al., Adv. Mater. (2012), 24, 5408.

Figures

Figure 1: Scheme of OLEDs with ITO electrode and graphene electrode s.

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Figure 2: Current efficiency vs. voltage characteristics of OLEDs with ITO and graphene electrode, respectively.

0ral Ultra-wideband graphene photodetectors for photonic integrated circuits

1

Thomas Mueller 1 A. Pospischil 2 M. Humer M. M. Furchi1 2 R. Guider and 2 T. Fromherz

Vienna University of Technology, Institute of Photonics, Gußhausstraße 27-29, 1040 Vienna, Austria 2 Johannes Kepler University Linz, Institut für Halbleiter und Festkörperphysik, Altenbergerstraße 69, 4040 Linz, Austria

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Graphene is a two-dimensional electron system comprised of a single atomic layer of carbon. It has unique physical properties, such as linear electronic dispersion, zero effective mass, and extraordinary high carrier mobility. Despite the absence of an electronic band gap, graphene also holds great promise for applications in photonics and optoelectronics. Photocurrent experiments have demonstrated a strong response near metal/graphene interfaces with an internal quantum efficiency of up to 30 %. The high photocurrent generation efficiency is related to the high carrier velocity, which leads to an ultrafast separation of the photo-generated carriers near local potential variations, such as they exist near metal/graphene interfaces.

In ultrafast photocurrent measurements [1, 2], no photoresponse degradation was observed up to 40 GHz, demonstrating the feasibility and unique benefits of using graphene in high-bandwidth optical communication systems. A metal-graphene-metal photodetector [3], consisting of a large number of inter-digitated finger electrodes, was used for the faithful detection of an optical bit stream at a data rate of 10 Gb/s. Integration of a metal-graphenemetal photodetector into an optical microcavity [4] allowed to increase the inherently low (2.3 %) optical absorption in single-layer graphene to >60%.

Here, we demonstrate the first monolithic integration of a graphene-based photodetector with a silicon-on-insulator waveguide [5]. Ultrawideband operation across all optical telecommunication windows, from O- to U-band, is achieved. Such a broad operation range cannot be achieved with materials that are traditionally used in silicon photonics, such as strained germanium, whose responsivity range is limited by its band gap. Our work complements the recent

1

thomas.mueller@tuwien.ac.at

demonstration of a CMOS-integrated graphene electro-optical modulator [6], paving the way for carbon-based optical interconnects.

A schematic illustration of the device structure is shown in Figure 1 (a). The devices were fabricated on a silicon-on-insulator (SOI) wafer with 270 nm thick Si device layer and 3 μm buried oxide. A 600 nm wide waveguide was defined using lithography and etched by reactive-ion etching. The wafer was then covered with a 7 nm thick layer of SiO2 and a sheet of graphene (≈25×25 μm2 in size) was transferred to the desired location on the waveguide. Contact electrodes were fabricated by electron-beam lithography and Ti/Au sputtering.

Finally, the sample was cleaved in order to obtain a clean facet for the in-coupling of light. The optical mode in the waveguide is absorbed as the light propagates along the graphene sheet. The potential gradient, originating from different dopings in the metal-covered and uncovered parts of graphene [1,3], drives a photocurrent (PC) towards the ground leads, as illustrated in Figure 1 (b). Due to the lack of an electronic band gap in graphene, the photo-generated carriers pass through the potential barriers at the GNDelectrodes almost unimpeded, leading to highbandwidth photodetection even without S-GND bias, and hence without dark-current. A careful design of the device geometry was performed in order to evaluate the tradeoff in photoresponsivity due to the optical absorption in the signal electrode. For achieving optimum performance, it is necessary to keep the signal electrode width as small as possible. On the other hand, the contact resistance increases with decreasing electrode width, giving rise to reduced photocurrent and reduced RC-bandwidth.

The performance characteristics of a 24 μm long bilayer graphene device with 180 nm wide signal

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electrode was determined by coupling laser light (1.55 μm wavelength) into the silicon waveguide using a lensed single-mode fiber (2.5 μm spot diameter). The optical power at the input port of the waveguideintegrated photodetector was estimated from transmission measurements of reference waveguides without photodetector. The photo-responsivity, defined as the ratio of the measured photocurrent to the input optical power, was determined to be 0.05 A/W – an order of magnitude higher than that achieved with normal-incidence photodetectors [3].

The wavelength-dependence of the photo-response was measured using two separate light sources: a laser operating at a fixed wavelength of 1310 nm (Oband), and a second laser, tunable in the range 1550–1630 nm (from the C-band, across all over the Lband, into the U-band). It was found that the responsivity is entirely flat across all telecommunication bands, unlike the drastic decrease of the response of Ge photodetectors beyond 1550 nm, or strained Ge detectors beyond 1605 nm. We expect the device to work at even longer wavelengths; limited only by the cut-off properties of the silicon waveguide.

Because InGaAs cannot be monolithically integrated with silicon CMOS, other materials are currently being investigated for photodetection in the L- and U-bands. Among them, ion-implanted Si and GeSn are considered the most promising ones.

Our graphene photodetectors outperform devices based on these materials in several respects.

Implanted Si detectors suffer from low optical absorption, resulting in device footprints that are 10–100 times larger than what we achieve with graphene. GeSn photodetectors, on the other hand, exhibit high dark currents, whereas our devices can be operated without bias (and hence without dark current).

[5] A. Pospischil, M. Humer, R. Guider, T. Fromherz, and T. Mueller, to be published.

[6] M. Liu, X. Yin, E. Ulin-Avila, B. Geng, T. Zentgraf, L. Ju, F. Wang, and X. Zhang, Nature 474 (2011) 64.

Figures

Figure 1: (a) Schematic drawing of a silicon waveguide integrated graphene photodetector. (b) Potential profile in the graphene sheet. The GND-S-GND configuration allows doubling of the photocurrent.

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[1] F. Xia, T. Mueller, Y. Lin, A. Valdes-Garcia, and Ph. Avouris, Nature Nanotechnol. 4 (2009) 839.

[2] A. Urich, K. Unterrainer, and T. Mueller, Nano Lett. 11 (2011) 2804.

[3] T. Mueller, F. Xia, and Ph. Avouris, Nature Photon. 4 (2010) 297.

[4] M. Furchi, Nano Lett. 12 (2012) 2773.

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References

0ral Spin-Relaxation Phenomena in Graphene: Proximity-Induced SpinOrbit Coupling Yields Novel Type of Ultrafast Spin Relaxation

Frank Ortmann D. Van Tuan D. Soriano and S. Roche

Frank.Ortmann@icn.cat

CIN2 (ICN-CSIC) and Universitat Autonoma de Barcelona, Catalan Institute of Nanotechnology, Campus UAB, Bellaterra, Spain

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Spin transport and spin relaxation are intriguing and strongly debated phenomena in graphene, first, because of unexpectedly short spin diffusion times despite vanishingly small intrinsic spin-orbit interaction and hyperfine coupling, but also because of controversially debated spin relaxation mechanisms.

On the other hand, proximity induced spin-orbit coupling can trigger interesting phenomena in graphene such as the quantum spin Hall effect [1], which can be realized by single ad-atom deposition [2]. Similarly, the intercalation of Au atoms between graphene and a Ni(111) surface has been shown to create giant spin-orbit splitting at the Dirac point reaching 100 meV [3] even for dilute cases, thus demonstrating the efficiency of such proximity effects.

We explore the effect of spin-orbit interaction induced by dilute ad-atom deposition on graphene by means of an efficient time-propagation approach. We monitor the spin-dynamics of initially polarized states that propagate in graphene under presence of such impurities and extract spin precession times and spin-relaxation times. From a comparison to the momentum scattering time we infer different relaxation mechanisms which can only partially be described with established Dyakonov-Perel and Elliot-Yafet mechanisms. We analyze various crossovers as a function of Fermi-level position and momentum scattering time which can be tuned by the disorder potential.

We will also comment on the influence of the direction of the initial spin polarization.

References [1] C. L. Kane and E. J. Mele, Phys. Rev. Lett. 95, 226801 (2005).

[2] C. Weeks, J. Hu, J. Alicea, M. Franz, and R. Wu, Phys. Rev. X 1, 021001 (2011).

[3] D. Marchenko, A. Varykhalov, M. R. Scholz, G. Bihlmayer, E. I. Rashba, A. Rybkin, A. M. Shikin, and O. Rader, Nature Comm. 3, 1232 (2012).

[4] D. V. Tuan, F. Ortmann, D. Soriano, and S. Roche (submitted).

Figures

Figure 1: (a) Graphene with ad-atom impurities adsorbed on hollow sides that induce an effective spin-orbit interaction. (b) Spinpolarization dynamics over time for out-of-plane spin injection. Spin decay depends on the Fermi energy.

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0ral Growth and Characterization of Graphene / Hexagonal Boron Nitride Heterostack on Cu(111)

Jürg Osterwalder 1 S. Roth 2 F. Matsui T. Greber1

1

osterwal@physik.uzh.ch 1

Physik-Institut, Universität Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland Permanent address: Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192, Japan 2

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References [1] A. Geim, K. Novoselov, Nature Materials, 6 (2007) 183.

[2] C. R. Dean et al., Nature Nanotechnol., 5 (2010) 722.

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small spread in crystal orientations of not more than 3°, which is consistent with the observation of moiré patterns observed for this system in a recent low-temperature scanning tunneling microscopy (STM) study [14].

The growth of graphene on top of the h-BN layer required much higher precursor pressures and exposure times. X-ray photoelectron spectroscopy (XPS) data confirm the presence of a single graphene layer with the desired stacking sequence of graphene/h-BN/Cu(111). In the ARPES data the graphene π band is observed with the characteristic linear dispersion up to the Fermi energy (Fig. 1b), leading to a six-fold arrangement of maxima in the Fermi surface map displayed in Fig. 1c. No indication of a band gap is observed in these data.

In this talk, a detailed structural characterisation of this graphene/boron nitride heterostack will be presented, showing that the largely predominant phase on the surface features a graphene layer that matches the orientation of the h-BN lattice but exhibits a lattice mismatch of the order of 1.41.6%, similar to the mismatch between graphite and bulk h-BN. This presence of this phase is confirmed by the observation of the characteristic moiré pattern in STM images. A weak electronic coupling between the two layers arises due to this incommensurate growth, which can rationalize the absence of a band gap in the graphene layer.

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Graphene offers great potential for applications in electronic devices [1], but in order to transfer this potential to the industrial scale, production methods for high quality material are vigorously investigated, as well as suitable substrate materials. Hexagonal boron nitride (h-BN) has appeared as a natural candidate substrate due to its closely related structure, its flatness and its wide band gap. It could be shown, by building devices using standard exfoliation techniques, that h-BN supported graphene exhibits superior electronic properties [2], and that few layers of hBN can be used as a barrier in a fieldeffect tunneling transistor [3]. Several groups have reported direct growth of graphene on h-BN on metal surfaces in a two-step chemical vapor deposition (CVD) process: on Ni(111) [4,5], Ru(0001) [6], polycrystallinge Cu foils [7], as well as on Ni(111) films on W(110), and with Au intercalated between the h-BN and the Ni(111) [8].

Building on our long-term experience in the growth of epitaxial single-layer h-BN [9,10] and graphene [11-13] films on metal surfaces, we have investigated the sequential CVD growth of a single graphene layer on a predeposited single h-BN layer on Cu(111). Borazine (HBNH)3 [4] and 3pentanone (C2H5COC2H5) [13] were used as precursors for h-BN and graphene growth, respectively. Substrate temperatures were of the order of 1000 K, and borazine dosing was done at a pressure in the 10-6 mbar range, leading to the self-saturating growth of a single h-BN layer on the Cu(111) surface. Low-energy electron diffraction (LEED), x-ray photoelectron diffraction (XPD) and angle-resolved photoemission (ARPES) data (Fig. 1a) testify for the presence of a well ordered boron nitride single layer. The LEED data show the h-BN lattice with a slightly smaller lattice constant and a

[3] L. Britnell et al., Science, 335 (2012) 947.

[4] A. Nagashima et al., Phys. Rev. B, 54 (1996) 13491.

[5] C. Oshima et al., Solid State Commun., 116 (2000) 37.

[6] C. Bjelkevig et al., J. Phys.: Condens. Matter, 22 (2010) 302002.

[7] Z. Liu et al., Nano Letters, 11 (2011) 2032.

[8] D. Usachov et al., Phys. Rev. B, 82 (2010) 075415.

[9] W. Auwärter et al., Surf. Sci., 429 (1999) 229.

[10] M. Corso et al., Science, 303 (2004) 217.

[11] D. Martoccia et al., Phys. Rev. Lett., 101 (2008) 126102.

[12] T. Brugger et al., Phys. Rev. B 79 (2009) 045407.

[13] S. Roth et al., Surf. Sci., 60 (2011) L17.

[14] S. Joshi et al., Nano Letters 12 (2012) 5821.

Figures

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Figure 1: He IIÎą (40.8 eV) excited ARPES data from (a) a single layer h-BN on Cu(111) and from (b) a graphene/h-BN/Cu(111) stack, both measured along the direction of the two-dimensional Brillouin zone. In (c), a Fermi surface map of the graphene/h-BN/Cu (111) stack is displayed, showing six dominant spots associated with Dirac cones. (d) Intensity distributions along a circular path in (c), crossing all six Dirac points. In (a), the sharp feature appearing between 2 eV binding energy and the Fermi energy is from the fast dispersing sp band of the Cu(111) substrate.

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Invited Colossal Enhancement of Spin-Orbit Coupling in Weakly Hydrogenated Graphene

Barbaros Özyilmaz

Department of Physics, 2 Science Drive 3, National University of Singapore, Singapore Graphene Research Centre, 6 Science Drive 2, National University of Singapore, Singapore 117546

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Graphene’s extremely small intrinsic spin-orbit (SO) interaction1 makes the realization of many interesting phenomena such as topological/quantum spin Hall states and the spin Hall Effect (SHE) practically impossible. Recently, it was predicted that the introduction of adatoms in graphene would enhance the SO interaction by the conversion of sp2 to sp3 bonds. However, introducing adatoms and yet keeping graphene metallic, i.e., without creating electronic (Anderson) localization8, is experimentally challenging. Here, we show that the controlled addition of small amounts of covalently bonded hydrogen atoms is sufficient to induce a colossal enhancement of the SO interaction by three orders of magnitude. This results in a SHE at zero external magnetic fields at room temperature, with nonlocal spin signals up to 100 Ω; orders of magnitude larger than in metals. The non-local SHE is, further, directly confirmed by the Larmor spin-precession measurements. From this and the length dependence of the non-local signal we extract a spin relaxation length ~ 1 μm, a spin relaxation time ~ 90 ps and a SO strength of 2.5 meV

Invited Atom-Thick Materials for the Next Revolution in Electronics

Massachusetts Institute of Technology 77 Massachusetts Ave., Bldg. 39-567B, Cambridge, MA-02139, USA

Tomás Palacios H. Wang, L. Yu A. Hsu, X. Zhao B. Mailly, C. Mackin Y.-Hsien, Y. Shi M. Dresselhaus and J. Kong tpalacios@mit.edu

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Electronics is at a crossroads. The materials and technologies that have enabled the information revolution of the last 60 years are quickly reaching their ultimate physical limit. Fortunately, a new generation of atom-thick materials has recently been discovered. This talk will review these new materials, all of them less than one nanometer thick, and the novel devices and applications enabled by their amazing properties.

Graphene was the first one of these materials to be discovered. A two-dimensional structure of carbon atoms with sp2 bonding, graphene has demonstrated the highest electron and hole mobility at room temperature in any semiconductor material. Its transport properties make it ideal for all kind of non-linear analog electronics, it shows extremely high frequency performance, and its one-atom-thickness enables transparent and highly flexible electronics.

MoS2 and other transition metal dichalcogenides (TMD) materials are another example of twodimensional materials with unique properties.

Made of only three-atoms thick, they can complement graphene to build flexible digital and mixed-signal circuits, overcoming its lack of bandgap while still sharing many of graphene’s excellent mechanical and thermal properties. We will describe some of our recent results on the development of 2D nanoelectronics on MoS2 and TMD materials. First, large-area single-layer MoS2 material is grown by chemical vapor deposition (CVD) that makes the wafer-scale fabrication of MoS2 devices and circuits possible for the first time. Second, the top-gated transistors, fabricated for the first time on single-layer MoS2 grown by CVD, show multiple state-of-the-art characteristics, such as high mobility, ultra-high on/off current ratio, record current density and current

saturation. Finally, the first fully integrated digital and analog circuits based on MoS2 are constructed to demonstrate its capability for both logic and mixed-signal applications. Key circuit building blocks for digital and analog electronics such as inverter, NAND gate, memory and ring oscillator circuits are demonstrated.

References [1] H. Wang, A. . Hsu, and T. Palacios, “Graphene electronics for RF applications,” Microwave Magazine, IEEE, vol. 13, no. 4, pp. 114–125, 2012.

[2] H. Wang, L. Yu, Y.-H. Lee, Y. Shi, A. Hsu, M. L. Chin, L.-J. Li, M. Dubey, J. Kong, and T. Palacios, “Integrated Circuits Based on Bilayer MoS2 Transistors,” Nano Lett., vol. 12, no. 9, pp. 4674–4680, Sep. 2012.

Figures

Figure 1: a) Graphene transistors and chemical sensors transferered to a transparent, flexible substrate. b) Optical micrograph of a MoS2 integrated circuit, a 5-stage ring oscillator.

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Invited Graphene for Electronic Devices

Seongjun Park

s3.park@samsung.com

References [1] H. Yang, J. Heo, S. Park, H. J. Song, D. H. Seo, K.-E. Byun, P. Kim, I. Yoo, H.-J. Chung, and K. Kim, 336 (6085), pp 1140-3 (2012).

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Graphene has been considered as one of the candidate materials to extend Si-technology due to its unique electronic properties including high carrier mobilities. However, graphene has no bandgap and it is difficult to achieve high IOn/IOff ratio, one of the most important requirements for electronic devices. Recently, we proposed and demonstrated a new device structure, Barristor, based on one of the unique properties of graphene, work function tunability. [1] The key feature of the device is the modulation of Schottky barrier height between Graphene-Si through the gate voltage modulation. Our device has major advantages over previously investigated graphene field effect transistors (FET). Large IOn/IOff ratio of 105 can be achieved. It has no fundamental issues on mobility degradations, since our device does not alter the given properties of graphene. In addition, our device is fully compatible with current Si technology and we were able to fabricate the devices with 6 inch wafer scale with CVD (Chemical Vapor Deposition) grown graphene.

In this presentation, we will discuss about the details of Barristor including the device characteristics. We will also present recently developed vertical transistor based on asymmetric junctions. In addition, we will discuss the current issues on wafer scale developments and their potential solutions. Finally, we will cover the potential applications of graphene within semiconductor industry.

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Samsung Advanced Institute of Technology (SAIT), 97 Samsung2-ro, Giheung-gu, Gyeonggi-do, Korea 446-712

Invited Supercollision cooling in undoped graphene

bernard.placais@lpa.ens.fr

Laboratoire Pierre Aigrain, ENS-CNRS UMR 8551, 24 rue Lhomond, 75231 Paris Cedex 05, France

Carrier mobility in solids is generally limited by electron-impurity or electron–phonon scattering, depending on the most frequently occurring event. Three-body collisions between carriers and both phonons and impurities are rare; they are denoted supercollisions (figure).

Elusive in electronic transport they should emerge in relaxation processes as they allow for larger energy transfers [1]. This is the case in undoped graphene, where the small Fermi surface drastically restricts the allowed phonon energy in ordinary collisions. Using electrical heating and sensitive noise thermometry we report on supercollision cooling in diffusive monolayer graphene [1]. At low carrier density and high phonon temperature the Joule power P obeys a PαTe3 law as a function of electronic temperature Te. It overrules the linear law expected for ordinary collisions which has recently been observed in resistivity measurements. The cubic law is characteristic of supercollisions and departs from the Te4 dependence recently reported for doped graphene below the Bloch–Grüneisen temperature [2]. These supercollisions are also observed in photocurrent relaxation [4] important for applications of graphene in bolometry [5] and THz photo-detection [6].

References

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[1] J. C. W. Song, M. Y. Reizer, L.S. Levitov, Phys. Rev. Lett. 109 (2012) 106602.

[2] A.Betz, SH.Jhang, E.Pallecchi, R.Ferreira, G. Fève, J.M. Berroir, B. Plaçais, Nat. Phys. 9 (2013) 109.

Bernard Plaçais A. C. Betz, S. H. Jhang E. Pallecchi, R. Ferreira G. Fève and J-M. Berroir

[3] A.C. Betz, F. Vialla, D. Brunel, C. Voisin, M. Picher, A. Cavanna, A. Madouri, G. Fève, J.M. Berroir, B. Plaçais, E. Pallecchi, Phys.

Rev. Lett. 109 (2012) 056805.

[4] M.W. Graham, S-F. Shi, D.C. Ralph, J. Park, P.L. McEuen, Nature Phys. 9 (2013) 103.

[5] K.C. Fong, K.C., Schwab, Phys. Rev. X 2 (2012) 031006.

[6] C. B. McKitterick, D. E. Prober, B.S. Karasik, J. Appl. Phys. 113 (2013) 044512.

Figures

Figure 1: Tunability of the Bloch–Grüneisen temperature and noise thermometry set-up. a, Electron–phonon interactions scatter carriers from one point on the Fermi surface (red circle) to another, within the boundary of the available phonon space (blue circle). In low-temperature regime (Tph <TBG), qmax is smaller than 2kF, which represents a full backscattering of electrons. b, The Fermi surface shrinks as the carrier density decreases, resulting in a smaller value of TBG. Here, when Tph=TBG, qmax just equals 2kF. c, In the vicinity of the charge neutrality point, one enters the high-temperature regime, where Tph >TBG. Here, only phonons with q≤2kF can scatter off the electrons in the ordinary collisions (green arrows), whereas the entire thermal distribution of phonons is allowed for disorder-assisted supercollisions (purple arrow).

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Oral Electron and Optical Spectroscopies of Graphene Nanoribbons: Insights from Ab-Initio Calculations 1

Istituto Nanoscienze, Consiglio Nazionale delle Ricerche, 41125 Modena, Italy Dept of Physics, Informatics and Mathematics, University of Modena & Reggio, 41125 Modena, Italy 3 Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, CH 4 Swiss Light Source, Paul Scherrer Institut, 5232 Villigen, CH 5 Max Planck Institut for Polymer Research, 55128 Mainz, Germany 6 Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, CH

1

Deborah Prezzi

A. Ferretti1, S. Wang1 A. Ruini1,2, E. Molinari1,2 P. Ruffieux3, J. Cai3 N. C. Plumb4, L. Patthey4 X. Feng5, K. Müllen5 C. A. Pignedoli3 and R. Fasel3,6

2

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[1] D. Prezzi, D. Varsano, A. Ruini, A. Marini, and E. Molinari, Phys. Rev. B, 77 (2008) 041404;

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the exchange-correlation potential, using a planewave basis set and pseudopotentials. We carefully checked the effect of van der Waals corrections. We find a graphene/Au distance of 3.31 Å and a negligible electronic interaction (i.e. band hybridization), in excellent agreement with existing literature. For the H-passivated 7-AGNR we determine an average C-Au distance of 3.15 Å, and little to negligible band hybridization of the electronic bands of GNRs and Au(111). Our findings clearly show a weak interaction between 7-AGNR and the Au(111) metal substrate. In order to compare ARPES and STS experiments, we have computed the self-energy corrections to the electronic structure by means of many-body perturbation theory, within the so-called GW approximation at the G0W0 level. As depicted in Fig. 2 (left-hand side), the GW correction brings the LDA gap from 1.6 to 3.7 ± 0.1 eV [2]. We then estimated the gap reduction due to the presence of the metallic substrate by adding the image charge (IC) correction to the GW energy gap of the isolated GNR (Fig. 2, right-hand side). Overall, this results in a theoretical estimate of the energy band gap of 2.3 to 2.7 eV for the 7-AGNR on Au(111), which is in very good agreement with the experimental value of 2.3 ± 0.1 eV. The above results show that our ab-initio theoretical scheme can provide quantitative predictions for electron spectroscopies of nanoribbons on weakly coupled substrates such as Au. Recent results for optical excitations and excitonic effects will also be discussed, including the spectral evolution from molecular and polymer precursors to nanoribbons.

References

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Graphene nanostructures have striking properties related to the lateral confinement that can open a band gap and induce semiconducting behavior with controlled quantum states and a variety of peculiar width- and edge-related phenomena depending on the details of the atomic structure.

Radically new functionalities can thus be designed, far beyond those expected from extended graphene systems or conventional semiconductors.

Key features connected to the tunability of electronic and optical properties as a function of structural parameters, e.g. width and edge structure of graphene nanoribbons (GNR), have been predicted theoretically (see e.g. [1-2]); however, only recently atomic control of GNR geometry (orientation, width and edge termination) was demonstrated by a novel approach based on depositing molecular precursors on appropriate substrates, which catalyze polymerization and ribbon formation [3].

These advancements in the fabrication procedure have thus allowed the first measurements (Fig. 1) of the band gap and the topology of the occupied bands of atomically precise armchair GNRs (AGNR’s) by scanning tunneling spectroscopy (STS) and angle-resolved photoelectron spectroscopy (ARPES) techniques [4,5].

In this work we combine cutting edge theoretical and experimental techniques to study the electronic structure of a specific armchair nanoribbon (N=7, 7-AGNR). In particular we compare many-body perturbation theory calculations (performed at the GW level) with ARPES and STS data. First principles calculations based on Density Functional Theory (DFT) were carried out for 7-AGNR, both isolated and on Au(111) substrate. Calculations were performed within the local-density approximation (LDA) for

deborah.prezzi@nano.cnr.it

[2]

[3]

[4]

[5]

D. Prezzi, D. Varsano, A. Ruini, and E. Molinari, Phys. Rev. B, 84 (2011) 041401, and refs therein.

C. Cocchi, A. Ruini, D. Prezzi, M. J. Caldas, and E. Molinari, J. Phys. Chem. C, 115 (2011) 2969; C. Cocchi, D. Prezzi, A. Ruini, M. J. Caldas, and E. Molinari, J. Phys. Chem. Lett., 2 (2011) 1315.

J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, M. Muoth, A. P. Seitsonen, M. Saleh, X. Feng, K. Mullen, and R. Fasel, Nature, 466 (2010), 470.

P. Ruffieux, J. Cai, N. C. Plumb, L. Patthey, D. Prezzi, A. Ferretti, E. Molinari, X. Feng, K. Mullen, C. A. Pignedoli, and R. Fasel, ACS Nano, 6 (2012) 6930.

S. Linden et al., Phys. Rev. Lett., 108 (2012) 216801.

Figure 2: LDA and GW-corrected DOS (energy gap highlighted) for the gas phase 7-AGNR are shown on the left side. By taking into account the surface screening, the gap is reduced to 2.3 - 2.7 eV, as shown on the right side. The molecule-Au(111) distance has been estimated to be 3.15 Ă&#x2026;.

Figures

140

Figure 1: (a) Scanning tunneling microscopy (STM) image (U = 2.2 V, I = 0.15 nA, 5 K) and chemical structure of an armchair graphene nanoribbon of width N= 7 (7-AGNR) on Au(111) (b) ARPES intensity plot I(E EF,k||) recorded along the ribbon axis revealing the two occupied frontier bands (raw data, hν = 37 eV, T = 300 K). The atomic structure of the H-terminated 7-AGNR is reported for clarity.

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Oral 1

Fabrication of Graphene on Copper Using Photo-Thermal Chemical Vapour Deposition

Juha Riikonen 1 1 W. Kim , C. Li 1 O. Svensk S. Arpiainen2and 1 H. Lipsanen

1

juha.riikonen@aalto.fi

Aalto University, Department of Micro- and Nanosciences, Micronova, P.O. Box 13500, FI-00076 Espoo, Finland 2 VTT Technical Research Centre of Finland, Microsystems and Nanoelectronics, P.O. Box 1000, FI 02044 VTT, Espoo, Finland

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Raman mapping reveals high intensity ratio for 2D to G bands (mode I2D/IG ~ 3.4 for scanned area of 25 µm × 25 µm). All in all, our study shows that PTCVD can be used for the fabrication of highquality single-layer graphene on copper with high throughput and is therefore a promising method for cost-effective graphene fabrication.

Figures

GRAPHENE 2013

Figure 1: Raman spectrum of a graphene film fabricated at 950 °C (transferred onto a 300 nm SiO2/Si). Inset shows histogram distribution of 2D to G band ratio determined from an area of 25 × 25 µm2.

141

Fabrication of single-layer graphene films on copper foils by photo-thermal chemical vapor deposition (PTCVD) is demonstrated. The PTCVD furnace was realized installing additional gas controls in a rapid thermal processing (RTP) system typically used in wafer scale CMOS processing. The cold-wall RTP utilizes halogen lamps as a heat source. One significant benefit of using cold-wall RTP chamber compared to conventional hot-wall tube furnaces is the minimization of contaminating particles originating from the side walls. Photothermal heat source enables also faster heating and cooling rates compared to resistive heating due to minimized thermal mass. In industrial point of view, PTCVD can provide cost-efficiency due to batching capability and minimized process cycle times. Additionally, the process is straightforward to upscale as the temperature can be controlled over large areas in real-time. The PTCVD process using methane precursor in low pressure (10 mbar) shows very high growth rate as depending on the synthesis parameters uniform single-layer graphene films can be grown on copper only in 15 to 60 s. The pre-annealing step of copper foil carrier out in the PTCVD chamber at the growth temperature was 5 min. In addition to the obvious advantage of increased throughput, the capability of performing rapid process at high temperatures is also an effective way to reduce the deleterious copper evaporation. The effect of various synthesis parameters was studied by characterizing the crystalline quality, thickness and electronic properties of the films. The quality of the graphene films is equivalent to a typical CVD graphene. For example, as pointed out in Figure 1 the disorder induced D peak is not visible in the Raman spectra (Elaser = 2.33 eV) in graphene films fabricated at 950 °C (and transferred to a 300-nmthick SiO2/Si substrate). Moreover, the confocal µ-

Invited Graphene for Flexible Electronics

Tapani Ryh채nen

Head of Sensor and Material Technologies Laboratory Nokia Research Center, Finland

tapani.ryhanen@nokia.com

142

The chemical, electrical, optical, mechanical and thermal properties of grapheme make it an interesting new material for a multitude of applications. In the electronics industry graphene is expected to become a signicant new technology platform that creates applications ranging from functional composite materials to integrated circuits and printed electronics. This paper will discuss the use of graphene in manufacturing novel electronic devices based on flexible and stretchable electronics. Opportunities to improve the properties of the key components of flexible electronics, such as, batteries, supercapacitors, sensors, transmission lines, touch screen, transistors, are discussed. Examples of Nokia's results related to electronics, optoelectronics and electrochemistry will be shown, with a vision of their impact in radio, sensor, battery and computing technologies. Applications of graphene in solar cells, batteries, supercapacitors and fuel cells are summarised, and graphene as a conductive ink for printed electronics is also discussed. Finally, the presentation discusses an industrial vision of graphene as a new technology platform, the challenges in creating new value networks and chains, the European position in graphene industrialisation, and opportunities for new manufacturing based on graphene. The flexible electronics work in the EU FET Graphene Flagship project will be shortly introduced.

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Oral Atomically precise graphene nanoribbons: Electronic structure, optical properties and vibrational characteristics

1

Juan R. Sanchez-Valencia 1 1 J. Cai , H. Söde 1 2 P. Ruffieux , R. Denk M. Hohage2, P. Zeppenfeld2 3 3 X. Feng , K. Müllen 1 and R. Fasel

1

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trivial task. Transmittance measurements would obviously require the use of optically transparent substrates and thus suitable transfer methods away from metallic substrates. Therefore, reflectance measurements appear more suitable for investigating the optical properties of GNRs supported on metallic substrates. We have applied Reflectance Difference Spectroscopy (RDS) [11] a spectroscopic technique that determines the difference in normal reflectivity of two orthogonal linearly polarized beams. This technique relies on the use of anisotropic materials, i.e. materials that present different optical properties in two orthogonal directions. To allow for RDS measurements of GNRs, we have aligned the nanoribbons along a single preferential direction.

This has been achieved by using vicinal metallic surfaces such as Au(788). We present in situ RDS data acquired in UHV at different stages of the GNR fabrication process. RDS data were taken after annealing the samples at different temperatures allowing to monitor the different stages of growth: monomer deposition, monomer coupling and polymer dehydrogenation. After each annealing step, the same samples were imaged with Scanning Tunneling Microscopy (STM) to characterize the GNR structures. In addition, we have characterized the vibrational properties of the GNRs by ex situ Raman spectroscopy that contains valuable information about the ribbon nanostructure. All of these results will be discussed in relation to the electronic properties of the GNRs as determined from photoemission and scanning tunneling spectroscopy data.

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Graphene nanoribbons (GNRs) – narrow stripes of graphene [1] – are predicted to be semiconductors with an electronic band gap that sensitively depends on the ribbon width [2]. The electronic properties of GNRs also strongly depend on the arrangement of the carbon atoms in the ribbon structure. For armchair GNRs (AGNRs) the band gap is inversely proportional to the ribbon width.

Zigzag GNRs (ZGNRs), on the other hand, are predicted to present spin polarized edges. Their gap opens thanks to an unusual antiferromagnetic coupling between the magnetic moments at opposite edge carbon atoms. These versatile characteristics allow the design of GNR-based structures with widely tunable electronic properties, but require highest (i.e. atomic) structural precision. With our recently developed bottom-up approach the fabrication of atomically precise AGNRs [3] can be achieved using specifically designed precursor monomers. The monomers are sublimed in ultrahigh vacuum (UHV) and deposited onto metallic substrates such as Au or Ag. Substrate catalyzed dehalogenation of the monomers induces the formation of linear polymers that are subsequently cyclodehydrogenated to form the desired GNRs. With this approach, we have fabricated ultranarrow GNRs and related graphene nanostructures for experimental investigations of their structural and electronic properties [3-10]. For the case of N=7 AGNRs (7-AGNRs), the electronic band gap and dispersion of the occupied electronic bands have been determined with high precision [9].

The opening of a band gap for GNRs modifies the optical properties, showing specific absorption that contains information about electronic transitions. Optical characterization of GNRs supported on metal substrates, however, is a non-

juan-ramon.sanchez@empa.ch

143

Empa, Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Lab. Überlandstrasse 129, Dübendorf (Switzerland).

2 Institute of Experimental physics, Johannes Kepler University Linz, Altenbergerstr.

69, 4040 Linz, Austria 3 Max Planck Institute for Polymer Research, Ackermannweg 10, 55124 Mainz, Germany

References [1] [2] [3] [4] [5]

A. K. Geim, Science, 324 (2009) 1530.

V. Barone et al., Nano Lett., 6 (2006) 2748.

J. Cai et al., Nature, 466 (2010) 470.

M. Bieri et al., Chem. Commun., (2009) 6919.

M. Bieri et al., J. Am. Chem. Soc., 132 (2010) 16669.

[6] S. Blankenburg et al., Small, 6 (2010) 2266.

[7] M. Treier et al., Nature Chemistry, 3 (2011) 61.

[8] S. Blankenburg et al., ACS Nano, 6 (2012) 2020.

[9] P. Ruffieux et al., ACS Nano, 6 (2012) 6930.

[10] L. Talirz et al. JACS, 135 (2013) 2060.

[11] M. Hohage et al. Appl. Phys. A, 80 (2005) 1005.

Figures

Raman RDS 1.5

2.0

2.5

3.0

3.5

4.0

Photon energy (eV)

4.5

5.0

200

400

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800 1000 1200 1400 1600 1800 -1 Wavenumber (cm )

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Figure 1: STM pictures of a 7-AGNR with one visible terminus (top) and aligned ribbons on Au(788) surface (bottom). RDS (middle, left) reveals characteristic absorption features that can be directly linked to the electronic band structure of 7-AGNRs. Raman spectroscopy (middle, right) reveals the expected intensity distribution on G- and D-modes and the width-depending characteristic radial breathing like mode (RBLM) at ~400 cm-1.

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Oral SAM-like Arrangement of Thiolated Graphene Nanoribbons: Decoupling the Edge State from the Metal Substrate

1,3

Daniel Sánchez-Portal 1,2 P. Cabrera-Sanfelix and 1,3,4 A. Arnau

sqbsapod@ehu.es

1

Donostia Int. Physics Center (DIPC), Paseo Manuel de Lardizabal 4, San Sebastián 20018, Spain IKERBASQUE, Basque Foundation for Science, Bilbao48011, Spain Centro de Física de Materiales (CFM-MPC) CSIC-UPV/EHU, Paseo Manuel de Larizabal 5, San Sebastián 20018, Spain 4 Departamento de Física de Materiales UPV/EHU, Facultad de Química, Apdo. 1072, San Sebastián 20080, Spain 2 3

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References [1] Pepa Cabrera-Sanfelix, Andrés Arnau, Daniel Sánchez-Portal, Phys. Chem. Chem. Phys. 15 (2013) 3233-324.

Figures

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Figure 1: Magnetization density of a SAM-like arrangement of asymmetricallythiolated ultrathin ZGNRs on Au(111) and the corresponding band structure, where the polarized edge-state has been highlighted.

145

Density functional theory calculations have been used to analyze the electronic and magnetic properties of ultrathin zigzag graphene nanoribbons (ZGNR) with different edge saturations. We have compared a symmetric hydrogen saturation of both edges with an asymmetric saturation in which one of the edges is saturated with sulphur atoms or thiol groups, while the other one is kept hydrogen saturated.

The adsorption of such partially thiolated ZGNRs on Au(111) has also been explored. We have considered vertical and tilted adsorption configurations of the ribbons, reminiscent of those found for thiolated organic molecules in self-assembled monolayers (SAM) on gold substrates. We have found that saturation with sulphur atoms or thiol groups removes the corresponding edge state from the Fermi energy and kills the accompanying spin polarization.

However, this effect is so local that the electronic and magnetic properties of the monohydrogenated edge (H-edge) remain unaffected.

Thus, the system develops a spin moment mainly localized at the H-edge. This property is not modified when the partially thiolated ribbon is attached to the gold substrate, and is quite independent of the width of the ribbon.

Therefore, the upright adsorption of partially thiolated ZGNRs can be an effective way to decouple the spin-polarized channel provided by the H-edge from an underlying metal substrate [1]. These observations might open a novel route to build spin-filter devices using ZNGRs on gold substrates.

Oral Graphene-based Integrated Circuits: From an Inverter Towards a Ring Oscillator

Daniel Schall D. Neumaier and H. Kurz

schall@amo.de

AMO GmbH, Otto-Blumenthal-Strasse 25, 52074 Aachen, Germany

146

High frequency transistors, the core of modern information and communication systems, have been recognized from the very beginning as one of the most promising fields of applications for graphene having the potential to significant outperform transistors based on Silicon and III/V semiconductors in terms of speed. This large expectation has mainly been fuelled by grapheneâ&#x20AC;&#x2122;s outstanding charge carrier mobility, the large saturation velocity and the 2D nature giving prospects for ultimately scaled devices.

Although single graphene transistors have already proven these expectations by delivering high cut-off frequencies up to 420GHz [1], the realization of integrated circuits based on graphene transistors is still in its embryonic stage.

To date the most complex integrated circuit based on GFETs are a mixer with one GFET and passive components operating at GHz frequencies [2] and an inverter operating at kHz frequency and consisting of one p and one n type GFET [3]. The realization of more complex circuits containing several GFETs was so far limited by the process technology, which did not allow the highly reproducible fabrication of GFETs with designed properties.

Here we demonstrate the realization of integrated inverters consisting of one n and one p type GFET with record voltage gain AV = 20. The GFETs are based on CVD grown graphene and ambivalent operation was achieved by biasing as previously shown in [3]. High voltage gain has been achieved using a local back-gate geometry (see figure 1c). This unique geometry allows the fabrication of high quality Al2O3 with an EOT of 3 nm, avoiding the rather complex deposition of dielectric layers on-top of the graphene. Inputoutput matching of the operation voltages in

single inverters was realized by proper control of the individual process steps and the thereto related unintentional doping.

Based on such inverters as major building blocks and a highly reproducible process technology, we realized the first graphene based integrated ring oscillator. The ring oscillator consists of 6 n-type and 6 p-type transistors, so that 5 inverters from a loop, while one inverter is needed to decouple the loop from the measurement equipment. An optical micrograph (false color) and a corresponding circuit diagram are shown in figure 1a and 1b, respectively. The fundamental oscillation frequency fOSC of the ring oscillator is ranging from 20 to 30 MHz depending on the supply voltage (figure 2b). This is consistent with the intrinsic parameters of the circuit. The delay time of one inverter is given by Ď&#x201E; = 1/2nfOsc = 3 ns at VDD = -3 V. Taking into account the large parasitic capacitance, which are in our design mainly related to the large overlap between the gate electrode and source and drain, we get an intrinsic delay time of a single inverter of 0.3 ns.

Acknowledgements: This work was financially supported by the German Science Foundation DFG under the project Ultragraphen (BA3788/21) and by the European Commission under the project GRAFOL (285275).

References [1] R. Chen et al., PNAS doi: 10.1073/pnas.1205696109 (2012).

[2] Y.-M. Lin et al., Science 332, 1294 (2011).

[3] L.G. Rizzi et al., NanoLetters 12, 3948 (2012).

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Figures

Figure 1: a) Optical micrograph of an integrated ring oscillator (false color). b) Circuit diagram of the ring oscillator. c) Schematic of a single inverter stage.

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147

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Figure 2: a) Time transient of the output voltage of the ring oscillator. b) Fundamental oscillation frequency of the ring oscillator as a function of the supply voltage.

Oral 1,2

Laser photochemical reduction and doping of graphene oxide for organic electronics

Emmanuel Stratakis 2,3 G. Viskadouros 2,4 E. Koudoumas and E. Kymakis2,4

stratak@iesl.forth.gr

1

Institute of Electronic Structure and Laser, Foundation for Research & Technology Hellas, (IESL-FORTH), P.O. Box 1527, Heraklion 711 10, Greece 2 University of Crete, Heraklion 714 09, Greece.

3 Department of Sciences, Technical University of Crete, GR-73100, Hania, Greece 4 Center of Materials Technology & Photonics,Technological Educational Institute of Crete, Heraklion, 710 04, Crete, Greece.

This paper will present our recent work on the application of laser radiation for the photochemical reduction [1], functionalization and doping of graphene oxide (GO) sheets. In particular, we report on the first reduction technique, compatible with flexible, temperature sensitive substrates, for the production of flexible GO electrodes. It is based on the use of femtosecond laser irradiation for the in-situ, non-thermal, reduction of spin coated GO films on flexible substrates over a large area.

Furthermore, we present a simple photochemical method for the simultaneous reduction and doping of GO sheets through pulsed UV laser irradiation of GO in liquid or gas media. Using this technique Cl and N doping was rapidly carried out at room temperature in only few minutes. Doping is accompanied by simultaneous reduction of GO which decreases oxygen levels from â&#x2C6;ź30% in asprepared GO down to â&#x2C6;ź3% in pulsed laser irradiated GO. Potential applications of pulsed laser synthesized and modified materials in organic electronics, particular to bulk heterojunction organic solar cells and electron emission cathodes are demonstrated and discussed

Figures

References

148

[1] E. Kymakis , K. Savva , M. M. Stylianakis , C. Fotakis , E. Stratakis, Adv. Funct. Mater. 2013, DOI: 10.1002/adfm.201202713.

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Invited Atomic Imaging and spectroscopy of defects in low-dimensional materials

Kazu Suenaga Suenaga-kazu@aist.go.jp

National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba 305-8565 Japan

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point defect by ADF imaging and EELS, and energyloss near edge fine structure (ELNES) is used to investigate the electronic states of nitrogen atoms around the point defect. The work provides an example of spectroscopic imaging based on the scanning transmission electron microscopy (STEM)EELS techniques to demonstrate the possibilities of exploring the electronic states with single atom sensitivity.

A JEM-2100F equipped with a delta corrector and cold field emission gun was operated at 60kV for these spectroscopy experiments [10]. A fast Frourier transform (FFT) of the typical ADF image shows that the microscope can resolve 0.108 nm in the STEM mode. The probe current was ~ 40 pA. In this condition the single atom spectroscopy at the graphene edge becomes feasible and shows distinct properties of edge carbon atoms [11].

Here we will show our recent progress in electron microscopy and its in situ investigations to visualize the various atomic defects in the low-dimensional carbon or non-carbon nanostructures. The monovacancy analysis in h-BN single-layer [12] and the alloying and doping behaviors of MoxW1-xS2 single-layers [13] will be presented.

[1] [2] [3] [4] [5] [6]

A. Hashimoto et al., Nature, 430 (2004) pp.870-873 K. Suenaga et al., Nature Nanotech., 2 (2007) pp.358-360 J. Meyer et al., Nano lett., 8 (2008) pp.3582 C. O. Girit, et al., Science 323, 1705â&#x20AC;&#x201C;1708 (2009).

C. Jin et al., Phys. Rev. Lett., 102, 195505 (2009) J. Meyer et al., Nano Lett., 9, 2683 (2009)

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References

149

Atomic defects or edge structures are important in crystalline materials, and especially in lowdimensional ones, since the interrupted periodicities strongly affect their physical and/or chemical properties. In bulk crystals, electron microscopes have been widely used to examine structural defects such as dislocations and grain boundaries, which are regarded as one- and twodimensional structural defects, respectively. In contrast, individual point defects (zero-dimensional defects such as mono-vacancies, impurity/dopant atoms) were believed to be difficult to investigate, with both atomic sensitivity and atomic resolution required in the analytical techniques employed. In addition, the specimens need to be very thin in order to detect the individual point defects from image contrast in transmission electron microscopy (TEM).

After a monovacancy was first observed by TEM and proved to be stable even in low-dimensional carbon structures [1], studies of point defects in mono-layered materials have become very popular among scientists. Vacancies and topological defects in graphene are commonly examined at atomic level [2, 3, 4]. Defects and edge structures in hexagonal boron nitride (h-BN) are also a hot topic among physicists [5, 6, 7, 8]. Recently, monovacancies have been successfully identified in WS2 nano-ribbons [9].

Here we describe HR-TEM and spatially resolved EELS studies of various single-layered materials with the interrupted periodicities. Atomic defects and edge structures can be unambiguously identified with the elemental assignment. The inevitable delocalization of EELS signals is suggested to practically limit the achievement of using EELS for chemical mapping with atomic resolution. The boron monovacancy (VB) is assigned as a typical

[7] [8] [9] [10] [11] [12] [13]

[14]

N. Alem et al., Phys. Rev. B 80, 155425 (2009) O. Krivanek et al., Nature 464, 571-574 (2010) Z. Liu et al., Naure Commun. 2, 213 (2011).

T. Sasaki et al., J. Electron Microsc. 59, s7â&#x20AC;&#x201C;s13 (2010).

K. Suenaga and M. Koshino, Nature 468, 10881090 (2010).

K. Suenaga, H. Kobayashi, and M. Koshino, Phys. Rev. Lett., 108 075501 (2012).

D. Dumcenco, H. Kobayashi, Z. Liu, Y.-S. Huang and K. Suenaga, Nature Commun. 4 1351 (3013).

The work is partially supported by JST Research Acceleration Programme.

Figures

Figure 1: Cleaved Mo1-xWxS2 specimens with single- to few-layered regions [13]. (a, b, c) Examples of scanning transmission electron microscope annular dark-field images of mixed Mo1-xWxS2 layers (x = 0, 0.2, and 1). x refers to the starting materials. The single-layer regions are marked with white arrows. Scale bars = 3 nm. Note that some regions with less contrast and no periodic structure are the amorphous carbon layers of inevitable contamination during the transfer process.

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Figure 2 Monovacancy in h-BN layer [12]. (a) ADF image shows a monovacacny in a single layer h-BN. Line-spectrum was recorded along the yellow line. (b) Schematic presentation (red: nitrogen, blue: boron) of boron monovacancy. (c) Nitrogen K-edge fine structures extracted from the line-spectrum. Each of three approximately corresponds to the probe positions marked in (b). A prominent prepeak in the nitrogen K-edge can be found at 392 eV in the spectrum recorded at the position 2, i.e., near the boron vacancy site.

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Invited Controlled Synthesis of Heterostructures of 2D Materials

Peter Sutter

psutter@bnl.gov

Brookhaven National Laboratory, Center for Functional Nanomaterials, Upton, USA

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References [1] P. Sutter, J.I. Flege, and E. Sutter, Nat. Mater. 7 (2008), 406.

[2] P. Sutter, J. Lahiri, P. Albrecht, and E. Sutter, ACS Nano 5 (2011) 7303.

[3] P. Sutter, J. Lahiri, P. Zahl, B. Wang, and E. Sutter, Nano Lett. 13 (2013) 276.

[4] P. Sutter, R. Cortes, J. Lahiri, and E. Sutter, Nano Lett. 12 (2012) 4869.

Figures

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Figure 1: 2D materials and their heterostructures. a) Real-time microscopy of large-scale graphene growth on metals (refs. [1,2]); b) Thickness-controlled few-layer h-BN integrated with graphene (ref. [3]); c) Single layer graphene-boron nitride heterostructures with atomically sharp line interfaces (ref. [4]).

151

Two-dimensional (2D) crystals, such as graphene, hexagonal boron nitride, and a family of metal dichalcogenides, represent a new class of functional materials with a wealth of interesting physical and chemical properties. Going beyond homogeneous 2D crystals, heterostructures that combine different 2D materials in layer stacks or as several tightly interfaced components in a single, atomically thin membrane promise tunable properties and greatly extended functionality, and raise fundamental questions on interface formation, intermixing, strain, polarity, etc., in a new context at reduced dimensionality.

While initial studies on these systems rely on monolayer sheets isolated from layered bulk crystals, broader fundamental investigations and potential applications require reliable and scalable methods for fabricating and processing highquality 2D heterostructures. I will discuss recent advances in understanding the synthesis and processing of heterostructures of 2D materials on metal substrates, derived primarily from real-time observations by surface electron microscopy complemented by high-resolution scanning probe microscopy and in-situ spectroscopy methods.

Focusing on the integration of graphene [1] with hexagonal boron nitride [2], I will discuss pathways to the successful realization of key challenges in the controlled formation of heterostructures: atomically precise thickness and stacking control in superlattices [3] and the creation of atomically sharp line interfaces in heterogeneous single layer membranes [4]. Our combined findings establish a powerful toolset for the scalable fabrication of 2D heterostructures for research and applications.

Oral Applications based on graphene on hexagonal and cubic silicon carbide

Mikael Syväjärvi T. Iakimov J. Nilsson and R. Yakimova

mikael.syvajarvi@graphensic.com Graphensic AB, Mjärdevi Science Park, Teknikringen 7, SE-58330 Linköping, Sweden www.graphensic.com

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There is an intense research in graphene on silicon carbide to explore the properties of monolayer, bilayer, or multilayer graphene on the silicon or carbon face of silicon carbide.

The monolayer graphene with a buffer layer has shown an astounding performance in metrology. In fact, graphene on silicon carbide provides a several orders of magnitude better precision resistance standard in quantum Hall measurements that relates the Planck’s constant, h, and the electron charge, e, than the current one based on gallium arsenide [1].

The graphene and silicon carbide can create a viable platform, for example by a monolithic transistor that uses the entire material system epitaxial graphene on silicon carbide [2]. This was shown to have an on/off ratio exceeding 104 and no damping at megahertz frequencies. The fabrication process requires, in the most simple realization, only one lithography step to build transistors, diodes, resistors and eventually integrated circuits without the need of metallic interconnects.

An issue in graphene is the lack of bandgap.

Ribbons of graphene have shown a potential to create a bandgap of 0.5 eV [3]. The ribbons were created by forced topographical changes on SiC that produced narrow ribbons. This demonstrates the advantage of silicon carbide as an active substrate that creates graphene-substrate interactions to alter the properties of graphene to a metalsemiconducting transition.

Long spin relaxation times, up to 2.3 ns, in monolayer graphene have been shown, while the spin diffusion coefficient is strongly reduced compared to typical results on exfoliated graphene.

The increase of spin relaxation times is probably related to the changed substrate, while the cause

for the small value of spin diffusion coefficient remains to clarify [4].

Still there is room for a broad range of research. For example, the sensitivity to individual molecules opens a research area in biosensors in addition to those of electronics. A high surface to volume ratio and tunable electron transport properties due to quantum confinement effects strongly influence the electrical properties of graphene channels even by minor perturbations, such as molecules on the graphene surface. The biosensors work on the principle of a target disease biomarker that provides a change in the surface charge density [5].

This change can be detected as an electrical signal from the biosensor device. Both SiC and graphene have excellent biocompatibility with in vivo and in vitro studies showing no cytotoxicity responses.

This field includes development of miniaturized systems for detection of disease biomarkers for use in the early diagnosis and monitoring of diseases.

Graphene has also shown to promote GaAs nanowire growth. Due to a self-catalyzed growth technique used, the nanowires were found to have a regular hexagonal cross-sectional shape, and are uniform in length and diameter. Epitaxial growth of a broad range of semiconductors on graphene can in principle be achieved by utilizing a reduced contact area of nanowires. The model is experimentally verified by demonstrating the growth of vertically aligned GaAs nanowires on graphite and few-layer graphene, including graphene on SiC [6].

Most work has been developed on hexagonal silicon carbide. An open research area is graphene on cubic silicon carbide. The commercial polytypes have the hexagonal structure. In our lab we study growth of cubic silicon carbide bulk material, and process graphene on the substrates. In fact, the

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cubic silicon carbide seems to have a process window that allows monolayer graphene [7] in at least similar quality as when using hexagonal silicon carbide. Large homogeneous areas of graphene monolayers (over 50 x 50 μm2) have been grown on 3C-SiC (111) substrates. Differences in the morphology of the graphene layers on different SiC polytypes is related mainly to the minimization of the terrace surface energy during the step bunching process. The uniformity of silicon sublimation is a decisive factor for obtaining large area homogenous graphene. A lower substrate surface roughness results in more uniform step bunching with a lower distribution of step heights and consequently better quality of the grown graphene.

Figures

Figure 1: Silicon carbide wafers are used for large area graphene growth.

References

ImagineNano2013

Figure 3: Low-energy electron microscopy images of 6H (left) and 3C (right), both showing large domains (>50 μm) and dominating monolayer graphene with dark areas of bilayer graphene. Images: Alexei Zakharov, MaxLab.

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Figure 2: Cubic silicon carbide is a polytype that can further explore the graphene on silicon carbide properties.

153

[1] A. Tzalenchuk, S. Lara-Avila, A. Kalaboukhov, S. Paolillo, M. Syväjärvi, R. Yakimova, O. Ka akova, T. J. B. M. Janssen, V. Fal’ko and S. Kubatkin, Nature Nanotech 5 (2010) 186.

[2] S. Hertel, D. Waldmann, J. Jobst, A. Albert, M. Albrecht, S. Reshanov, A. Schöner, M. Krieger and H.B. Weber, Nature Communications 3 (2012) 957.

[3] J. Hicks, A. Tejeda, A. Taleb-Ibrahimi, M. S. Nevius, F. Wang, K. Shepperd, J. Palmer, F. Bertran, P. Le Fèvre, J. Kunc, W. A. de Heer, C. Berger and E. H. Conrad, Nature Physics 9 (2013) 49.

[4] Thomas Maassen, J. Jasper van den Berg, Natasja IJbema, Felix Fromm, Thomas Seyller, Rositza Yakimova, and Bart J. van Wees, Nano Lett. 12 (2012) 1498.

[5] Guy, O.J. Burwell, G.; Tehrani, Z.; Castaing, A.; Walker, K.-A.; Doak, S.H., Materials Science Forum 711 (2012) 246.

[6] A. Mazid Munshi, Dasa L. Dheeraj, Vidar T. Fauske, Dong-Chul Kim, Antonius T. J. van Helvoort, Bjørn-Ove Fimland, and Helge Weman, Nano Lett. 12 (2012) 4570.

[7] G. Reza Yazdi, Remigijus Vasiliauskas, Tihomir Iakimov, Alexei Zakharov, Mikael Syväjärvi, Rositza Yakimova, Carbon, in press (2013).

Invited Graphene Synthesis, Transfer, FETs and Scaling

1

Kenneth Teo 2 2 L. Tao , J. Lee 2 3 D. Akinwande , K. Celebi H. G. Park3, Jie Sun4 5 T. Booth and 5 P. Boggild

1

Nalin Rupesinghe, Andy Newham, Paul Greenwood, Matthew Cole AIXTRON, Cambridge, United Kingdom 2 University of Texas at Austin, USA 3 ETH Zurich, Zurich, Switzerland 4 Chalmers University of Technology, Sweden 5 Technical University of Denmark, Denmark

k.teo@aixtron.com

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Growth and characterization of graphene grown using copper foils as well as copper films on silicon dioxide on silicon substrates were performed.

Kinetics of growth and effective activation energy for the graphene synthesis will be discussed for the surface catalytic synthesis of graphene. Conditions for large-scale synthesis of monolayer graphene will be addressed in this talk. Wafer-scale graphene transfer and electrical results will be presented. Based on our preliminary results from capped 100-mm wafer scale graphene transistors, we expect a mobility of 4-6 k cm2/Vs with symmetry hole/electron transport. In addition, important circuit blocks such as frequency multipliers and amplifiers with gain of about five have been achieved. Integrating the CVD graphene with Si VLSI chips affords interconnects and gas sensors that utilize the resistance modulation of graphene. Likewise, graphene integrated onto flexible sheets yield 25GHz cutoff frequency and robust performance down to 0.7mm bending radius which represents the state of the art for graphene nanoelectronics on soft substrates. Key considerations and challenges for scaling are discussed and results for graphene growth on the 300mm wafer scale will be discussed.

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Oral Secondary Hot-Carrier Generation in Graphene 1

ICFO – Institut de Ciéncies Fotóniques, Mediterranean Technology Park, Castelldefels (Barcelona) 08860, Spain 2 Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 3 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA 4 Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany 5 FOM Institute AMOLF, Amsterdam, Science Park 104, 1098 XG Amsterdam, Netherlands 6 Graphenea SA, 20018 Donostia-San Sebastián, Spain

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klaas-jan.tielrooij@icfo.es

follow the ensuing energy relaxation dynamics. We show experimentally, in combination with theoretical modeling, that carrier-carrier scattering is the dominant relaxation process. This process leads to the creation of secondary hot electrons that originate from the conduction band, a process we refer to as “hot-carrier multiplication”. Since hot electrons in graphene can drive currents, multiple hot carrier generation makes graphene a promising material for highly efficient broadband extraction of light energy into electronic degrees of freedom, enabling high-efficiency optoelectronic applications.

[1] F. Bonaccorso, Z. Sun, T. Hasan, And A.C. Ferrari, “Graphene photonics and optoelectronics,” Nature Phot. 4, 611-622 (2010).

[2] T. Win er, A. Knorr and E. Malic, “Carrier multiplication in graphene,” Nanolett. 10, 4839-4843 (2010).

[3] N.M. Gabor et al, “Hot carrier-assisted intrinsic photoresponse in grapheme,” Science 334, 648-652 (2011).

[4] K.J. Tielrooij et al, “Photoexcitation Cascade and Multiple Hot Carrier Generation in Graphene”, Arxiv:1210.1205, accepted for publication in Nature Physics.

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References

155

For many optoelectronic applications, such as photodetection and light harvesting, it is highly desirable to identify materials in which an absorbed photon is efficiently converted to electronic excitations. The unique properties of graphene, such as its gapless band structure, flat absorption spectrum and strong electron-electron interactions, make it a highly promising material for efficient broadband photon-electron conversion [1]. Indeed, recent theoretical work has anticipated that in graphene multiple electronhole pairs can be created from a single absorbed photon during energy relaxation of the primary photoexcited e-h pair [2]. A photoexcited carrier relaxes initially trough two competing pathways: carrier-carrier scattering and phonon emission. In the former process the energy of photoexcited carriers remains in the electron system, being transferred to secondary electrons that gain energy (become hot), whereas in the phonon emission process the energy is lost to the lattice as heat. While recent experiments have shown that photoexcitation of graphene can generate hot carriers [3], it remains unknown how efficient this process is with respect to optical phonon emission.

In this talk we discuss the energy relaxation process of the primary photoexcited e-h pair in doped single-layer graphene [4]. In particular, we quantify the branching ratio between the two competing relaxation pathways. Given the challenging timescale with which these processes occur, we employ an ultrafast Optical pump – Terahertz probe measurement technique, where we exploit the variation of the photon energy of the pump light. Changing this photon energy is crucial as it allows us to prepare the system with photoexcited carriers having a prescribed initial energy determined by the photon energy, and

1

Klaas-Jan Tielrooij 2,3 4,5 J.C.W. Song , S.A. Jensen 6 6 A. Centeno , A. Pesquera A. Zurutuza Elorza6 4 2 M. Bonn , L.S. Levitov 1 and F.H.L. Koppens

Oral Inkjet-printed 2d crystals

Felice Torrisi T. Hasan F. Bonaccorso and A. C. Ferrari

Cambridge Graphene Centre, Department of Engineering, University of Cambridge, 9 J.J. Thomson Avenue CB3 0FA, Cambridge, UK

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Ink-jet printing is one of the most promising techniques for large area fabrication of flexible electronic devices [1,2]. Despite much progress, ink-jet printed organic Thin Film Transistor (TFT) still show poor air stability, limited lifetime [3], mobility (Îź<0.5 cm2 V-1 s-1) [3], and ON/OFF ratios(<105). Near-ballistic transport and high mobility, make graphene an ideal material for nanoelectronics [6]. Its optical and mechanical properties are ideal for thin-film transistors and transparent and conductive electrodes [7].

Two-dimensional (2d) crystals offer properties that are complementary to, yet distinct, from those in graphene. Several semi-conducting 2d crystals show a transition from an indirect band-gap in the bulk to a direct gap in the monolayer. For example, in Molybdenum Disulfide (MoS2) the bulk indirect bandgap of 1.3 eV increases to a direct bandgap of 1.8 eV in single-layer [9], promising interesting new FET [10] and optoelectronic devices [11,12].

Here we prepare graphene, MoS2 inks (Figure 1a) and exploit the properties of MoS 2 to fabricate inkjet-printed MoS2-based TFTs (Figure 2a) and graphene/MoS2 heterostructures. High quality MoS2 flakes are dispersed in organic solvents by ultrasonication followed by ultracentrifugation [13] to remove large fragments that are likely to clog the nozzle of the ink-jet printer. We investigate MoS2 exfoliation in Isopropanol, 1Methyl-2-pyrrolidone, Dimethylformamide as well as two solvents mixtures. By Optical Absorption Spectroscopy, Transmission electron microscopy and Raman spectroscopy we find that Water/Ethanol mixture gives the highest yield of MoS2 single layers. MoS2-ink stripes are then inkjet-printed on Si/SiO2. The electrical and optical performances of our devices, demonstrate the viability of 2d-crystals printable inks.

ft242@cam.ac.uk

References [1] [2] [3] [4] [5]

H. Sirringhaus et al. Science, 290 (2000) 2123.

B. J. DeGans et al. Adv. Mater. 16 (2004) 203.

M. Singh et al. Adv. Mater. 22 (2010) 673.

M. Ha et al. ACS Nano 4 (2010) 4388. ] P. Beecher et al. J. Appl. Phys. 102 (2007) 043710.

[6] A. K. Geim et al. Nat. Mater. 6 (2007) 183.

[7] F. Bonaccorso et al. Nat. Photon. 4 (2010) 611.

[8] F. Torrisi et al., ACS Nano, 6, (2011) 2992.

[9] T. Li, J. Phys. Chem. 111, (2007) 16129.

[10] B. Radisavljevic, Nat. Nano., 6 (2011) 147.

[11] K. F. Mak, Nat Nano., 7, (2012) 494.

[12] R. S. Sundaram et al., arXiv:1211.4311, (2012).

[13] J. Coleman et al., Science, 331, (2011) 6017.

Figures

Figure 1: a) Graphene-ink (left), MoS2-ink, Boron Niride-ink. b) Example of graphene ink-jet printed pattern.

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Keynote Graphene spintrocics: The current state of the art

Bart van Wees b.j.van.wees@rug.nl

Zernike Institute of Advanced Materials Nijenborgh 4.13 University of Groningen 9700 AB Groningen The Nentherlands

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and theory, will address the science and technology of graphene spintronics in various systems, working towards future applications.

[1] N. Tombros, C. Józsa, M. Popinciuc, H. T. Jonkman & B. J. van Wees, "Electronic spin transport and spin precession in single graphene layers at room temperature", Nature 448, 571-574 (2007).

[2] P. J. Zomer, M. H. D. Guimarães, N. Tombros, B. J. van Wees, "Long Distance Spin Transport in High Mobility Graphene on Hexagonal Boron Nitride", Phys. Rev. B 86, 161416(R) (2012).

[3] M. H. D. Guimarães, A. Veligura, P. J. Zomer, T. Maassen, I. J. Vera-Marun, N. Tombros, and B. J. van Wees, "Spin Transport in High-Quality Suspended Graphene Devices", Nano Letters 12 (7), 3512-3517 (2012).

[4] M. Wojtaszek, I. J. Vera-Marun, T. Maassen, B. J. van Wees, "Enhancement of spin relaxation time in hydrogenated graphene spin valve devices", Phys. Rev. B: Rap. Comm. 87, 081402(R) (2013).

[5] R. R. Nair et al., “Spin-half paramagnetism in graphene induced by point defects” Nature Physics 8, 199–202 (2012).

[6] K.M. McCreary et al., “Magnetic moment formation in graphene detected by scattering of pure spin currents,”Phys. Rev. Lett. 109 , 186604 (2012).

[7] B. Dlubak et al., “Highly efficient spin tranposrt in epitaxial graphene on SiC”, Nat. Phys. 557 (2012).

[8] T. Maassen, J. J. van den Berg, E. H. Huisman, H. Dijkstra, F. Fromm, T. Seyller, B. J. van Wees, "Localized States Influence Spin Transport in Epitaxial Graphene", Phys. Rev. Lett. 110, 067209 (2013).

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References

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I will give an overview of the current state of the physics and technology of graphene spintronics. I will explain the basic concepts of spin accumulation, spin transport, spin precession, spin manipulation and spin relaxation. It will be shown how various types of measurements (two, three and four terminal geometries) can be used to extract the spin transport parameters in graphene, such as spin relaxation length and spin relaxation time. The various mechanisms responsible for spin relaxation in graphene (Elliott Yafet vs. Dyakonov Perel) will be discussed, and how they depend on the graphene quality and mobility. I will present results obtained on various graphene substrates (with SiO2 as reference [1]), such as boron nitride [2], and graphene grown on the C and Si face of silicon carbide [7,8]. Also suspended graphene has been used to optimize the spintronics properties of graphene [3].

I will discuss that the ultimate potential of graphene for spintronics has not yet been established, and that the current record of 7 micrometer for the room temperature spin relaxation length is expected to be broken soon. A connection with (para [5] and (possibly) ferro) magnetism in graphene will be made, discussing recent measurements [4,6] which have shown that magnetic moments can be induced in graphene, which can be studied in detail by their effect on spin transport. The potential of spin transport for detecting (localized) spins which are present above or below the graphene will be addressed [7].

Finally I will present a roadmap for future planned developments in science and technology of graphene spintronics, based on the for the graphene workpackage in the EU Graphene Flagship. It will be shown how the spintronics workpackage, by a concerted effort of experiment

Invited Electronic structure of graphene mono and multilayers on SiC probed by STM 1

Institut Néel, CNRS-UJF, Boîte Postale 166, F-38042 Grenoble, France Dept. Física de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid, Spain 3 LPTM, Université de Cergy-Pontoise-CNRS, F-95302 Cergy-Pontoise, France 2

158

Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) are efficient probes of the electronic structure of supported graphene layers.

Besides revealing intrinsic properties of graphene, these techniques can be used to probe the interaction between the graphene surface layer and the supporting material. We shall present examples related to our recent works on the electronic structure of graphene mono and multilayers grown on hexagonal SiC substrates. We shall first briefly discuss the role of the pseudo-spin in quasiparticle interference patterns detected by STM [1] and the analysis of the stacking dependence of the interaction between graphene and localized levels [2].

The presentation will then focus on an appealing route for modifying graphene’s band structure by exploiting a rotation between stacked graphene layers [3]. Theory suggests that the interlayer interaction strongly impacts the band structure of the twisted layers for rotation angles  smaller than 15°: the band velocity is reduced [3, 4] and low energy van Hove singularities (vHs) appear in the density of states (DOS) [5]. Their energy decrease with decreasing  and they converge towards the Dirac point for low  values (<1°) where weakly dispersive bands develop at low energy. The electronic structure of twisted bilayer graphene is thus expected to be tunable using the rotation angle  as a control parameter.

We will present an STM/STS study complemented by ab-initio and tight binding calculations, of the local DOS (LDOS) of twisted layers grown on the 6H-SiC(000-1) face. Our experimental and theoretical data [6] show that vHs exist in a wide range of rotation angles (1°<<10°), and that they are robust against perturbations (stacking sequence, layer corrugation) to the ideal model

1

Jean-Yves Veuillen

I. Brihuega2, P. Mallet1 H. González-Herrero2 G. Trambly de Laissardière3 M. M. Ugeda2, L. Magaud1 J.M. Gómez-Rodríguez2 F. Hiebel1 and F. Ynduráin2

jean-yves.veuillen@grenoble.cnrs.fr

usually considered by theory. These results are consistent with previous measurements made in a smaller  range on samples prepared on other substrates [5], which establishes the intrinsic character of the rotation-induced features. A simple data analysis gives directly the value of the interlayer coupling parameter [6].

References [1] P. Mallet, I. Brihuega, S. Bose, M. M. Ugeda, J. M. Gomez-Rodriguez, K. Kern and J. Y. Veuillen, Phys. Rev. B 86 (2012) 045444.

[2] F. Hiebel, P. Mallet, J.-Y. Veuillen, and L. Magaud, Phys. Rev. B 86 (2012) 205421.

[3] J. M. B. Lopes dos Santos, N. M. R. Peres, and A. H. Castro Neto, Phys. Rev. Lett., 99 (2007) 256802.

[4] G. Trambly de Laissardière, D. Mayou, and L. Magaud, Nano Lett., 10 (2010) 804.

[5] G. Li, A. Luican, J. M. B. Lopez dos Santos, A. H. Castro Neto, A. Reina, J. Kong and E. Andrei, Nat. Phys., 6 (2010) 109.

[6] I. Brihuega, P. Mallet, H. González-Herrero, G. Trambly de Laissardière, M. M. Ugeda, L. Magaud, J.M. Gómez-Rodríguez, F. Ynduráin, and J.-Y. Veuillen, Phys. Rev. Lett., 109 (2012) 196802.

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Figures

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Figure 1: a) vHs (arrows) in the LDOS of twisted layers (with =3.3°) measured by STS. b) Splitting of the vHs as a function of  (dots from [6], squares from [5]).

Oral Electronic structure of graphene hybrid systems: Screening and interactions

1

Tim Wehling 1 M. Rösner 1 M. Schüler A. Lichtenstein3 3 S. Yuan and 2 M. Katsnelson

1

Institute for Theoretical Physics and BCCMS, University of Bremen, D-28359 Bremen Germany 2 1st Institute for Theoretical Physics, University of Hamburg, D-20355 Hamburg, Germany 3 Radboud University Nijmegen, NL-6525 AJ Nijmegen, The Netherlands

We consider the effect of adsorbates and substrates on the electronic screening and electron-electron interactions in graphene. First, resonant scatterers such as hydrogen adatoms can strongly enhance the low-energy density of states in graphene. We study the impact of these impurities on electronic screenin and find a twofaced behavior: Kubo formula calculations reveal an increased dielectric function ε upon creation of midgap states but no metallic divergence of the static ε at small momentum transfer q→0. This bad metal behavior manifests also in the dynamic polarization function and can be directly measured by means of electron energy loss spectroscopy. A new length scale lc beyond which screening is suppressed emerges, which we identify with the Anderson localization length [1].

We then address the question of how strong Coulomb interactions in graphene derived materials are: Free standing graphene is shown to feature simultaneously strong local (U/t~3.3) and non-local Coulomb interaction terms [2]. Based on the Peierls-Feynman-Bogoliubov variational principle we show that the non-local Coulomb interactions can effectively screen the local interactions and stabilize the Dirac electron sea in graphene [3]. Interestingly, the ratio of the local to the non-local Coulomb interaction can be controlled by a metallic substrate, which efficiently screens non-local Coulomb terms.

wehling@itp.uni-bremen.de

[2] T. Wehling, E. Şaşıoğlu, C. Friedrich, A. Lichtenstein, M. Katsnelson, and S. Blügel, Phys. Rev. Lett. 106, 236805 (2011).

[3] M. Schüler, M. Rösner, T. Wehling, A. Lichtenstein, M. Katsnelson, arXiv:1302.1437 (2013).

Figures

Figure 1: Effective Coulomb interactions in graphene: Contribution to the static dielectric function in graphene due to the σ-bands, which controls the effective interactions strength of the πelectrons. From [2].

References

160

[1] S. Yuan, T. Wehling, A. I. Lichtenstein, and M. I. Katsnelson, Phys. Rev. Lett. 109, 156601 (2012).

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Oral Chemical Potential of Inhomogeneous Single Layer of Graphene

Department of Electrical Engineering, Technion, Haifa, Israel, 32000 Russell Berrie Nanotechnology Institute, Technion, Haifa, Israel, 32000

yuvaly@ee.technion.ac.il

Many of the unique electrical properties of single layer of graphene (SLG) have been attributed to its zero band gap linear dispersion relation and linear density of state (DOS). Several experiments were conducted on SLG and indeed found the predicted non interacting DOS with small correction to the graphene inverse compressibility due to electronelectron interaction. In most of these studies the basic technique is based on measuring the change in the graphene chemical potential, δµ under periodic modulation of the gate bias, δVg, which is responsible to the change in the hole carrier density, δp, for example. Since the DOS, as well as the compressibility, are given by , δp is usually extracted either from the

of negligible fraction of minority carrier within the same puddle of majority carrier is well justified.

Alternatively, it is possible to measure directly the chemical potential, and derive from it the inverse compressibility and the DOS. For gated p-type graphene far from the CNP the relation between the external voltage and its chemical potential is given by

gate bias, or Hall data. However, as the system is tuned towards the Dirac point, the graphene layer is brake into puddles, were electrons (n) and holes (p) coexist. Moreover, since µ is not a linear function of the carrier density, the gate bias induces non equal changes of the electrons and holes densities. As a consequence, for those experiments that measured directly the quantum capacitance which is proportional to the compressibility, the density assignment is inadequate in the nonhomogeneous regime. Thus, these two mentioned obstacles may lead to non accurate estimation of the electronelectron exchange and correlation contributions, which are of significant physical importance due to their many body origin.

A common method to extract the densities of p and n are based on two band model for the Hall effect.

However, this method in the inhomogeneous regime is inadequate. The reason for that is because this model for Hall effect was derived when these two carriers share the same region in space. However, for the graphene, this is not the case. Although electrons and holes near the charge neutrality point (CNP) coexist, at zero temperature they never share the same region in space. As will become evident later on in this study, the disorder potential strength is ≈100 meV, thus even at room temperature our assumptions

small contribution to Eq. 1, which makes measurements of the DOS challenging. However, if one increases dramatically cg, either by thinner oxide layer, or using high dielectric material, or both, the quantum term will no longer be negligible. In Fig. 1a we depict the relative contribution of the geometric and quantum terms with respect to the total energy (eVg) as function of carrier density, for two extreme cases. The first, plotted as light blue (cg) and magenta (cq) reects the relative contributions for 300nm SiO2 gate oxide where the quantum part is negligible. The second case (blue and red) presents the same two relative contribution for 2 nm of HfO2 with dielectric constant of ε = 15, which was one of the gate oxide that we have used in this study. Clearly one can see that for densities lower than 2 x 1012 cm-2 the quantum term is more than 50% of the total energy, and drops slowly to ~30% with increasing densities up to 1013 cm-2.

In this study [1] we prepare few kinds of devices, all comprise of single layer of graphene (SLG) on top of highly p-doped silicon substrates with thin oxide layer, of 2 and 15nm HfO2, 10nm SiO2, and 50 and 100nm Si3N4. Typical transfer characteristics are presented in Fig. 1b. Many of these devices have high transconductance (gm = I= Vg=W, where W is the device width) and the highest gm we have measured at

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where cg is the geometric gate-graphene capacitance per unit area, and φ0 is the electrical potential attributed to residual doping. Usually, the geometric capacitance is much smaller than the quantum capacitance, cq = e2 ,, and the chemical potential is

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2

161

1

1

Yuval E. Yaish 1,2 E. M. Hajaj 1 O. Shtempluk V. Kochetkov1 and 1 A. Razin

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room temperature and ambient conditions was 700 µS/µm at VDS = 1V. After subtracting its contact resistance one finds gm ≈ 11mS=µm, which to the best of our knowledge, is the highest transconductance ever measured in SLG. The normalized gm, that takes into account the geometrical dimension of the device as well as the bias voltage in which the measurements were done is given by gmN = Lgm/VDS = µcg [2], and found to be 2.8=44mFV-1s-1 w/wo contact resistance.

From direct measurements of the mobility, using Hall effect, one obtains that cg = 1.6 .1 µFcm-2, which is in good agreement with the expected theoretical value of 1.7 µFcm-2. This gate capacitance is 130 times larger than the usual 285 nm SiO2 based capacitor, and the largest capacitance that were published to date in SLG. In the limit of homogenous graphene, p-type for example, the carrier density is measured by the Hall effect, and 2 µ(p) is found from Eq. 1. However, as the density decreases, puddles forms, and the densities are unknown. In a recent paper Li et al. [3] developed a theoretical model for transport in inhomogeneous graphene. They introduced single parameter, s, which described the standard deviation of the electrostatic potential uctuations of the graphene landscape according to gaussian distribution. As a consequence, the density of states of both electrons and holes become finite at the Dirac point and electrical transport may prevail. This model also predicts the temperature dependence of the carrier densities, chemical potential, and their total conductivity according to effective-medium theory of conductance in composite mixtures [4]. Thus, incorporating their model, with generalization of Eq. 1 for the two types of charge carriers, as well as with our conductivity data, allow us to solve self consistently these set of equations and extract the uctuation parameter, s, the charge carriers densities, the chemical potential, and the inverse compressibility.

The results of such analysis are plotted in Fig. 2a, and b before (inset) and after (main) annealing for the ptype brunch. Similar results were found as well for the n-type branch. The red curve in Fig. 2a presents the experimental data and the blue line the expected theoretical result. As evident, the agreement is very good, and at low densitieswhere electron and hole puddles coexist, the chemical potential and the inverse compressibility have been modifed due to the electrostatic disorder potential, that may be well described by gaussian disorder distribution.

In addition, from our measurements and analysis we extract the temperature dependence of the charge carriers densities, the sheet resistance, ρ, and the disorder strength parameter, s. Surprisingly, unlike many theoretical and experimental studies, we found

non monotonous temperature behavior of ρ which is mainely attributed to the temperature dependence of s. By extracting the electron and holes densities one can delineate their T dependence from the overall ρ (T), one can accurately study the temperature dependence of the dierent scattering mechanisms that affect the resistivity of single layer graphene.

References [1] E. M. Hajaj, O. Shtempluk, A. Razin, V. Kochetkov, and E. Y. Yaish, submitted to Phys. Rev. B, 2013.

[2] Huilong Xu, Zhiyong Zhang, Haitao Xu, Zhenxing Wang, Sheng Wang, and Lian-Mao Peng, Acs Nano, 5:5031{5037, 2011.

[3] Qiuzi Li, E. H. Hwang, and S. Das Sarma, Phys. Rev. B, 84, 2011.

[4] S. Kirkpatrick, Rev. Mod. Phys., 45:574{588, 1973.

Figures

Figure 1: Color online) (a) Relative energy contribution with respect to carrier density according to Eq. 1 calculated at zero temperature and 0 = 0. (b) Sheet conductance (G□) vs gate voltage for three different substrates.

Figure 2: (Color online) (a) Chemical potential and (b) inverse compressibility vs hole densities before (inset) and after (main) annealing.

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Invited Polycrystalline graphene: atomic structure and electronic transport properties

Oleg V. Yazyev

oleg.yazyev@epfl.ch

Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH1015 Lausanne, Switzerland

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backscattering involving localized electronic states of topological origin [6].

These results demonstrate that dislocations and grain boundaries are intrinsic topological defects which dramatically affect the transport properties of graphene and can also be used for engineering novel functional devices [7].

References [1] P. Y. Huang, C. S. Ruiz-Vargas, A. M. van der Zande, W. S. Whitney, M. P. Levendorf, J. W. Kevek, S. Garg, J. S. Alden, C. J. Hustedt, Y. Zhu, J. Park, P. L. McEuen and D. A. Muller, Nature, 469 (2011) 389.

[2] K. Kim, Z. Lee, W. Regan, C. Kisielowski, M. F. Crommie and A. Zettl, ACS Nano, 5 (2011) 2142.

[3] J. An, E. Voelkl, J. W. Suk, X. Li, C. W. Magnuson, L. Fu, P. Tiemeijer, M. Bischoff, B. Freitag, E. Popova and R. S. Ruoff, ACS Nano, 5 (2011) 2433.

[4] O. V. Yazyev and S. G. Louie, Phys. Rev. B, 81 (2010) 195420.

[5] O. V. Yazyev and S. G. Louie, Nature Mater. 9 (2010) 806.

[6] F. Gargiulo and O. V. Yazyev, submitted.

[7] J.-H. Chen, G. Autès, N. Alem, F. Gargiulo, A. Gautam, M. Linck, C. Kisielowski, O. V. Yazyev, S. G. Louie, and A. Zettl, submitted.

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There is growing evidence of the polycrystalline nature of graphene samples at micrometer length scales [1-3]. Grain boundaries and dislocations, intrinsic topological defects of polycrystalline materials, inevitably affect all kinds of physical properties of graphene. This talk reviews our theoretical efforts directed towards understanding the atomic structure and electronic transport properties of polycrystalline graphene. Recent experimental works on this subject are also covered in the presentation.

In the first part of my talk, I will introduce a general approach for constructing dislocations in graphene characterized by arbitrary Burgers vectors and grain boundaries covering the complete range of possible misorientation angles [4]. By means of first-principles calculations we address the thermodynamic properties of grain boundaries revealing energetically favorable largeangle configurations as well as dramatic stabilization of small-angle configurations via the out-of-plane deformation, a remarkable feature of graphene as a two-dimensional material.

The rest of my talk will cover on the electronic transport properties of polycrystalline graphene focusing on the following two scenarios. Ballistic charge-carrier transmission across the periodic grain boundaries is shown to be governed primarily by a simple momentum conservation law [5]. Two distinct transport behaviors are predicted − either perfect reflection or high transparency with respect to low-energy charge carriers depending on the grain boundary periodicity.

Beyond the momentum conservation picture we find that the transmission of low-energy charge carriers can be dramatically suppressed in the small-angle limit. This counter-intuitive behavior is explained from the standpoint of resonant

Invited A quantum spin Hall effect in monolayer graphene without time reversal symmetry

Andrea Young

MIT (USA)

The quantum spin Hall (QSH) effect [1] is a two dimensional electronic phase characterized by an excitation gap in the bulk but gapless, helical boundary states. Since its original discovery in HgCdTe quantum wells [2], the QSH effect has become nearly synonymous with the time-reversal invariant two dimensional topological insulator. I will describe recent experiments in which we demonstrate a QSH effect without time reversal symmetry, realized by exploiting the particle-hole symmetry of the anomalous Landau level in monolayer graphene [3]. Using large in-plane magnetic fields, we drive a transition from a spinunpolarized insulating phase to a spin-polarized metallic phase with ~2e2/h conductance, in which we observe the nonlocal transport signatures of the QSHE. Simultaneous capacitance measurements, which probe the bulk, show that throughout the transition and into the QSH regime, the bulk gap never closes, in contravention of expectations in the more familiar, time reversal invariant case where the QSH represents a topologically distinct phase of matter. The transition itself occurs via an intermediate canted antiferromagnetic state [4], which hosts gapped, partially helical edge states that have no analog in topological insulators.

[3] Abanin, D. A., Lee, P. A. & Levitov, L. S. Phys.

Rev. Lett. 96, 176803 (2006); Fertig, H. A. & Brey, L. Phys. Rev. Lett. 97, 116805 (2006).

[4] Kharitonov, M. Phys. Rev. B 85, 155439 (2012); Kharitonov, M. Phys. Rev. B 86, 075450 (2012).

References

164

[1] Kane, C. L. & Mele, E. J. Phys. Rev. Lett. 95, 226801 (2005).

[2] Bernevig, B. A., Hughes, T. L. & Zhang, S.-C. Science 314, 1757-1761 (2006); Konig, M. et al. Science 318, 766-770 (2007).

ImagineNano2013

Oral Controllable synthesis of large monolayer and multilayer graphene crystals

1

Shou-En Zhu 2 V. E. Calado 2 L. M.K. Vandersypen and G.C.A.M. Janssen1

Shouen.zhu@tudelft.nl 1

Micro and Nano Engineering Laboratory, Precision and Microsystems Engineering, Delft University of Technology, 2628 CD Delft, The Netherlands 2 Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands

ImagineNano2013

References [1] Thiti Taychatanapat et al. Electrically tunable transverse magnetic focusing in graphene.

Nature Physics, 2013, in press.

Figures

Figure 2: Hexagonal CVD multilayer graphene transfer onto SiO2 substrate.

GRAPHENE 2013

Figure 1: Transverse magnetic focusing measurement in monolayer graphene at 4K.

165

Chemical vapor deposition (CVD) synthesis of monolayer graphene on copper foil has been intensively studied during last few years. In order to match or exceed the quality of exfoliated graphene, the most important strategies are to make the graphene domains as large as possible and to prevent charge scattering from the substrate.

Here we report a controllable and scalable method (with well-defined conditions in a homemade CVD furnace) to achieve graphene single layer crystals over 500 Îźm in diameter. The nucleation density was reduced to less than 1 per square millimeter, and shape of graphene crystals is analogous to hexagonal snow crystals. Transport measurement of single layer CVD graphene on a boron nitride substrate at 4K shows mobility up to 50,000 cm2/Vs. Furthermore, magnetic focusing between neighboring contacts has been observed as shown in Fig. 1, which demonstrates ballistic transport up to 1 um for the first time in CVD graphene [1].

These measurements demonstrate a promising potential of CVD graphene for fundamental physics research.

The growth of bi-and trilayer graphene over 30 um is also reported. The outline of the second and third layer is almost a perfect hexagon as shown in Fig. 2. The interaction between the various layers in the graphene and the interaction with the copper substrate will be discussed. Based on this work, we see no limits to the size or number of layers for monocrystalline graphene grown by CVD.

Oral Spin polarization and g-factor enhancement in graphene and graphene nanoribbons in a magnetic field

Igor V. Zozoulenko A. V. Volkov A. A. Shylau and S. Ihnatsenka

Igor.Zozoulenko@liu.se ITN, Linköping University, 60174, Norrköping, Sweden

166

I. Spin splitting in bulk graphene.

We study the effect of electron interaction on the spin splitting and the g factor in graphene in a perpendicular magnetic field using the Hartree and the Hubbard approximations within the ThomasFermi model taking into account the effect of charged impurities in the substrate [1]. We found that the effective g factor is enhanced in comparison to its free-electron value g = 2 and oscillates as a function of the filling factor ν in the range 2 ≤ g* < 4 reaching maxima at ν = 4N = 0, ± 4, ± 8, . . . and minima at ν = 4(N + ½) = ±2, ± 6, ± 10..., with N being the Landau level index, see Fig. 1 We outline the role of charged impurities in the substrate, which are shown to suppress the oscillations of the g factor. This effect becomes especially pronounced with the increase of the impurity concentration, when the effective g factor becomes independent of the filling factor, reaching a value of g* ≈ 2.3. A relation to the recent experiment is discussed.

II. Spin splitting in graphene nanoribbons.

We provide a systematic quantitative description of spin polarization in armchair and zigzag graphene nanoribbons (GNRs) in a perpendicular magnetic field [2]. We first address spinless electrons within the Hartree approximation, studying the evolution of the magnetoband structure and formation of the compressible strips.

We discuss the potential profile and the density distribution near the edges and the difference and similarities between armchair and zigzag edges.

Accounting for the Zeeman interaction and describing the spin effects via the Hubbard term, we study the spin-resolved subband structure and relate the spin polarization of the system at hand to the formation of the compressible strips for the case of spinless electrons. At high magnetic field

the calculated effective g factor varies around a value of g*≈ 2.25 for armchair GNRs and g* ≈ 3 for zigzag GNRs, see Fig. 2. An important finding is that in zigzag GNRs the zero-energy mode remains pinned to the Fermi energy and becomes fully spin polarized for all magnetic fields, which, in turn, leads to a strong spin polarization of the electron density near the zigzag edge. Because of this the effective g factor in zigzag GNRs is strongly enhanced at low fields reaching values up to g* ≈ 30. This is in contrast to armchair GNRs, where the effective g factor at low field is close to its bare value, g = 2.

References [1] A. V. Volkov, A. A. Shylau, and I. V. Zozoulenko, Phys. Rev. B 86, (2012) 155440.

[2] S. Ihnatsenka, I. V. Zozoulenko, Phys. Rev. B 86, (2012) 155407.

Figures

Figure 1: The effective g factor in bulk graphene as a function of the filling factor ν for different concentra-tions of charged impurities, ni = 0%, 0.02%, 0.08%, 0.2%, at the constant magnetic field B = 35T.

ImagineNano2013

ImagineNano2013

167

GRAPHENE 2013

Figure 2: (a), (g) The local spin polarization of the charge density in the sublattice A for the (left) armchair and (right) zigzag ribbons.

The polarization for sublattice B (not shown here) is symmetric with respect to the ribbonâ&#x20AC;&#x2122;s axis. (b), (h) The unit cell occupancy, (c), (i) the spin polarization P, (d), (j) the DOS, (e), (k) the effective g factor, and (f), (l) the conductance as a function of magnetic field calculated in the Hubbard approximation for the (left) armchair and (right) zigzag ribbons. The red lines with solid dots show the spin-up component, and the blue lines with open squares show the spindown component.

Invited Graphene as a potential disruptive material

Amaia Zurutuza

Graphenea, San Sebastian, Spain

Graphene has a variety of intrinsic characteristics that make it an ideal candidate to be applied in many different fields starting from electronics, optoelectronics, energy (solar, batteries, supercapacitors), touch screen and display technology, lighting, sensors, biotechnology, and up to composites. However, to have excellent properties does not ensure a material to have a successful market uptake. There are a series of other requirements that have to be fulfilled in order for a material to become disruptive in industries and markets. A number of potential applications of graphene will be described as examples, such as flexible batteries, [1] solar cells, optical transistors, [2] and light harvesting devices.

[3] In addition, graphene’s prospective to become the next disruptive material will be covered. [4]

excitation Cascade and Multiple Carrier Generation in Graphene,” Nat. Physics, 2013.

[4] Henar Alcalde, Jesus de la Fuente, Bart Kamp, and A. Zurutu a, “Market Uptake Potential of Graphene as a Disruptive Material,” submitted to Proc. IEEE.

References

168

[1] D. Wei, S. Haque, P. Andrew, J. Kivioja, T. Ryhänen, A. Pesquera, A. Centeno, B. Alonso, A. Chuvilin, and A. Zurutu a, “Ultrathin Rechargeable All-Solid-State Batteries Based on Monolayer Graphene,” J. Mater. Chem. A, vol. 1, pp. 3177-3181, 2013.

[2] J. Chen, M. Badioli, P. Alonso-Gon le , S. Thongra anasiri, F. Huth, J. Osmond, M. Spasenovic , A. Centeno, A. Pesquera, P. Godignon, A. Zurutuza Elorza, N. Camara, F.J. García de Abajo, R. Hillenbrand, and F.H.L. Koppens, “Optical Nano-Imaging of GateTunable Graphene Plasmons,” Nature, vol.

487, pp. 77-81, 2012.

[3] T K.J. Tielrooij, J.C.W. Song, S.A. Jensen, A. Centeno, A. Pesquera, A. Zurutuza Elorza, M. Bonn, .S. evitov, and F.H. . Koppens, “Photo-

ImagineNano2013

NanoSpain 2013

Index NanoSpain2013 Contributions Invited

Pag

■ Masakazu Aono (MANA/NIMS, Japan) "Nanoarchitectonics: Basic Concept and Recent Topics"

181

■ Maria Pilar-Bernal (FEMTO-ST-UMR 6174, Besançon, France) "Lithium Niobate Nanophotonics"

184

■ Christian Binek (Univ. of Nebraska, USA) "Isothermal Electric Control of Exchange Bias near Room Temperature"

185

■ Laurent Cognet (LP2N-UMR 5298, Bordeaux, France) "Single Wall Carbon Nanotubes Optical Properties revealed by Single Nanotube Microscopies"

191

■ Etienne Duguet (ICMC8-UPR9048, Bordeaux, France) "Multipod-like Polystyrene/Silica Clusters Designed by Seeded-growth Emulsion Polymerization: Towards Colloidal Molecules and Unconventional Inorganic Nanoparticles"

195

■ Céline Elie-Caille (FEMTO-ST-UMR 6174, Besançon, France) "Combining multiplexed SPRi and AFM approaches for the detection and qualification of circulating blood microparticles sub-populations"

196

■ Andre Gourdon (CEMES-CNRS, France) "Covalent coupling on surfaces in UHV"

207

■ Jim Greer (Tyndall National Institute, Ireland) "Design of Semi-Metal Nanowire Transistor"

208

■ Sébastien Hentz (CEA LETI, Grenoble, France) "Advances in NEMS MASS Spectrometry in the LETI/CALTECH ALLIANCE"

212

■ Xiao Hu (NIMS, Japan) "Electric Field Tuned Topological Insulator"

214

■ Jean-Roch Huntzinger (L2C- UMR 5221, Montpellier, France) "Reversible optical doping of graphene"

216

■ Matthieu Jamet (CEA Grenoble/INAC/LNM, France) "Silicon and Germanium spintronics"

219

■ Haik Jamgotchian (CINaM-CNRS, France) "Synthesis and properties of Silicene layers on metallic substrates"

221

■ Xavier Marie (LPCNO- UMR 5215, Toulouse, France) "Gate Control of the Electron Spin in Semiconductor Quantum Wells"

225

■ Meyya Meyyapan (NASA, USA) "Nanotechnology in Electronic and Sensor Application"

228

■ Gabor Molnár (LCC-UMR 8241, Toulouse, France) "Spin transition at the nanometer scale"

229

■ Alberto Moscatelli (Nature Nanotechnology, UK)

ImagineNano2013

233

171

"The road to publication in Nature Nanotechnology"

Invited

Pag

■ Emiliano Pallecchi (LPN-UPR 20, Marcoussis, France) 247

"Magneto-transport in large area epitaxial graphene grown on SiC:"

■ Fabien Portier (IRAMIS/ SPEC, CEA-Saclay, France) 253

"Coulomb Blockade of shot noise"

■ Bertrand Raquet (LNCMI-UMR 3228, Toulouse, France) 254

"Charge Transport and Magneto-Electric Sub-bands in 1D Nano-Objects"

■ Ralph P. Richter (Univ. J. Fourier (France), Univ. San Sebastian & CIC biomaGUNE (Spain)) "Biomolecular hydrogels - from supramolecular structure and dynamics to biological function"

259

■ José Rivas (INL, Portugal) 261

"Magnetic particles and clusters through a cross-disciplinary approach"

■ Didier Tonneau (Aix-Marseille University, France) 272

"High resolution XRF using capillary optics"

■ Javier Villegas (UMPhy-UMR 132 CNRS/THALES, Palaiseau, France) 273

"Nanoscale effects at complex-oxide superconducting/ferroic hybrids"

■ Ronald Wiesendanger (Univ. of Hamburg, Germany) 275

"Exploring Magnetism in the Nanoworld"

Oral

Pag

■ Elena Bailo (WITec GmbH, Germany) 182

"Characterization of Carbon Nanomaterials with a Confocal Raman AFM"

■ Ross Brown (IPREM, France) "Maya Blue: archaeological puzzle and source of inspiration for nano-structured pigments"

187

■ Mary Cano (Instituto Catalán de Nanotecnlogía ICN, Spain) 189

"Liposomes as novel immunostimulant delivery systems in aquaculture"

■ Yolanda De Miguel (Tecnalia, Spain) "Design and development of novel nanoparticles and nanostructured coatings for a wide range of industrial applications"

192

■ Jose Maria De Teresa (CSIC-Universidad de Zaragoza, Spain) "Effects of Ga irradiation on the nucleation and propagation of magnetic domain walls in cobalt nanostructures grown by focused-electron-beam-induced deposition"

193

■ José Miguel García-Martín (IMM-CSIC , Spain) "Nanoporous gold thin films deposited by magnetron sputtering: tayloring the porosity"

197

■ Roberto Ghiandoni (NanoSight Limited, United Kingdom) "Nanosuspension characterization: Application of NTA to research from drug delivery to exosomes research"

199

■ Peter Gnauck (Carl Zeiss Microscopy, Germany) "Helium Ion Microscopy. Extending the frontiers of nanotechnology"

201

■ Raquel Gómez-Medina (Universidad Autónoma de Madrid, Spain)

172

"Tractor beams for semiconductor spheres"

203

ImagineNano2013

Oral

Pag

■ Jesús Antonio Gonzalez Gomez (Universidad de Cantabria, Spain) "Pressure dependence of Raman modes in Graphene Oxide (GO)"

205

■ Jon Gutierrez (Universidad del País Vasco, Spain) "Nucleation of the electroactive ß-phase, dielectric and magnetic response of poly (vinylidene fluoride) composites with Fe2O3 nanoparticles"

210

■ Ali Hilal-Alnaqbi (UAEU, United Arab Emirates) "Development of a novel method for the identification of mouse gastric stem cells Using Raman Spectroscopy"

213

■ Inhar Imaz (Institu Catala de Nanotecnologia, Spain) "A spray-drying strategy for synthesis of nanoscale metal–organic frameworks and their assembly into hollow superstructures"

217

■ Gerald Kada (Agilent Technologies, United States) "Advances in Quantitative Impedance Measurement and Dopant Level Profiling Using Scanning Microwave Microscopy"

223

■ Hong Seok Kang (Jeonju University, South Korea) "DFT Studies of One-Dimensional Systems of Metal-porphyrin Tapes and CuCN Nanowires"

224

■ Virginia Martinez-Martinez (Universidad del País Vasco, Spain) "One dimensional Ordered Materials for Optical Applications: Pyronine Y dye into Aluminophosphates with different nanopore size"

226

■ Hipolito Montejano Lozoya (BIOINICIA, S.L., Spain) "High Throughput Electrospinning"

231

■ Rafael Morales (University of the Basque Country, Spain) "Exchange bias dependence in gradually patterned antiferromagnet"

232

■ Sohel Murshed (University of Lisbon, Portugal) "Morphological and Structural Characterization of ZnO and TiO 2 Nanoparticles"

234

■ Takashi Nakamura (National Institute of Advanced Industrial Science and Technology, Japan) "Preparation of Copper Nitride Nanoparticles in Long-chain Alcohol and Its Thermal Decomposition Property"

236

■ Enrique Navarro (Pyrenean Institute of Ecology (CSIC), Spain) "The ratio protein-silver modulates the availability of ionic silver and the potential toxicity of silver nanoparticles: applications for cheaper and more effective consumer products"

238

■ Frank Nouvertne (RAITH GmbH, Germany) "Innovative Patterning Strategies and Process Control using Multi-Application Nanolithography Tools for Microfiltration, Solar Cells and Bragg Gratings"

240

■ Xavier Obradors (ICMAB - CSIC, Spain) "Bottom-up approach to epitaxial complex oxide nanostructures and nanocomposite thin films with outstanding magnetic, superconducting and electronic properties"

242

■ Anna Orlova (S.Petersburg NRU ITMO, Russia) "Interaction of ammonia vapors with CdSe/ZnS quantum dots in porous matrices"

244

■ Maria C. Paiva (PIEP - Pole for Innovation in Polymer Engineering - Universidade do Minho, Portugal) "Poly(lactic acid)-modified carbon nanotubes for poly(lactic acid) composites"

246

■ Joaquín Penide (Universidad de Vigo, Spain)

ImagineNano2013

248

173

"Optimization of glass nanofibers productivity in Laser Spinning process"

Oral

Pag

■ Mick Phillips (Asylum Research, an Oxford Instruments company, United Kingdom) 250

"Novel mechanical properties of graphene using atomic force microscopy"

■ Joerg Polte (Humboldt University to Berlin, Germany) 252

"Understanding Colloidal Nanoparticle Growth"

■ Aritz Retolaza (CIC MICROGUNE, Spain) 255

"Pump size dependence of organic second-order distributed feedback lasers"

■ Alan Reynolds (Brunel University, United Kingdom) "Synthesis of silver nanoparticles from seed washings and their antibacterial activity"

257

■ Ainara Rodriguez (CIC microGUNE, Spain) "Femtosecond Laser Induced Periodic Surface Nanostructuring of Platinum Thin Films"

263

■ Jose San Juan (Universidad del Pais Vasco, Spain) "Nano-scale Superelastic behavior of Shape Memory Alloys for potential MEMS applications"

265

■ Violeta Simic-Milosevic (SPECS Surface Nano Analysis GmbH, Germany) 267

"Joule-Thomson SPM for in situ sample analysis in extreme environments"

■ Fabienne Testard (CEA, France) "Understanding of the Size Control of Biocompatible Gold Nanoparticles in Millifluidic Channels: in situ SAXS/XANES/UV"

268

■ Grigory Tkachov (Wuerzburg University, Germany) "Spin-helical transport in normal and superconducting topological insulator materials"

270

■ Ivar Zapata (Universidad Autónoma de Madrid, Spain) "Ratchets: from driven and noisy to stationary and deterministic optical ratchets"

276

■ Araceli Zavaleta (Colegio de Postgraduados, Mexico)

174

"A Culinary Herb Extract to Synthesize Silver Nanoparticles"

277

ImagineNano2013

Index NanoSpain2013 Contributions Alphabetical Order I:Invited / O: Oral

Pag

■ Masakazu Aono (MANA/NIMS, Japan) "Nanoarchitectonics: Basic Concept and Recent Topics"

I

181

O

182

I

184

I

185

O

187

O

189

I

191

O

192

O

193

I

195

I

196

O

197

O

199

O

201

O

203

O

205

■ Elena Bailo (WITec GmbH, Germany) "Characterization of Carbon Nanomaterials with a Confocal Raman AFM"

■ Maria Pilar-Bernal (FEMTO-ST-UMR 6174, Besançon, France) "Lithium Niobate Nanophotonics"

■ Christian Binek (Univ. of Nebraska, USA) "Isothermal Electric Control of Exchange Bias near Room Temperature"

■ Ross Brown (IPREM, France) "Maya Blue: archaeological puzzle and source of inspiration for nano-structured pigments"

■ Mary Cano (Instituto Catalán de Nanotecnlogía ICN, Spain) "Liposomes as novel immunostimulant delivery systems in aquaculture"

■ Laurent Cognet (LP2N-UMR 5298, Bordeaux, France) "Single Wall Carbon Nanotubes Optical Properties revealed by Single Nanotube Microscopies"

■ Yolanda De Miguel (Tecnalia, Spain) "Design and development of novel nanoparticles and nanostructured coatings for a wide range of industrial applications"

■ Jose Maria De Teresa (CSIC-Universidad de Zaragoza, Spain) "Effects of Ga irradiation on the nucleation and propagation of magnetic domain walls in cobalt nanostructures grown by focused-electron-beam-induced deposition"

■ Etienne Duguet (ICMC8-UPR9048, Bordeaux, France) "Multipod-like Polystyrene/Silica Clusters Designed by Seeded-growth Emulsion Polymerization: Towards Colloidal Molecules and Unconventional Inorganic Nanoparticles"

■ Céline Elie-Caille (FEMTO-ST-UMR 6174, Besançon, France) "Combining multiplexed SPRi and AFM approaches for the detection and qualification of circulating blood microparticles sub-populations"

■ José Miguel García-Martín (IMM-CSIC , Spain) "Nanoporous gold thin films deposited by magnetron sputtering: tayloring the porosity"

■ Roberto Ghiandoni (NanoSight Limited, United Kingdom) "Nanosuspension characterization: Application of NTA to research from drug delivery to exosomes research"

■ Peter Gnauck (Carl Zeiss Microscopy, Germany) "Helium Ion Microscopy. Extending the frontiers of nanotechnology"

■ Raquel Gómez-Medina (Universidad Autónoma de Madrid, Spain) "Tractor beams for semiconductor spheres" "Pressure dependence of Raman modes in Graphene Oxide (GO)"

ImagineNano2013

175

■ Jesús Antonio Gonzalez Gomez (Universidad de Cantabria, Spain)

I:Invited / O: Oral

Pag

■ Andre Gourdon (CEMES-CNRS, France) "Covalent coupling on surfaces in UHV"

I

207

I

208

O

210

I

212

O

213

I

214

I

216

O

217

I

219

I

221

O

223

O

224

I

225

O

226

I

228

I

229

O

231

O

232

I

233

O

234

■ Jim Greer (Tyndall National Institute, Ireland) "Design of Semi-Metal Nanowire Transistor"

■ Jon Gutierrez (Universidad del País Vasco, Spain) "Nucleation of the electroactive ß-phase, dielectric and magnetic response of poly (vinylidene fluoride) composites with Fe2O3 nanoparticles"

■ Sébastien Hentz (CEA LETI, Grenoble, France) "Advances in NEMS MASS Spectrometry in the LETI/CALTECH ALLIANCE"

■ Ali Hilal-Alnaqbi (UAEU, United Arab Emirates) "Development of a novel method for the identification of mouse gastric stem cells Using Raman Spectroscopy"

■ Xiao Hu (NIMS, Japan) "Electric Field Tuned Topological Insulator"

■ Jean-Roch Huntzinger (L2C- UMR 5221, Montpellier, France) "Reversible optical doping of graphene"

■ Inhar Imaz (Institu Catala de Nanotecnologia, Spain) "A spray-drying strategy for synthesis of nanoscale metal–organic frameworks and their assembly into hollow superstructures"

■ Matthieu Jamet (CEA Grenoble/INAC/LNM, France) "Silicon and Germanium spintronics"

■ Haik Jamgotchian (CINaM-CNRS, France) "Synthesis and properties of Silicene layers on metallic substrates"

■ Gerald Kada (Agilent Technologies, United States) "Advances in Quantitative Impedance Measurement and Dopant Level Profiling Using Scanning Microwave Microscopy"

■ Hong Seok Kang (Jeonju University, South Korea) "DFT Studies of One-Dimensional Systems of Metal-porphyrin Tapes and CuCN Nanowires"

■ Xavier Marie (LPCNO- UMR 5215, Toulouse, France) "Gate Control of the Electron Spin in Semiconductor Quantum Wells"

■ Virginia Martinez-Martinez (Universidad del País Vasco, Spain) "One dimensional Ordered Materials for Optical Applications: Pyronine Y dye into Aluminophosphates with different nanopore size"

■ Meyya Meyyapan (NASA, USA) "Nanotechnology in Electronic and Sensor Application"

■ Gabor Molnár (LCC-UMR 8241, Toulouse, France) "Spin transition at the nanometer scale"

■ Hipolito Montejano Lozoya (BIOINICIA, S.L., Spain) "High Throughput Electrospinning"

■ Rafael Morales (University of the Basque Country, Spain) "Exchange bias dependence in gradually patterned antiferromagnet"

■ Alberto Moscatelli (Nature Nanotechnology, UK) "The road to publication in Nature Nanotechnology"

■ Sohel Murshed (University of Lisbon, Portugal)

176

"Morphological and Structural Characterization of ZnO and TiO 2 Nanoparticles"

ImagineNano2013

I:Invited / O: Oral

Pag

■ Takashi Nakamura (National Institute of Advanced Industrial Science and Technology, Japan) "Preparation of Copper Nitride Nanoparticles in Long-chain Alcohol and Its Thermal Decomposition Property"

O

236

O

238

O

240

O

242

O

244

O

246

I

247

O

248

O

250

O

252

I

253

I

254

O

255

O

257

I

259

I

261

O

263

O

265

O

267

O

268

■ Enrique Navarro (Pyrenean Institute of Ecology (CSIC), Spain) "The ratio protein-silver modulates the availability of ionic silver and the potential toxicity of silver nanoparticles: applications for cheaper and more effective consumer products"

■ Frank Nouvertne (RAITH GmbH, Germany) "Innovative Patterning Strategies and Process Control using Multi-Application Nanolithography Tools for Microfiltration, Solar Cells and Bragg Gratings"

■ Xavier Obradors (ICMAB - CSIC, Spain) "Bottom-up approach to epitaxial complex oxide nanostructures and nanocomposite thin films with outstanding magnetic, superconducting and electronic properties"

■ Anna Orlova (S.Petersburg NRU ITMO, Russia) "Interaction of ammonia vapors with CdSe/ZnS quantum dots in porous matrices"

■ Maria C. Paiva (PIEP - Pole for Innovation in Polymer Engineering - Universidade do Minho, Portugal) "Poly(lactic acid)-modified carbon nanotubes for poly(lactic acid) composites"

■ Emiliano Pallecchi (LPN-UPR 20, Marcoussis, France) "Magneto-transport in large area epitaxial graphene grown on SiC:"

■ Joaquín Penide (Universidad de Vigo, Spain) "Optimization of glass nanofibers productivity in Laser Spinning process"

■ Mick Phillips (Asylum Research, an Oxford Instruments company, United Kingdom) "Novel mechanical properties of graphene using atomic force microscopy"

■ Joerg Polte (Humboldt University to Berlin, Germany) "Understanding Colloidal Nanoparticle Growth"

■ Fabien Portier (IRAMIS/ SPEC, CEA-Saclay, France) "Coulomb Blockade of shot noise"

■ Bertrand Raquet (LNCMI-UMR 3228, Toulouse, France) "Charge Transport and Magneto-Electric Sub-bands in 1D Nano-Objects"

■ Aritz Retolaza (CIC MICROGUNE, Spain) "Pump size dependence of organic second-order distributed feedback lasers"

■ Alan Reynolds (Brunel University, United Kingdom) "Synthesis of silver nanoparticles from seed washings and their antibacterial activity"

■ Ralph P. Richter (Univ. J. Fourier (France), Univ. San Sebastian & CIC biomaGUNE (Spain)) "Biomolecular hydrogels - from supramolecular structure and dynamics to biological function"

■ José Rivas (INL, Portugal) "Magnetic particles and clusters through a cross-disciplinary approach"

■ Ainara Rodriguez (CIC microGUNE, Spain) "Femtosecond Laser Induced Periodic Surface Nanostructuring of Platinum Thin Films"

■ Jose San Juan (Universidad del Pais Vasco, Spain) "Nano-scale Superelastic behavior of Shape Memory Alloys for potential MEMS applications"

■ Violeta Simic-Milosevic (SPECS Surface Nano Analysis GmbH, Germany) "Joule-Thomson SPM for in situ sample analysis in extreme environments"

■ Fabienne Testard (CEA, France)

ImagineNano2013

177

"Understanding of the Size Control of Biocompatible Gold Nanoparticles in Millifluidic Channels: in situ SAXS/XANES/UV"

I:Invited / O: Oral

Pag

■ Grigory Tkachov (Wuerzburg University, Germany) "Spin-helical transport in normal and superconducting topological insulator materials"

O

270

I

272

I

273

I

275

O

276

O

277

■ Didier Tonneau (Aix-Marseille University, France) "High resolution XRF using capillary optics"

■ Javier Villegas (UMPhy-UMR 132 CNRS/THALES, Palaiseau, France) "Nanoscale effects at complex-oxide superconducting/ferroic hybrids"

■ Ronald Wiesendanger (Univ. of Hamburg, Germany) "Exploring Magnetism in the Nanoworld"

■ Ivar Zapata (Universidad Autónoma de Madrid, Spain) "Ratchets: from driven and noisy to stationary and deterministic optical ratchets"

■ Araceli Zavaleta (Colegio de Postgraduados, Mexico)

178

"A Culinary Herb Extract to Synthesize Silver Nanoparticles"

ImagineNano2013

A b s t r act s Alphabetical order

NanoSpain 2013

Invited Nanoarchitectonics: Basic Concept and Recent Topics

Masakazu Aono

AONO.Masakazu@nims.go.jp International Center for Materials Nanoarchitectonics (MANA) National Institute for Materials Science (NIMS) Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan

3)

4)

References [1] MANA Special Issue on “Advances in Nanomaterials Research and Nanoarchitectonics“: Science and Technology of Advanced Materials Vol. 11 (2010) No. 5 and Vol. 12 (2011) No. 4.

[2] MANA Special Issue on “Materials Nanoarchitectonics at NIMS“: Advanced Materials Vol. 24 (2012) No.2.

Nanosheet technology (one of the most important new materials creation methods based on nanoarchitectonics): This is a unique technology but versatile enough to be

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1)

2)

applied to create various new materials such as novel dielectric, magnetic, photolectric and superconducting materials.

Atomic switch and its derivatives: They are not only useful as beyond-CMOS memory and logic devices but also promising in the realization of material-based neuromorphic computational circuits (artificial brain).

Artificial Photosynthesis: We have already succeeded in the photosynthesis of methane (CH4) for example by the use of tungsten suboxide (W18O49). As the next step, we are making a series of studies to increase the efficiency of photosynthesis.

Decoherence-free novel quantum bit: Recent remarkable theoretical and experimental researches in MANA are being combined for this purpose.

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In 2007, Japan’s Government launched the World Premier International Research Center Initiative, i.e. WPI Program. Our International Center for Materials Nanoarchitectonics (MANA) was organized as one of the first five WPI centers.

The reason why we use the new word nanoarchitectonics in the name of MANA is that we believe conventional nanotechnology has to be revolutionized by the concept expressed by the new word nano-architectonics in order to draw the full ability of nanotechnology. Nanoarchitectonics can be regarded as a novel technology system allowing to arrange nanoscale structural units, which are typically a group of atoms or molecules or a complex of them, in an intended configuration. However, nanoarchitectonics is not a simple extension of conventional nanotechnology but aims to move to a new paradigm for nano-technology in materials development, where novel materials with an emergent property are created by designing and controlling mutual interactions between nanoscale structural units. Nanoarchitectonics therefore claims that the conventional analytic view of nanotechnology must yield to a certain synthetic view and also that it must be looked squarely that the conventional concept of precise structural control, which has been widely accepted in microtechnology, does not necessarily hold at the nanoscale.

In this paper, the following four topics are discussed as typical examples of recent researches based on nanoarchitectonics done in MANA.

Oral Characterization of Carbon Nanomaterials with a Confocal Raman AFM

Elena Bailo F. Vargas T. Dieing and U. Schmidt

ute.schmidt@witec.de WITec GmbH Lise-Meitner Str. 6, 89081 Ulm, Germany

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Carbon is known to exist in a number of allotropes which range from single crystalline diamond - the hardest of all known materials, to the soft, layer based graphite. The discovery by Novoselov and Geim [1] of a simple method to transfer a single atomic layer of carbon from the c-face of graphite to a substrate suitable for measurements of its electrical and optical properties has led to an increased interest in studying and employing twodimensional model systems. An overview of electron and phonon properties of graphene and their relationship to the one-dimensional form of carbon known as nanotubes can be found in [2].

The unique chemical, mechanical, electrical, and optical properties of graphene lead to its many application possibilities such as: single molecule detectors, high-strength lowweight new materials, design of new semiconductor devices, etc.

An important goal however, is the detection of such angstrom-thick two dimensional sheets and precisely determine the number of layers forming the graphene flake. The aim of this contribution is to show how a confocal Raman AFM can contribute to the characterization of such small materials and devices. In the past two decades, AFM (atomic force microscopy) was one of the main techniques used to characterize the morphology of nano-materials spread on nanometer-flat substrates. From such images it is possible to gain information about the physical dimensions of the material on the nanometer scale, without additional information about their chemical composition, crystallinity or stress state.

On the other hand, Raman spectroscopy is known to be used to unequivocally determine the chemical composition of a material. By combining the chemical sensitive Raman spectroscopy with high resolution confocal optical microscopy, the

analyzed material volume can be reduced below 0.02 Âľm, thus leading to the ability to acquire Raman images with diffraction limited resolution from very flat surfaces [3, 4]. The combination of confocal Raman microscopy with Atomic Force Microscopy (AFM) is a breakthrough in microscopy. Using such a combination, the high spatial and topographical resolution obtained with an AFM can be directly linked to the chemical information provided by confocal Raman spectroscopy [5].

An example of a confocal Raman-AFM measurement is illustrated in the figures of this abstract. Fig. 1 shows the AFM topography image of a graphene flake deposited on a Si substrate.

This image was recorded in AFM AC mode and it reveals the presence of mono-, bi- and multi-layers of carbon, as highlighted in the two cross sections.

A Raman image was recorded from the same sample area by acquiring a spectral array of 85x50 complete Raman spectra. A typical Raman spectrum of graphene deposited on a Si-substrate is shown in Fig. 2. The thousands of Raman spectra were evaluated using peak fitting algorithms, which are very sensitive to small variations of Raman band position and width. The Raman image presented in Fig. 2 highlights the variations of the G-band within the analyzed graphene. The monolayer of graphene (brown color) can be clearly discriminated from a graphene bilayer (pink color).

In yellow color a flipped over graphene sheet is presented.

The various data acquisition and evaluation methods will be discussed in this contribution.

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References [1] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos,I. V. Grigorieva, A. A. Firsov, Science. 306, Nr. 5696 (2004) 666.

[2] C. Charlier, P. C. Eklund, J. Zhu, and A. C. Ferrari, Electron and phonon properties of graphene: their relationship with carbon nanotubes In: A. Jorio, G. Dresselhaus, and M. S. Dresselhaus, M.S., (eds.) Carbon Nanotubes: Advanced Topics in the Synthesis, Structure, Properties and Applications. Topics in Applied Physics 111. Springer-Verlag, New York, USA, pp. 673 (2008).

[3] P. Lasch, A. Hermelink and D. Naumann, The Analyst, (2009) 1.

[4] A. Jungen, V. N. Popov, C. Stampfer, C. Durrer, S. Stoll, and C. Hierold Physical Review, 75, (2007) 405.

[5] U. Schmidt, S. Hild, W. Ibach and O. Hollricher, Macromol. Symp. 230 (2005) 133.

Figure 1: AFM topography image of a graphene flake deposited on a Si substrate (left) and cross sections along the two directions marked in the topography image (right).

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Figures

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Figure 2: Confocal Raman image of the same graphene flake as in Fig. 1, revealing the optical properties of the various graphene layers (left) and averaged Raman spectrum of the graphene flake.

Invited

Lithium Niobate Nanophotonics

Optics Departement, FEMTO-ST, UMR 6174, CNRS, 16 Route de Gray, 25030 Besancon (France)

Maria-Pilar Bernal

maria-pilar.bernal@univ-fcomte.fr

184

The recent development of integrated photonic crystals within planar waveguides can help implementing compact devices with fully integrable functions. In these devices, light is confined into the crystal by a classical waveguide construction.

Lithium niobate (LN) is a suitable material for 2D photonic crystals because of its high refractive index. Moreover, it is a ferroelectric crystal of great interest to the optics, telecommunications and laser community due to its large electro-optic and non-linear coefficients and extensive applications in piezoelectric, acousto-optic, pyroelectric and photorefractive devices.

However, the realisation of high aspect ratio submicron structure in LN is up to date a challenging problem due to its well known resistivity towards standard machining techniques like wet etching.

In this seminar, I will present the design, fabrication, and optical characterisation of novel infra-red tunable lithium niobate photonic crystal devices.

Slow light propagation allows enhancement of the tunability, thus, we have experimentally observed a spectacular increase on the acoustic, elecro-optic and pyroelectric properties of the nanodevices.

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Invited Isothermal Electric Control of Exchange Bias near Room Temperature 1

Department of Physics & Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0111, USA Canadian Light Source Inc., University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 0X4 3 Department of Physics, 257 Flarsheim Hall, University of Missouri, Kansas City KS 64110, USA 4 Brookhaven National Laboratory, National Synchrotron Light Source, Upton, NY, 11973, USA

1

Christian Binek 1 1 1 He Xi , Wang Yi , Wu N. , 1 1 Wysocki A. , Komesu T. , Lanke U.2, Caruso A.N.3, 4 Vescovo E. , 1 Belashchenko K.D. and 1 Dowben P.A.

2

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controlled EB and promise a new route towards voltage-controlled spintronics.

Acknowledgements: Financial support from NSFC, MOST and CAS is acknoledged.

References [3] Xi He, Yi Wang, Ning Wu, A. N. Caruso, E. Vescovo., K. D. Belashchenko, P. A. Dowben & Ch. Binek, Nature Mater.9, 579â&#x20AC;&#x201C;585 (2010).

[4] N. Wu, Xi He, A. L. Wysocki, U. Lanke, T. Komesu, K. D. Belashchenko, Ch. Binek, and P. A. Dowben, Phys. Rev. Lett. 106, 087202 (2011).

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Figures

Figure 1: Cartoon of chromia in single domain states. Arrows depict spins of Cr3+-ions. Circles show O2--ions. Rough (0001) surface of AF single domain shows sizable spin polarization.

185

Voltage-controlled spintronics is of particular importance to continue progress in information technology through reduced power consumption, enhanced processing speed, integration density, and functionality in comparison with present day CMOS electronics. Almost all existing and prototypical solid-state spintronic devices rely on tailored interface magnetism, enabling spinselective transmission or scattering of electrons.

Controlling interface magnetism by purely electrical means is a key challenge to better spintronics. I report on the antiferromagnetic (AF) magnetoelectric (ME) Cr2O3 (chromia) for voltagecontrolled magnetism. Robust isothermal electric control of exchange bias (EB) is achieved near room temperature in the EB heterostructure Cr2O3(0001)/CoPd [1]. Magnetometry and investigations of voltage-controlled EB provide macroscopic evidence for electrically switchable equilibrium boundary magnetization (BM). Firstprinciples calculations and symmetry considerations show that BM is a generic property at interfaces of ME antiferromagnets (Fig. 1).

Isothermal switching between two degenerate AF single domain states is achieved when an electric field, E, and magnetic field, H, are simultaneously applied and their product overcomes a critical threshold. The sign of E H selects the AF registration. The BM is strongly coupled to the bulk AF order parameter and follows the latter during switching. Exchange between the BM and the adjacent ferromagnet gives rise to switching of the EB-field. Spin-resolved UPS of a chromia (0001) surface provides averaged information of the BM. Laterally resolved X-ray PEEM (Fig.2) and Tdependent MFM reveal microscopic details [2].

Our data provide an understanding of electrically

cbinek@unl.edu

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186

Figure 2: (a-c) Cr2O3 (0001) film imaged by XMCD-PEEM at the Cr Ledge. (a) No contrast at 584 K. (b) Multi-domain state after zerofield cooling. Inset shows spin polarization with respect to positively circularly polarized incident light. (c) Nearly single-domain state at 223 K after ME field-cooling. (d) XMCD spectrum recorded from within one domain.

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Oral Maya Blue: archaeological puzzle and source of inspiration for nano structured pigments

Ross Brown

1

C. Dejoie2,3, P. Martinetto2 E. Dooryhée2,4, A. Marbeuf5, S. Blanc1, P. Bordat1 I. Baraille1, E. Van Eslande6 P. Walter6.and M. Anne2

1

IPREM-ECP, CNRS and Université de Pau et des Pays de l'Adour, Hélioparc, 2 avenue Pierre Angot, F-64053 Pau Cedex 9, France 2 Institut Néel, (UPR 2940 CNRS), 25 avenue des Martyrs, BP 166, F-38042 Grenoble Cedex 9, France 3 Lab. Crystallography, ETH-Zürich, Wolfgang Pauli-Str. 10, 9093 Zürich, Switzerland 4 National Synchrotron Light Source-II, Brookhaven, Upton, NY 11973, USA 5 Laboratoire Ondes et Matière en Aquitaine , CNRS & Université Bordeaux 1, 351 crs de la Libération, 33405 Talence Cedex, France 6 LAMS, CNRS & Université Pierre et Marie Curie, Site Le Raphael, 3, rue Galilée, 94200 Ivry, France

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the material. Our experimental conclusion, that stability derives more from steric screening of the dye in the channels than from chemical complexation, is supported by the molecular simulations. This screening is exhibited in the association of indigo with silicalite, forming a pigment analogous to MB, figure 2, resistant to photodegradation and oxidation by nitric acid.

[1] H. Van Olphen, Science, 154 (1966) 645-6.

[2] G. Chiari, R. Giustetto, J. Druzik, E. Doehne, G. Ricchiardi, Appl. Phys. A, 90 (2008) 3-7.

[3] B. Hubbard, W. Kuang, A. Moser, G. A. Facey, C. Detellier, Clays and Clay Minerals, 51 (2003) 318 26.

[4] E. Fois, E. Gamba, A. Tilocca, Microporous Mesoporous Mater. 57 (2003) 263-72.

[5] A. Tilocca, E. Fois, J. Phys. Chem C, 113 (2009) 8683-87.

[6] C. Dejoie, PhD Thesis, Université J. Fourier de Grenoble, 2009.

[7] C. Dejoie, P. Martinetto, E. Dooryhée, P. Strobel, S. Blanc, P. Bordat, R. Brown, F. Porcher, M. Sanchez del Rio, and M. Anne, ACS Applied Materials & Interfaces, 2 (2010) 2308– 16.

[8] C. Dejoie, P. Martinetto, E. Dooryhée, E. van Elselande, S. Blanc, P. Bordat, R. Brown, F. Porcher, M. Anne, Applied Spectroscopy, 64 (2010) 1131–38.

[9] P. Bordat et al., in preparation for J. Phys Chem C (2013).

[10] R. J. Gettens, Am. Antiquity 7 (1926) 557-64.

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References

187

The turquoise blue pigment Maya Blue (MB) was widely used in Mesoamerica up to ca. 1500, on pottery, textiles and frescos (figure 1). Its brightness and durability are remarkable, specially considered in the light of its deceptively simple present day synthesis, by heating together powdered indigo and palygorskite clay [1].

Palygorskite occurs as nano-fibres, typically some tens of nm in width and up to a few µm long. The crystal structure defines rectangular ca. 0.7x1.2 nm interior channels and surface grooves. It is generally agreed that indigo acquires chemical and physical stability by entering these channels and grooves.

Yet despite some years of study with the experimental and theoretical tools of modern analytical materials science [2-5], the detailed structure of MB, and its relation to its astounding chemical and physical stability, remain subjects of debate. While study of archaeological samples and laboratory synthesized MB have shed much light on the problem, better understanding can come from contrasting and comparing MB with analogous, archaeo-inspired materials, both successful and unsuccessful, based on the same principles of fitting an organic dye into an inorganic host matrix with well defined nanocavities.

Here, we apply this novel approach to MB[6] and zeolite-based analogues [7-9], employing a variety of techniques, including in situ XRD, thermogravimetric analysis, optical spectroscopy, confocal microscopy and molecular modelling, to propose an updated view of the structure and dynamics of this fascinating material. The results indeed point to indigo being sequestered in the channels of palygorskite, but call into question current understanding of the reasons for the stability of

ross.brown@univ-pau.fr

Figures

Figure 1: a) Fresco fragment from Cacaxtla, coloured with Maya Blue; (b): molecular dynamics simulation of indigo in a palygorskite channel (inset), host cut away except Mg (pink) to show water and indigo.

188

Figure 2: Normalised Kubelka-Munk transforms, F(R), of the UVvisible diffuse reflectance of indigonano-porous guest-host systems (2%wt. Indigo): (a) reconstituted MB; (b) indigo-silicalite. Symbols: □ unheated mixtures; ○ heated hybrids; ∆ heated hybrids after the nitric acid test. Persistence of the blue colour in presence of nitric acid (the Gettens test [10]) is a hallmark of Maya Blue.

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Oral Liposomes as novel immunostimulant delivery systems in aquaculture

2

Mary Cano 1,2 A. Ruyra 1 S. MacKenzie N. Roher1 and 1,3 D. Maspoch

1

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lipopolysaccharide (LPS) and the synthetic analogue of dsRNA virus, poly(I:C), both virtually present in all fish species.

Liposomes encapsulating both immunostimulants are prepared by thin film hydratation method using the DLPC: Cholesterol:Cholesteryl:PEG lipid mixture [3]. Through this methodology, highly homogeneous small unilamellar vesicles with a mean particle size of 125.8 nm can be prepared (see Figure 1). Liposomes that show a positive surface charge (+1.37 mV) seems to be ideal for encapsulating both LPS and poly (I:C). Indeed, the attractive interaction between the negative charge of both immunostimulants and the positive surface charge of liposomes results in the near-perfect conditions to achieve the highest encapsulation efficiencies of 22.3 % for LPS and 99.6% for poly (I:C). Confocal microscope images of fluorescentlabeled liposomes demonstrate that both LPS and poly (I:C) are incorporated into their cationic lipid bilayer.

We show that this liposomal carrier presents a low toxicity in vitro using three different cellular models and in vivo using zebrafish embryos and larvae at the therapeutic and immunomodulatory doses. In addition, liposomal uptake is confirmed by incubating fluorescent-labelled liposomes with zebrafish hepatocytes and trout macrophage plasma membrane, observing high liposome internalization mainly through caveolae-mediated endocytosis. Importantly, we anticipate that this liposomal cocktail elicits a specific proinflammatory and anti-viral response in both zebrafish hepatocyte cells and trout macrophages, after studying the changes in the expression of different immune related genes, which represents a completely new approach in fish health [4].

In conclusion, the induction of specific immune responses with liposomal immunostimulant

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In the last three decades, world food fish production from aquaculture has expanded by almost 12 times. Nowadays, aquaculture contributes nearly half (47.3%) of the world’s food fish consumption. In this sector, most economic losses related to fish diseases are mainly caused by mortality and reduce growth. It is estimated that approximately 50% of all fish are lost due to disease before they reach the market [1].

Therefore, the development of sustainable aquaculture, a strategic sector to feed the everincreasing human population, relies on disease prevention through implementation of preventive immunostimulation and effective vaccination strategies. With the advent of liposomal vaccines, one can begin to conceive new non-invasive, nonstressful and easy-to-manage methods for administering immunostimulants and vaccines to a large number of cultured fish at any time of its life cycle [2]. Liposomes are hollow spherical, safe and well-tolerated assemblies formed by lipid bilayers that can be tailored (via composition, size and charge) to efficiently entrap a wide variety of immunostimulants and vaccines.

This encapsulation provides the obvious potential advantages of increasing their stability and protection, thus enhancing their immune response and disease protection, and opening up the possibility to design more efficient immunostimulant-vaccine cocktails.

Herein we present a unique delivery system based on the encapsulation of a cocktail of immunostimulants in nanoliposomes with the ability to protect them against a pathogenic challenge and to stimulate, for the first time, two potent innate immunity pathways virtually present in all fish species, which represents a breakthrough in fish health. The immunostimulant cocktail selected for this study are the bacterial

mary.cano@icn.cat daniel.maspoch@icn.cat

189

Institut de Biotecnologia i Biomedicina (IBB), Esfera UAB, 08193 Bellaterra, Spain.

CIN2 (ICN-CSIC), Catalan Institute of Nanotechnology, Esfera UAB, 08193 Bellaterra, Spain. ³Institució Catalana de Recerca i Estudis Avançats (ICREA), 08100 Barcelona, Spain 2

formulations is found to be a very promising strategy to improve disease control in fish farms.

Further work is ongoing to evaluate the in vivo biodistribution of this liposomal cocktail in aquacultured fishes and their affinity to specific fish organs. Different administration routes will be evaluated - injection, oral and immersion- to finally establish a rational immunisation protocols.

Liposome stability and therapeutic efficacy studies with bacterial and viral challenge are also in progress.

References [1] O. Evensen, Options Mediterraneennes (2009) 1.

[2] P. Nordly, H.B. Madsen, H.M. Nielsen, C. Foged, Expert Opin. Drug Deliv. 6 (2009) 657.

[3] A.D. Bangham, M.M. Standish, J.C. Watkins, J. Mol. Biol. 13 (1965) 238.

[4] L.-Y. Zhu, L. Nie, G. Zhu, L.-X. Xiang, J.-Z. Shao, Dev Comp Immunol. (2012) 1.

Figures

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Figure 1: a) Fluorescent microscopy image of IS liposomes biodistributed in zebrafish. b) Cryo-TEM image of DLPC:Cholesterol: Cholesteryl:PEG liposomes containing immunostimulants. C) Model of liposomes encapsulating LPS (red) and poly (I:C) (green).

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Invited Single Wall Carbon Nanotubes Optical Properties revealed by Single Nanotube Microscopies

Laurent Cognet

lcognet@u-bordeaux1.fr Institut d'Optique â&#x20AC;&#x201C; CNRS (LP2N) University of Bordeaux 351, cours de la liberation 33405 Talence France

Current methods for producing single-walled carbon nanotubes (SWNTs) lead to heterogeneous samples containing mixtures of metallic and semiconducting species with a variety of lengths and defects. Optical detection at the single nanotube level offers the possibility to examine these heterogeneities, which is fundamental for accessing the intrinsic optical properties of the nanotubes.

I will present some of our recent studies which aimed at probing the intrinsic luminescence and absorption properties of chirality identified SWNTs by single molecule microscopies, revealing how environmental effect can affect these properties.

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[1] Cognet et al Science, 316 (2007) 1465 - 1468.

[2] Cognet et al Nanoletters, 8, 2 (2008) 749.

[3] Santos et al, Phys. Rev. Lett., 107 (2011) 187401.

[4] CambrĂŠ, et al, ACS Nano, 6, (2012) 2649.

[5] Crochet et al Nano Letters, 12, 10 (2012) 5091.

[6] Duque et al JACS 135 (2013) 3379.

[7] Oudjedi et al submitted.

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References

Oral Design and development of novel nanoparticles and nanostructured coatings for a wide range of industrial applications

Yolanda R. de Miguel

yolanda.demiguel@tecnalia.com

Sustainable Construction Division, TECNALIA, Parque TecnolĂłgico de Bizkaia, Calle Geldo, Edificio 700, E-48160 Derio â&#x20AC;&#x201C; Bizkaia, Spain

Dr. Yolanda de Miguel from TECNALIA Research & Innovation will present our recent research work on the design and development of novel nanoparticles and nanostructured coatings for a wide range of industrial applications.

In particular, after a brief introduction to Sol-Gel technology and hybrid organic-inorganic chemistry, the lecture will focus on: (1) The synthesis and functionalisation of silicon and titanium oxide nanoparticles with a variety of organic functionalities (e.g. hydroxyl, carboxylic acid, amine, phenyl, vinyl, nitrile groups) and their corresponding characterisation; (2) their applications for the development of novel high performance materials; and finally as an example, (3) the development of novel nanostructured coatings with photocatalytic properties

Figures SiO2

SiO2

NH2

CN

SiO2 50 nm

50 nm

SiO2

SiO2

COOH

50 nm

50 nm

192

50 nm

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Oral Effects of Ga irradiation on the nucleation and propagation of magnetic domain walls in cobalt nanostructures grown by focusedelectron-beam-induced deposition 1

Instituto de Ciencia de Materiales de Aragón (ICMA), Univ. de Zaragoza-CSIC, 50009 Zaragoza, Spain Laboratorio de Microscopías Avanzadas (LMA), INA, Univ. de Zaragoza, 50018 Zaragoza, Spain.

3 TFM Group, Cavendish Lab., Univ. of Cambridge, JJ Thomson Avenue, CB3 0HE, Cambridge, UK 4 Fundación ARAID, 50004 Zaragoza, Spain.

5 Advanced Light Source, Lawrence Berkeley National Laboratory, USA

Jose M. De Teresa

1,2

L. Serrano-Ramón1 A. Fernández-Pacheco3 L. A. Rodríguez2, C, Magén2,4 M. R. Ibarra2, D. Petit3 R.P. Cowburn3 and T. Tyliszczak5

deteresa@unizar.es

2

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the outer 20 nm of the nanowires where the gallium is implanted, especially the grain size, leaving the core of the wire intact. As a consequence, the nucleation field increases rapidly due to an increase in the magnetocrystalline anisotropy at the outer shell at the end of the wires, where the domain walls are formed, while the propagation field, more dependent on the magnetostatic and exchange energy, remains almost constant. In conclusion, Ga irradiation is a powerful method to manipulate domain walls in cobalt nanostructures.

[1] L. Serrano-Ramón et al., ACSnano 5, 7781 (2011).

[2] M. Jafaar et al., Nanoscale Research Letters 6, 407 (2011).

[3] A. Fernández-Pacheco et al., Appl. Phys. Lett.

94, 192509 (2009).

[4] L. A. Rodríguez et al., Appl. Phys. Lett. 102, 022418 (2013).

[5] L. Serrano-Ramón et al., Eur. Phys. J. B, in press; L. Serrano-Ramón et al., submitted.

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References

193

Focused-electron-beam-induced deposition (FEBID) techniques are useful to grow cobalt nanostructures with resolution down to 30 nm [1], with potential applications in magnetic logic, sensing and storage. Magnetic Force Microscopy studies revealed the existence of single-domain magnetic states with appropriate dimensions of the cobalt nanostructures [2]. Magneto-optical Kerr effect (MOKE) measurements identified domain-wall conduit behavior (lower propagation than nucleation fields) in L-shaped nanowires [3].

Lorentz microscopy experiments showed the different types of domain walls appearing in Lshaped nanowires as a function of the cobalt thickness [4]. In the present contribution, we will report recent experiments on the use of Ga irradiation produced by means of a Focused Ion Beam in order to modify the nucleation and propagation of domain walls in cobalt nanostructures grown by FEBID techniques [5].

MOKE and Scanning Transmission X-ray Microscopy (STXM) studies have given evidence for remarkable changes in the nucleation and propagation of domain walls as a function of the Ga irradiation dose. In linear structures with an injection pad [see figure 1(a)], STXM measurements show that Ga doses of the order of 1016 ions/cm2 are required to produce local pinning in the propagation of domain walls. MOKE experiments in L-shaped nanowires indicate that, below 6.4 x 1015 ions/cm2 irradiation, the separation between the nucleation and propagation field increases significantly [see figure 1(b)]. Thus, Ga irradiation results into the enhancement of the operating margin of domainwall-based devices. Transmission Electron Microscopy experiments show that this range of doses modifies significantly the microstructure of

Figures a)

b)

194

Figure 1: (a): Sequence of Scanning Transmission X-ray Microscopy images of the magnetization reversal in one of the cobalt nanowires with local Ga focused-ion-beam irradiation (irradiation dose of 4.48x1016 ions/cm2) in the central part of the wire. (b) Top image: Variation of the nucleation (black) and propagation field (red) of Lshaped cobalt nanowires as a function of the Ga irradiation dose.

The lines are guides to the eye. The three different regimes of irradiation are illustrated by changing the color of the chart: light blue for low irradiation doses, dark blue for medium irradiation doses and pale pink for high irradiation doses; Bottom image: Zoom-in of the first regime of low irradiation doses in the top image.

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Invited Multipod-like Polystyrene/Silica Clusters Designed by Seeded-growth Emulsion Polymerization: Towards Colloidal Molecules and Unconventional Inorganic Nanoparticles 1

ICMCB, CNRS, Univ. Bordeaux, France CBMN, Univ. Bordeaux, CNRS, France C2P2, CPE, CNRS, Univ. Lyon Claude Bernard, France 4 LIONS, IRAMIS CEA, France 5 CRPP, CNRS, Univ. Bordeaux, France

Etienne Duguet

1

Désert1,2, I. Chaduc3, J. Parvole3, A. Komla4, J.C. Taveau2, O. Lambert2, M. Lansalot3, E. Bourgeat-Lami3, A. Thill4, O. Spalla4, L. Belloni4 and S. Ravaine5

duguet@icmcb-bordeaux.cnrs.fr

2 3

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methacrylate) nodule obtained in a second-stage emulsion polymerization, and (iii) showing how PS/silica multipod-like clusters may be derivatised in order to get unconventional nano-objects, e.g. tetrahedron-like and cube-like silica particles, and gold nanocages [6].

This project was supported by the Agence Nationale pour la Recherche (contract # ANR-07BLAN-0271) and the European Community (MetaChem project).

[1] E. Duguet, A. Désert, A. Perro and S. Ravaine, Chem. Soc. Rev. 2011, 40, 941.

[2] A. Perro, E. Duguet, O. Lambert, J. C. Taveau, E. Bourgeat-Lami and S. Ravaine, Angew.

Chem., Int. Ed. 2009, 48, 361.

[3] A. Désert, I. Chaduc, S. Fouilloux, J.C. Taveau, O. Lambert, M. Lansalot, E. Bourgeat-Lami, A. Thill, O. Spalla, S. Ravaine and E. Duguet, Polym. Chem. 2012, 3, 1130.

[4] A. Thill, A. Désert, S. Fouilloux, J.C. Taveau, O. Lambert, M. Lansalot, E. Bourgeat-Lami, O. Spalla, L. Belloni, S. Ravaine and E. Duguet, Langmuir 2012, 28, 11575.

[5] M. Lansalot, I. Chaduc, J. Parvole, E. Duguet, S. Ravaine and E. Bourgeat-Lami, Polym. Chem., 3, 3232 (2012).

[6] To be published soon.

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References

Figures

195

Hybrid organic-inorganic nanoparticles with wellcontrolled morphology are currently of great research interest. Synthetic routes leading to robust aggregates made of nanoparticles of different chemical natures which are associated in a controlled manner, i.e. number of nanoparticles and geometrical arrangement, are especially investigated. Clusters of spheres could mimic the space-filling models of simple molecules and are called “colloidal molecules” [1].

Our strategy is based on a seeded-growth emulsion polymerization process leading to biphasic particles, which are composed of spherical silica spheres (50-400 nm) surrounded by a varying number of polystyrene (PS) nodules (Figure 1) [2].

The hydrophilic surface of the silica seed particles needs to be previously functionalized with methacryloxymethyltrimethoxysilane (MMS). In such conditions, the nucleation/ growth of the PS nodules is highly promoted at the silica surface, leading to multipod-like morphologies (bipods, tetrapods, hexapods, octopods, etc.). While varying different experimental parameters, it was demonstrated that the key parameters to control the pod number and geometrical arrangement are (i) the ratio between the number of silica seeds and the number of growing PS nodules, (ii) the size of silica seeds and (iii) the silane grafting density. A key feature of this strategy is the synthetic process is reproducible, fast and may yield grams of biphasic submicronic particles up to 90% purity [3].

The aim of this communication is to release lastminute results: (i) presenting a model of spheres growing on a sphere to predict the morphology yields of the PS/silica multipod-like clusters [4], (ii) demonstrating the possible synthesis of triphasic clusters with an extra poly(methyl

Invited Combining multiplexed SPRi and AFM approaches for the detection and qualification of circulating blood microparticles sub-populations

Cécile Elie-Caille 2 G. Mourey 1 W. Boireau and P. Saas2

1

caille@femto-st.fr

1 2

Institut FEMTO-ST, CNRS, Université de Franche-Comté, 25044 Besançon, France INSERM/EFS/UFC UMR 1098, 25020 Besançon, France

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In the fields of nanotoxicology and diagnosis, it is of major interest to develop instrumentations or biochips which are able to detect and characterize nano-bio-objects (such as protein complexes, virus, particles...) that are present in various biological samples. Especially, microparticles (MPs) are produced from membrane of every cell types by a process called vesiculation.

Circulating microparticles present in blood samples have emerged as a biological marker in several pathologies. Indeed, an increased concentration of circulating microparticles can be associated with autoimmune diseases or thrombosis. Despite a huge clinical interest, no standard procedures are available for the detection and characterization of blood microparticles, because these biological objects present sizes below the detection limit of conventional methods (< 300nm in diameter). Thus the quantification and qualification of microparticles, that are crucial in various medical fields, require combination of new analytical solutions [1,2]. Among them, Atomic Force Microscopy appears as a powerful technique for size detection and shape determination of particles [3].

Our project consists in developing versatile biochips in arrays allowing both 1) qualifying MPs cellular origin, and then defining their associated functions through surface plasmon resonance analysis (SPRi) and 2) reliable sizing and enumeration of MPs by on-chip AFM investigations. A complete multiplexed study of blood microparticles screening in plasma will be presented, based on arrayed chips, biofunctionalized by natural ligands and antibodies.

Our results of nanosized blood particles exploration and characterization seem to be promising in comparison with usual techniques like

flow cytometry or dynamic light scattering in terms of sensitivity and accuracy.

References [1] E. Van Der Pol, A. G. Hoekstra, A. Sturk, C. Otto, T. G. Van Leeuwen, R. Nieuwland.

Optical and non-optical methods for detection and characterization of microparticles and exosomes. J Thromb Haemost, 2010, 8: 2596– 2607.

[2] Freyssinet J-M, Toti F. Membrane microparticle determination: at least seeing what’s being sized! J Thromb Haemost 2010; 8: 311–4.

[3] Yuana Y, Oosterkamp TH, Bahatyrova S, Ashcroft B, Garcia Rodriguez P, Bertina RM, Osanto S. Atomic force microscopy: a novel approach to the detection of nanosized blood microparticles. J Thromb Haemost, 2010; 8: 315_23.

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Oral Nanoporous gold thin films deposited by magnetron sputtering: tayloring the porosity 1

Instituto de Ciencia de Materiales de Sevilla (CSIC-US), Americo Vespucio 49, 41092 Seville, Spain IMM-Instituto de Microelectrónica de Madrid (CNM-CSIC), Isaac Newton 8, 28760 Tres Cantos, Spain 3 HASYLAB at DESY, Notkestrasse 85, 22603 Hamburg, Germany 4 Departamento de Física Atómica, Molecular y Nuclear, University of Seville, 41071 Seville, Spain

Jose M. García-Martín

2

R. Álvarez1 M. Macías-Montero1 L. Gonzalez-Garcia1 J.C. González1 V. Rico1, J. Perlich3 J. Cotrino1,4 A. R. González-Elipe1 and A. Palmero1

2

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the bulk of the material, and has a very small density of nanopores. ii) ß-type (intermediate σ, low ρg): the film is rather compact, but surface valleys percolate from the very surface of the film to near the substrate through vertical tilted mesopores. This structure could also be seen as a tilted highly coalescent columnar structure (i.e., columns are always touching), whereas mesopores can be devised as the empty space between the coalescent columns. iii) γ-type (high σ, low ρg): The film possesses similarities with the ß-type microstructure, but now surface valleys and mesopores are larger and the columns appear well separated and isolated from each other. For instance, Fig. 2 shows the GISAXS spectra of γ-type films with high σ: the offcenter maxima in Π incidence indicate the existence of individual elements where a clear correlation distance can be determined. iv) δ-like (any σ, high ρg): this film is characterized by vertical coalescent column-like structures, with a high density of nano- and mesopores occluded in the material, and with cavern-like surface patterns elongated in the vertical direction that penetrate deep into the bulk.

With the help of Monte Carlo simulations we have demonstrated that the main structuring mechanisms are the elastic scattering of the gold atoms on plasma heavy particles and the selfshadowing mechanism on the sample surface.

Moreover, particular attention has been paid to the development of geometrical patterns in the bulk of the films as well as to the size and percolation depth of surface valleys, an aspect that has deserved little attention in previous studies in the literature for plasma-assisted depositions of thin films. Overall we have found that some of these nanostructures possess large surface area with high connectivity among nano- and

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Nanoporous gold has attracted much attention in the science and technology for its high catalytic activity towards oxidation reactions, which equals that of gold nanoparticles but avoiding the problems of coarsening with a longer life time. A key element for this functionality is the possibility of synthesizing gold thin films with large surface area with valleys that penetrate deep into the material. Although nanoporous gold has usually been synthesized by chemical dealloying, the possibility of using plasmaassisted deposition techniques is highly desirable, not only because it might allow a better control on the surface and pore percolation features, but also from environmental and industrial points of view. In this context, we have studied the growth of nanoporous gold thin films by magnetron sputtering at room temperature and analyze the percolation depth and connectivity of the pores that penetrate into the film for enhanced catalytic applications [1, 2].

We have deposited gold thin films by magnetron sputtering at oblique angles using a wide range of values of the substrate tilt angle, σ, and the background pressure, ρg. We have analyzed the nanostructure of the obtained films by using different characterization techniques such as Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM) and Grazing Incidence Small-Angle X-ray Scattering (GISAXS).

We have also developed a Monte Carlo growth model, which accurately reproduces the experimental nanostructures. We have found that the whole set of deposited films can be categorized through only four generic nanostructures (see Fig. 1): i) α-type (low σ, low ρg): the film is compact without any well defined geometrical pattern in

jmiguel@imm.cnm.csic.es

mesopores, features that make plasma-assisted techniques an alternative to wet chemistry techniques to synthesize nanoporous gold thin films.

References [1] J.M. Garcia-Martin, R. Alvarez, P. RomeroGomez, A. Cebollada and A. Palmero, Appl.

Phys. Lett. 97, 173103 (2010).

[2] R. Alvarez, J. M. García-Martín, M. MacíasMontero, L. Gonzalez-Garcia, J. C. González, V. Rico, J. Perlich, J. Cotrino, A. R. González-Elipe and A. Palmero, Nanotechnology 24, 045604 (2013).

Figures

Figure 1: The four generic nanostructured Au films obtained by magnetron sputtering at oblique incidence. The “cubes” are simulated films whereas the cross-sections are FESEM images of real samples.

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Figure 2: GISAXS spectra of γ-type films for ∆ and Π incidence: the asymmetric patterns in the latter case indicate the existence of tilted individual nanocolumns.

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Oral Nanosuspension characterization: Application of NTA to research from drug delivery to exosomes research

Roberto Ghiandoni Ben Owen P. Hole P. Vincent A. Siupa and B. Carr

Ben.Owen@nanosight.com

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field of protein aggregation and nanoparticle toxicology.

In the field of toxicology, the ability to measure nanoparticles and to assess the level of aggregation of nanosuspensions dispersed in various media is critical. NTA is appropriate for rapidly measuring samples as the optimal concentration for detection is very low (108 particles/mL) and such samples are commonly polydisperse and has been used extensively to this end [2].

The output, a number-based size distribution and absolute concentration measurements, directly provides the data in the appropriate format.

The technique is also used to directly generate a measure of viral concentration. In this regard, the ability of NTA to determine virus count through direct visualization, is of significant value [3]. It has advantage over both plaque assay (measurement times are of just a few minutes and aggregation can be assessed) and qPCR (as all viral particles will be measured whether or not they contain DNA).

The application with fluorescence filters to allow fluorescently labelled/loaded particles to be selectively analysed can additionally be of particular import where the suspension is not purified.

In the field of pharmaceuticals, a crucial question under inspection is that of protein aggregation and its measurement thereof. In this field NanoSight has been identified as a technique suitable for characterizing this and has crucial benefits over previously available techniques [4].

Here we will present the technique and demonstrate, with examples, how it is a powerful, high resolution multi-parameter method with the capabilities to characterize and monitor particles in both water and biological environments for drug

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NanoParticle Tracking and Analysis (NTA), has been commercially developed over the past six years and now, with over 500 systems installed, is being considered a key characterisation technique in many fields of colloid characterisation particularly in the application of nanomedecines research and development. Here we discuss the technique, its application to nanobiomedecine and how recent developments are further enabling this field.

In this method a laser beam passes through a suspension at a low angle. The particles scatter light which is collected onto a CCD camera by a microscope-type configuration (Fig 1a). Particles, between 10-2000nm, are tracked individually (Fig 1b) and their diffusion coefficient and therefore size calculated directly from their speed (Fig 1c).

This technique gives significant advantage over traditional light scatter techniques (e.g. DLS) as the individual tracking of particles results in a better ability to cope with polydispersed suspension and results in higher resolution [1]. It also generates directly a measure of particle concentration which is critical in understanding many of the applications to which it is applied.

More recently, other parameters have been developed for further characterisation, such as scatter intensity (see figure 2) and zeta potential, all on a particle by particle basis. The technique can be integrated with fluorescence filters to allow fluorescently labelled/loaded particles to be selectively analysed. This allows for more complete characterisation of different nanoparticles within a single sample.

This technique has variously been applied to liposomes and other drug delivery particles, exosomes (with an aim towards a diagnostic measurement), viral vaccines and VLPs and in the

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NanoSight Ltd., Minton Park, Amesbury, SP4 7RT, UK

development and toxicological studies. Data will be shown demonstrating the accuracy and consistency of the technique both in ideal and non-ideal sample types.

References [1] Filipe V, Hawe A, Jiskoot W Pharmaceutical Research, Volume 27, Number 5, (2010) 796810.

[2] http://www.nanosight.com/publications/third -party-papers-/toxicity-and-environment.

[3] Anderson, B., et al. Bacteriophage, Volume 1, Issue 2 (2011), 86-93.

[4] Carpenter, J. F., Randolph, T. W., Jiskoot, W., Crommelin, D. J., Middaugh, C. R. and Winter, G. Journal of Pharmaceutical Sciences, (2010), 99: 2200â&#x20AC;&#x201C;2208.

Figures

Figure 1: a) Scattered light from particles collected on CCD, b) partices tracked and c) size distribution calculated.

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Figure 2: Trimodal measurement of a mixture of 30 and 60nm gold and 100nm latex polystyrene particles. .

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Oral Helium Ion Microscopy. Extending the frontiers of nanotechnology

Carl Zeiss Microscopy Carl Zeiss Str. 56, Oberkochen, Germany

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operate with Ne. The Gas Field Ion Source has been modified and the gun redesigned to allow the use of both He and Ne source gases. Although Best Imaging Voltage (BIV), defined as the optimal voltage to get the highest source brightness, is lower for Ne, the system is optimized to operate under the same column conditions for both gases.

The neon probe size is greater than helium and is measured between 1-2nm although additional improvements are expected. However this is not a limitation from a nanofabrication standpoint. The sputter yield of Ne is about 30X higher than He, and the Ne beam has a shallower penetration depth resulting in lower sub-surface damage. The sputtering of materials with Ne is significantly better than He and generally within a factor 2X of Ga. Neon ion beam has been used for Lithography and is shown to be 1000X more efficient than 30keV electron beam with the ability to print 7nm lines [5]. This work has culminated in the development of an ion microscope with a gas field ion source that can operate with both He and Ne References [1] Smentkowski, V.S., Denault, L., Wark, D., Scipioni, L., and Ferranti, D, Microscopy and Microanalysis 16(Suppl.2), (2010) p.434.

[2] Bell, D. C., Microscopy and Microanalysis 15, (2009), p.147.

[3] Li, W., Wu, W., and Williams, R.S., SPIE Lithography Conference (2012).

[4] Sanford, C.A., Stern, L., Barriss, L., Farkas, L., DiManna, M., Mello, R., Maas, D.J., Alkemade, P.F.A., J. Vac. Sci. Technol. B 27(6), (Nov/Dec 2009), p.2660.

[5] Winston, D., Manfrinato, V.R., Nicaise S.M., Cheong, L.L., Duan, H., Ferranti, D., Marshman,

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peter.gnauck@zeiss.com

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The Helium Ion Microscope has been described as an impact technology offering new insights into the structure and function of nanomaterials [1].

Combining a high brightness Gas Field Ion Source (GFIS) with unique sample interaction dynamics, the helium ion microscope provides images offering unique contrast and complementary information to existing charged particle imaging instruments such as the SEM and TEM [2]. Formed by a single atom at the emitter tip, the helium probe can be focused to below 0.25nm offering the highest recorded resolution for secondary electron images. The small interaction volume between the helium beam and the sample also results in images with stunning surface detail .Besides imaging, the helium ion beam can be used for fabricating nanostructures at the sub-10nm length scale. Researchers have used the helium ion beam for exposing resist and features as small as 4nm have been reported [3]. The main advantage of helium ion lithography over electron beam lithography is the minimal proximity effect [Fig 2,3]. The helium ion beam has also been used for deposition and etching in conjunction with appropriate chemistries [4]. Helium induced deposition results in higher quality deposits than with Ga-FIB or EBID (Electron Beam Induced Deposition). inally, the helium ion beam can be used for direct sputtering of different materials.

Patterning of graphene has resulted in 5nm wide nanoribbons [Fig.1] and 3.5nm holes in silicon nitride membranes have been demonstrated.

However, due to its lower mass, the helium sputter rate is significantly lower than with gallium. Further, helium tends to implant rather than sputter silicon which is an issue for FIB applications in semiconductors. To overcome these issues, we have developed the GFIS to

Peter Gnauck D. Elsiwck M. Ananth, L. Stern J. Notte, L. Scipioni, C. Huynh and D. Ferranti

J., McVey, S., Stern, L., Notte, J., Berggren, K.K., Nano Letters 11(10), (2011), p.4343.

Figures

Figure 1: Fig. 1 Nanoribbons in Graphene (Results courtesy of Dan Pickard NUS).

Figure 2: SEM suffers from proximity effects: Exposed dots near the center are much bigger than the same exposed dots at the corners.

Figure 3: When exposed with a helium beam, the exposed region is smaller, AND more consistent â&#x20AC;&#x201C; independent of nearby exposures.

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(Results courtesy of Karl Bergren of MIT)

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Oral 1

Tractor beams for semiconductor spheres

Raquel Gómez-Medina 1 Y. Zhang 2 M. Nieto-Vesperinas and J. J. Sáenz1,3

1

r.gomezmedina@uam.es

Dpto. Física de la Materia Condensada and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, Campus de Cantoblanco, Madrid 28049, Spain.

2 Instituto de Ciencia de Materiales de Madrid (CSIC), Campus de Cantoblanco, Madrid 28049, Spain.

3 Centro de Investigación en Física de la Materia Condensada (IFIMAC), Universidad Autónoma de Madrid, Campus de Cantoblanco, Madrid 28049, Spain.

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coordinates (ρ,ϕ,z), can be expressed in terms of Bessel functions as where

and TM Bessels beams.

As the angle between the beams increases, the traditional radiation force goes to zero with the cosine of the angle; two counter-propagating waves produce no net radiation pressure force, whereas the contribution to the force coming from the strongly focused forwards scattering remains finite. Above a given angle, the conservation of momentum leads to a total force that points towards the light source.

Because the optical pulling force is strongly related to the existence of interference effects between multipole radiation fields, it is appropriate to investigate the different types and sizes of particle that could be pulled by such a tractor beam.

Researchers recently demonstrated that submicrometre semiconductor spheres are capable of exhibiting dipolar magnetic and electric responses [8]. In these particles, interference between the electric and magnetic dipolar fields can lead to anisotropic angular distributions of scattered intensity, including zero backwards and almost-zero forwards scattering intensities at specific wavelengths [9-10]. As we will show, for a given laser wavelength the pulling force is only possible in specific spectral regimes, because the required interference condition is only obtained for particular ranges of sphere radii, for specific materials and for specific beam configuration. As it

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Equation (1) describes the superposition of phaseshifted TE

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The basic principles of optical manipulation are relatively simple for objects much smaller than the wavelength of incident light. In analogy with electrostatics, small particles develop an electric dipole moment in response to the light’s electric field. By appropriate manipulation of interfering laser beams, it is possible to generate local vortices, complex Poynting vectors and light spin patterns. However, there is no way to accelerate a small particle towards the light source against the photon stream [1, 2].

Larger particles, in contrast, may develop not only electric dipoles, but also magnetic dipoles and higher-order multipoles. The multipole radiation field may present strong interference effects because the excitation is due to the incident coherent electromagnetic field [3]. In particular, interference may cause the radiated field to become strongly focused in the forwards direction (the direction of the incoming beam). This is in contrast with the isotropic radiation pattern of a small electric dipole [4, 5]. Because the total momentum must be conserved, stronger forwards scattering leads to a smaller forwards force. For a highly collimated laser beam (a plane wave), the interference effect on a multipolar particle is not enough to reverse the sign of the radiation pressure force. However, if the projection of the total photon momentum along the propagation direction is small, it is possible to create an attractive optical force that acts against the optical power flow.

Recently, it has been proposed [1,6] and lately demonstrated [7] the use of a Bessel beam for the practical realization of this phenomenon. A Bessel beam can be seen as a combination of plane-wave components whose propagating vectors form a cone that makes an angle θ0 with the propagation axis, i.e. a propagating field, in cylindrical

would not be possible to pull arbitrary particles, we will study the optimal probe that can be pulled by a proposed tractor beam as a function of the beam configuration (see Fig.1). On the other hand, the dependency of this technique on particle size and material nature provides intriguing possibilities for particle sorting. In addition, these particles could be attached to almost transparent objects such as biological macromolecules. The optical pulling force could then be used to attract even transparent objects by using multipolar particles as pulling probes.

Figures

References

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[1] J. J. Sáenz, Nature Photon. 5 (2011) 514-515.

[2] A. Dogariu, S. Sukhov, and J. J. Sáenz, Nature Photonics 7 (2013), 24–27.

[3] M. Nieto-Vesperinas, J. J. Sáenz, R. GómezMedina, and L. Chantada, Opt. Express, 18 (2010) 11428-11443. R. Gómez-Medina, M. Nieto-Vesperinas and J. J. Sáenz, Phys. Rev. A 83 (2011) 033825,1-7.

[4] M. Nieto-Vesperinas, R. Gómez-Medina, and J. J. Sáenz, J. Opt. Soc. Am. A, 28 (2011) 54-60.

[5] R. Gómez-Medina, L. S. Froufe- Pérez, M. Yépez, F. Scheffold, M. Nieto-Vesperinas and J. J. Sáenz, Phys. Rev. A, 85 (2012) 035802.

[6] Chen, J., Ng, J., Lin, Z. and Chan, C. T. Nature Photon. 5, (2011) 531–534. A. Novitsky, C.W. Qiu and A. Lavrinenko, Phys. Rev. Lett. 109 (2012) 023902.

[7] O. Brzobohatý, V. Karásek, M. Šiler, L. Chvátal, T. Cižmár y P. Zemánek. Nature Photonics 7 (2013) 123-127.

[8] A. García-Etxarri, R. Gómez-Medina, L. S. Froufe-Pérez, C. López, L. Chantada, F. Scheffold, J. Aizpurua, M. Nieto-Vesperinas and J. J. Sáenz, Opt. Express, 19 (2011) 48154826.

[9] R. Gómez-Medina, B. García-Cámara, I. SuárezLacalle, F. González, F. Moreno, M. NietoVesperinas and J. J. Sáenz, J. Nanophoton.

5053512 (2011) 1-9.

[10] J. M. Geffrin, B. García-Cámara, R. GómezMedina, P. Albella, L. S. Froufe-Pérez, C. Eyraud, A. Litman, R. Vaillon, F. González, M. Nieto-Vesperinas, J. J. Sáenz, F. Moreno, Nat. Commun. 3 (2012) 1171.

Figure 1: Optical pulling force map of a Silicon probe as a function of the phase shift, ϕ2 -ϕ1, and the y parameter, y=nka . The Bessel beam has characteristics m=1, θ0=900 and |c2|=|c1|. Blue areas correspond to parameter ranges where the pulling force is negative, i.e. optical force acts against the optical power flow.

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Oral 1

Pressure dependence of Raman modes in Graphene Oxide (GO)

Jesus A. Gonzalez 2 R. Valiente 1 F. Rodriguez

1

gonzalezgja@unican.es

DCITIMAC-Malta Consolider Team, Universidad de Cantabria, 39005 Santander, Spain 2 Dto de Física Aplicada- Malta Consolider Team, Universidad de Cantabria, 39005 Santander, Spain

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and the second-order Raman scattering without interference [2] (figure 2). Up to 15 GPa we found a pressure coefficient of 6.2 cm-1 GPa-1 for the tangential G band and 4.1 cm-1 GPa-1 for the D band (figure 3). No pressure-induced structural phase transition was observed in the studied pressure range.

References [1] D. W. Boukhvalov, M. I. Katsnelson, J. Am. Chem. Soc. 130, 10697 (2008).

[2] E. del Corro, M. Taravillo, J. González, V.G. Baonza, Carbon. 49, 973 (2011).

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Figures

Figure 1: Raman spectra of GO at normal pressure.

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GO is a water-soluble nanomaterial prepared through extensive chemical attack of graphite crystals to introduce oxygen-containing defects in the graphite stack. In GO, a large fraction (0.5–0.6) of carbon is sp3 hybridized and covalently bonded with oxygen in form of epoxy and hydroxyl groups.

The remaining carbon is sp2 hybridized and bonded either with neighboring carbon atoms or with oxygen in the form of carboxyl and carbonyl groups, which predominantly decorate the edges of the graphene sheets. GO is therefore a 2D network of sp2 and sp3-bonded atoms, in contrast to an ideal graphene sheet, which consists of 100% sp2-hybridized carbon atoms. This unique atomic and electronic structure of GO, consisting of variable sp2/sp3 fractions, opens up possibilities for new functionalities. The most notable difference between GO and mechanically exfoliated graphene is the optoelectronic properties arising from the presence of a finite band gap [1]. In this work we have used a solution of GO prepared by GRAnPH Nanotech (Spain). The samples are characterized by high resolution transmission electronic microscopy, photoluminescence and Raman spectroscopy. In the Raman spectrum of graphene oxide the G band is broadened and shifted to 1594 cm-1 whereas the D band at 1363 cm-1 becomes the prominent feature in the spectrum indicating the creation of sp3 domains due to the extensive oxidation (see figure 1). The intensity ratio of the D and G bands is a measure of the disorder, as expressed by the sp2/sp3 carbon ratio. In order to investigate their structural stability unpolarized room temperature Raman spectra excited with 514 nm were studied at high pressures. Typical diamond anvils used in high pressure experiments have been substituted by moissanite (6H-SiC) anvils to allow the observation of the D band (around 1360 cm -1)

Figure 2: Raman spectra of GO at different pressures.

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Figure 3: Pressure dependence of D and G bands of GO

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Invited Covalent coupling on surfaces in UHV

André Gourdon

andre.gourdon@cemes.fr The NanoSciences Group, CEMES, CNRS, 29 Rue J. Marvig, Toulouse, France

References

[5] M. Kittelmann, P. Rahe, M. Nimmrich, C. M. Hauke, A. Gourdon, A. Kühnle, ACS Nano 5:10 (2011) 8420–8425.

Figures

Figure 1: Oligomers obtained by coupling of 3,5-diiodosalicylic acid (left) and 2,5-diiodobenzoic acid on calcite

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On-surface covalent coupling of organic precursors to form 0D, 1D, or 2D stable molecules has revealed in the past five years as a potentially powerful way of synthesizing molecular devices difficult or impossible to prepare in solution. So far, this technique has mainly been limited to metallic surfaces or 1ML insulating films on metal, and has allowed for instance to obtain 1D and 2D porphyrin oligomers, nanographene ribbons, polymeric Fe-phthalocyanine single layers and so on [1,2]. Taking into account the recent results in this field, it is now possible to propose coupling mechanisms, and to discuss the potential and limitations of this strategy. For molecular electronics or molecular optics applications, extension of this on-surface coupling technique is also a major objective. We [3] have recently demonstrated [4,5] that, by employing the strong electrostatic interactions between the carboxylate groups of halide-substituted benzoic acids and calcite surfaces, it was possible to reach homolytic cleavage temperatures. This allows for the formation of aryl radicals and intermolecular coupling. By varying the number and position of halide groups, we have obtained linear or zig-zag oligomers.

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[1] A. Gourdon, Angew. Chem., Int. Ed. 47 (2008), 47, 6950–6953.

[2] G. Franc & A. Gourdon, Phys. Chem. Chem.

Phys. 113 (2011) 14283–14292.

[3] Collaboration A. Kühnle's group, Johannes Gutenberg-Universität Mainz (Germany).

[4] M. Kittelmann, P. Rahe, A. Gourdon, A. Kühnle, ACS Nano 6:8 (2012) 7406–7411.

Invited Design of Semi-Metal Nanowire Transistor

Jim Greer L. Ansari and G. Fagas

Tyndall National Institute University College Cork, Lee Maltings, Dyke Parade, Cork, Ireland

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Bandgap engineering in semimetal nanowires can be used to form a field effect transistor (FET) operating on a molecular length scale and eliminates one of the key obstacles to the manufacture of devices below 5 nm: the need for doping in a transistorâ&#x20AC;&#x2122;s source and drain. For sufficiently small wire diameters the metallic behaviour of the semimetal is lost and a bandgap is induced. Using a full quantum mechanical description of the semimetal nanowires, we were able to demonstrate the design of a dopant-free, monomaterial confinement modulated gap transistors (CMGT).

Nanowire FETs enable the continuation of the Mooreâ&#x20AC;&#x2122;s law for future technology generations, by enabling higher device density and consequently high function per integrated circuit at lower unit cost. Critically, use of nanowire transistors permit efficient electrostatic control over charges in the nanowires to allow for low power nanoelectronics, that are now required at the heart of all mobile applications such a smart phones and tablets. For the very small length scales that we consider, even 2 or 3 dopant atoms within the nanowire corresponds to extremely high doping concentration, and since there are only few dopant atoms available, the very concept of a pn junction breaks down. Recently, the introduction of a single carrier type in the source, channel, and drain regions of nanowire-like structures led to the demonstration of junctionless nanowire transistors (JNTs) [1]. This design offers one of the few competitive solutions to engineer out difficulties related to aggressive scaling of the traditional (bulk or nano-engineered) MOSFETs; physical operation of these transistors with a gate length as small as 3 nm has been theoretically and experimentally studied [2,3]. In JNTs, variability issues due to the

formation of pn junctions are avoided. For channels with sub-5 nm lengths, the number of semiconductor atoms in the channel and source/drain regions for semiconductor nanowires is typically on the order of a few hundred to thousand and introduction of even a few dopant atoms introduces extremely high doping levels.

Another limitation at this length scale arises the decoupling of dopant levels from the energy bands (due to confinement) which suppresses dopant activation [2,4].

Difficulties with the doping of nanowire structures and the drawbacks associated with energy bandgaps increasing with decreasing diameter can be avoided. Using a full quantum mechanical description of the semimetal nanowires, it is demonstrated that on the length scale on which a semimetal-semiconductor transition occurs, bandgap engineering allows for the formation of a field-effect transistor while eliminating the need for doping. The resulting proposal for a transistor design, the confinement modulated gap transistor (CMGT), follows by forming the source, channel and drain regions using atoms of a single element, unlike in conventional MOSFETs which require dopant atoms to define different device regions.

The electronic and electrical properties of the channel are engineered by varying the nanowire cross-section to achieve modulation of the bang gap energy along the wireâ&#x20AC;&#x2122;s axis. This creates metallic source and drain regions and a semiconducting channel. For the length scales we are interested in, we demonstrate this is readily achievable using semimetal nanowires.

The model CMGT is compromised of 1 nm diameter SnNW and physical gate length of Lg = 2.3 nm. It should be noted that the physical channel length in the off-state is approximately 4.1 nm as

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estimated from the local density of states. The oxide isolating the channel from the gate electrode is modelled as a continuum characterised by 1 nm hafnium oxide thickness and a dielectric constant of ~ 25. Note these dimensions were chosen for computational ease, and similar device structures at larger critical dimensions with different wire orientations and materials can be achieved.

The predicted current-voltage characteristics from ab initio simulation are shown in figure 2, with the prediction of extremely good turn-off characteristics in a gate-all-around configuration [5].

Acknowledgments: This research is funded by Science Foundation Ireland under the Principal Investigator Grant No. 06/IN.1/I857. We thank the SFI/HEA Irish Centre for High-End Computing (ICHEC) for the provision of computational facilities and support

Figures

Figure 1: Atomic scale illustration of CMGT implemented using Îątin. The ring around the channel region indicates an isopotential surface due to the applied gate bias.

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[1] J. P. Colinge et. al., Nature Nanotechnology, 5, 3, p. 225, (2010).

[2] L. Ansari, B. Feldman, G. Fagas, J.-P. Colinge, and J. Greer, Applied Physics Letters, 97, 6, p.

062105, (2010).

[3] S. Migita, Y. Morita, M. Masahara, and H. Ota, International Electron Devices Meeting (IEDM), San Francisco, p. 191, (2012).

[4] R. Rurali, B.Aradi, T. Frauenheim, and A. Gali, Phys. Rev. B , 79, p. 115303, (2009).

[5] L. Ansari, G. Fagas, J.-P. Colinge and J.C. Greer, Nano Letters, 12, 2222 (2012).

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References

Oral Nucleation of the electroactive ß-phase, dielectric and magnetic response of poly (vinylidene fluoride) composites with Fe2 O3 nanoparticles

Jon Gutiérrez

1

A. Lasheras1 J.M. Barandiarán1 R. Gonçalves2,3 P.M. Martins2 C. Caparrós2 M. Benelmekki2 G. Botelho3 and S Lanceros-Mendez2,4

1

Departamento de Electricidad y Electrónica, Facultad de Ciencia y Tecnología, Universidad del País Vasco UPV/EHU, P. Box 644, E-48080, Bilbao, España 2 3 Departamento de Física Departamento de Química da Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal 4 INL-International Iberian Nanotechnology Laboratory, 4715-330 Braga, Portugal

210

We present the synthesis of iron oxide magnetic nanoparticles (IOMNPs) and their inclusion in a poly (vinylidene fluoride) (PVDF) matrix with the objective to produce IOMNPs/PVDF multiferroic nanocomposites [1]. A co-precipitation technique was used to produce IOMNPs with an average size distribution of the order of the 15 nm of diameter.

These IOMNPs were studied and characterized by Xray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM) (see Fig. 1).

IOMNPs/PVDF composites were prepared by a solution method and melt crystallization crystallize in the electroactive phase of the polymer, being the ß-phase fraction proportional to the ferrite content. Increasing concentration of the IOMNPs nucleates the piezoelectric ß-phase of the polymer, decreases the degree of crystallinity and increases the melting temperature of the polymer matrix leading to electroactive materials with large potential for sensor and actuator applications. The crystallization of this phase is attributed to electrostatic interactions of the polymer chains with the nanoparticles. The room temperature dielectric constant and the melting temperature of the nanocomposites increase with increasing IOMNP content, whereas the degree of crystallinity and the a.c. conductivity decrease (see Fig. 2). The slight decrease of the a.c. conductivity of composites respect to the pure PVDF polymer (this difference being larger for lower frequencies) is attributed to the lower ionic mobility within the polymer matrix due to charge trapping around nanoparticles, mainly due to strong interfacial interactions.

Both missing coercivity and the shape of the hysteresis loop represent an evidence for quasisuperparamagnetic behavior for room

jon.gutierrez@ehu.es

IOMNPs/PVDF composites (see Fig. 3). That behavior is also evidenced from the FC and ZFC dependences of the magnetization vs. temperature. From those ZFC – FC measurements it is also inferred that the nanoparticles inside the polymeric matrix behave as magnetic monodomains. The overall electrical and magnetic characteristics of the IOMNPs/PVDF nanocomposites lead to materials with large potential for sensor and actuator applications.

References [1] R. Gonçalves, P.M. Martins, C. Caparrós, P. Martins, M. Benelmekki, G. Botelho, S LancerosMendez, A. Lasheras, J. Gutiérrez and J.M. Barandiarán, Journal of Non-Crystalline Solids, 361 (2013) 93-99, and references therein.

Figures

Figure 1: Nanoparticle characterization by (a) X-ray diffraction, (b) DLS and (c) and (d) TEM. at different frequencies.

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Figure 2: Conductivity obtained for the different IOMNP content on nanocomposite films, at different frequencies.

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Figure 3: (a) ZFCâ&#x20AC;&#x201C;FC low field (100 Oe) magnetization curves for IOMNP/PVDF 5%w/w nanocomposite. (b) Room temperature hysteresis for IOMNP/PVDF nanocomposites with different ferrite contents

Invited Advances in NEMS MASS Spectrometry in the LETI/CALTECH ALLIANCE

SĂŠbastien Hentz

sebastien.hentz@cea.fr CEA, LETI, MINATEC campus, 17 rue des martyrs, 38054 GRENOBLE Cedex 9, France.

Nano Electro Mechanical Systems (NEMS)-based Mass Spectrometry (MS) holds great promise for point of care applications or air quality monitoring.

NEMS mass sensing is performed by monitoring the mass-induced frequency shift of the device in real time. The mass distribution of particles in a mixture can be analyzed if those particles are sent onto the NEMS. NEMS-MS is a new paradigm for high-throughput biological MS with singlemolecule level. The significant opportunity of NEMS-MS originates from its combined attributes of mass resolution, compactness and, especially, scalability: the latter can potentially yield extremely fast measurements and the possibility to perform such measurements using a handheld device. Recent advances in the field, obtained by joint efforts from Prof. Roukes group at Caltech and the NEMS group at LETI will be presented.

Demonstration of the first real-time, single-protein NEMS-MS spectrum of IgM antibody will be described. Compared measurements with conventional MS will be discussed, as well as first efforts towards scaling up the technolog

References

212

[1] M.S. Hanay et al, Nature Nanotechnology, vol.7, pp. 602-608, 2012.

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Oral 2

Development of a novel method for the identification of mouse gastric stem cells Using Raman Spectroscopy

Ali Hilal Alnaqbi 1 R. Alkhatib 3 M. Al-Rubeai S. M Karam1

1

alihilal@uaeu.ac.ae

Department of Anatomy, College of Medicine and Health Sciences, Email:skaram@uaeu.ac.ae 2 Department of Mechanical Engineering,College of Engineering; United Arab Emirates University, Al Ain, United Arab Emirates. Email:alihilal@uaeu.ac.ae 3 School of Chemical and Bioprocess Engineering, University College Dublin, Dublin 4, Ireland Email:m.al-rubeai@ucd.ie

Figures

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Figure 1: 60nm 20%, GNP inside cytoplasm, GNP tend to aggregate inside cell in vesicles.

References [1] Sathuluri RR, Yoshikawa H, Shimizu E, Saito M, Tamiya E (2011) PLoS ONE 6(8): e22802.

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Figure 2: Picogreen cell proliferation assay (Concentration).

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The stomach is lined by different types of epithelial cells which are generated continuously by gastric stem (GS) cells. These cells are rare and difficult to identify. Previous reports demonstrated the use of gold nanoparticle-based surface-enhanced Raman scattering (SERS) for probing the differentiation of embryonic stem cells (1). As a first step to use SERS as a tool to identify and characterize GS cells we tested the effect of gold nanoparticles (GNP) on growth and viability of GS cells. Trypsinized mouse GS cells were incubated with GNP either directly or after forming embryoid bodies using the hanging drop method. Transmission electron microscopy (TEM) was used to localize GNP inside cells, whereas PicoGreen assay were used to measure cell proliferation. Neutral red uptake (NRU) assay was used to test GNP cytotoxicity. TEM confirmed the intracellular localization of GNP. PicoGreen assay showed that the number of GS cells treated with GNP increased by 32.8% within 3 days in comparison to untreated cells. Additionally, NRU assay showed that GNPs have no toxic effect on GS cells. We are currently employing SERS to identify and characterize GS cells.

Invited Electric Field Tuned Topological Insulator

Xiao Hu Q. -F. Liang and L. -H. Wu

WPI-MANA, NIMS, Tsukuba 305-0044, Japan

Hu.Xiao@nims.go.jp

214

A topological state with simultaneous nonzero charge and spin Chern numbers is possible for electrons on honeycomb lattice based on band engineering by staggered electric potential and antiferromagnetic exchange field in presence of intrinsic spin-orbit coupling. With first principles calculation we confirm that the scheme can be realized by material modification in perovskite Gtype antiferromagnetic insulators grown along [111] direction, where d electrons hop on a single buckled honeycomb lattice. This material is ideal for spintronics applications, since a finite sample provides a spin-polarized quantized edge current, robust to both nonmagnetic and magnetic defects, with the spin polarization tunable by inverting electric field [1]. The total magnetization is compensated to zero, and thus the system can be considered as a half-metallic antiferromagnet [2].

Topology becomes the central concept in condensed matter physics. The breakthrough took place when Kane and Mele clarified that electrons on graphene, a two-dimensional honeycomb lattice of carbon atoms, open a gap by spin-orbit coupling (SOC) and achieve a topologically nontrivial state called quantum spin Hall effect (QSHE) [3]. This discovery triggers a huge amount of activities in exploring topological states and materials.

As the common home base for both Kane-Mele model [3] and the spinless Haldane model, honeycomb lattice serves a unique role in understanding the topological property of electron systems [4]. It may be illustrative to summarize its electronic structure paying attention to the Berry curvature configuration. There are two sites in the unit cell of honeycomb structure. With nearest neighbor hopping, electronic valance and conduction bands touch linearly and thus form

Dirac cones at two inequivalent k points, K and K', locating at the corners of Brillouin zone. It is important to observe that Bloch wave functions exhibit opposite chiral features around K and K', characterized by opposite Berry curvatures (see Fig. 1), which establishes the special position of honeycomb lattice in exploring topological state.

By using spin-orbit coupling, the antiferromagnetic exchange field and the staggered electric potential, we can reverse the Berry curvature at Kâ&#x20AC;&#x2122; in only one spin channel, resulting in a topological state characterized by simultaneous nonzero charge and spin Chern numbers [1,5]. The band engineering is based on a full control on the degrees of freedom of spin, valley and sublattice. Since the staggered magnetic field can be realized by antiferromagnetic (AFM) insulators, compact and stable devices based on the topological state in Fig. 2(e) are possible as compared with the photoassisted scheme [5].

As material realization of our idea, we focus on delectron systems in perovskite structure. First, we choose a perovskite insulator ABO3 with G-type AFM order on the magnetic B atoms. Along [111] direction B atoms form a stacking of buckled honeycomb lattice, which can be grown by cuttingedge molecular beam epitaxy (MBE) with atomic precision. During the growing process, a single buckled honeycomb layer of B atoms is replaced by that of nonmagnetic B' atoms, where the element B' is chosen conjugate to B in order to form a d8 configuration. For B'-d electrons on the single buckled honeycomb lattice, intrinsic SOC becomes sizable, a uniform electric field induces a staggered electric potential for the two sublattices, and the G-type AFM order on B atoms on the two sides provides an AFM exchange field. The material design makes the magnetic field of pure exchange

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character, which avoids possible stray field from permanent ferromagnet. We have checked successfully our idea by performing first principles calculations for several materials. In transition metal perovskites we found intrinsic SOC of several tens of meV, which is larger than that in silicene in magnitude by one order, and makes the new topological state available at room temperature.

References [1] Liang Q F, Wu L H and Hu X, submitted (2013) (arXiv.1301.4113).

[2] Hu X, Adv. Mater. 24 (2012) 294.

[3] Kane C L and Mele E J, Phys. Rev. Lett. 95 (2005) 226801.

[4] Haldane F D M, Phys. Rev. Lett. 61 (1988) 2015.

[5] Ezawa M, Phys. Rev. Lett. 110 (2013) 026603.

Figure 1: Dirac cones and merons of effective magnetic field for electrons on honeycomb lattice.

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Figures

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Figure 2: Possible configurations of Berry curvatures for electrons on honeycomb lattice [1]: (a) pristine honeycomb lattice under staggered electric potential; (b) QSHE; (c) SDW; (d) QAHE; (e) novel topological insulator state addressed in the present talk [1,5].

Invited Reversible optical doping of graphene

1

Laboratoire Charles Coulomb. Université Montpellier 2 – CNRS, Place Eugène Bataillon, 34095, Montpellier cedex 05, France 2 CEMES - CNRS – Université de Toulouse, 29 rue Jeanne Marvig, 31055, France

Jean-Roch Huntzinger

1

A. Tiberj1, M. Rubio-Roy2 M. Paillet1, P. Landois1 M. Mikolasek 1, S. Contreras1 J. - L. Sauvajol1, E. Dujardin2 and A. Azmi Zahab1

Antoine.Tiberj@univ-montp2.fr

216

The ultimate surface exposure provided by graphene monolayer makes it the ideal sensor platform but also exposes its intrinsic properties to any environmental perturbations. We show in this work that structural and electronic characterization of graphene in air by Raman spectroscopy is significantly affected by the substrate surface cleaning method and moderate laser power conditions. In particular, we demonstrate that the charge carrier density of graphene exfoliated on a SiO2/Si substrate can be finely and reversibly tuned between electron and hole doping with visible photons. The amplitude of this photo-induced doping is found to require hydrophilic substrates and to vanish in suspended graphene. These findings suggest that optically gated graphene devices operating with a subsecond time scale can be envisioned but also that Raman spectroscopy might not be as non-invasive as generally assumed.

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Oral A spray-drying strategy for synthesis of nanoscale metal–organic frameworks and their assembly into hollow superstructures

1

Inhar Imaz 1 A. Carné 1 M. Cano D. Maspoch1,2 inhar.imaz@icn.cat, daniel.maspoch@icn.cat

1

CIN2 (ICN-CSIC), Catalan Institute of Nanotechnology, Esfera UAB, 08193 Bellaterra, Spain 2 Institució Catalana de Recerca i Estudis Avançats (ICREA), 08100 Barcelona, Spain

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References [1] A. Carné, C. Carbonell, I. Imaz, D. Maspoch, Chem. Soc. Rev. 2011, 40, 291.

[2] A. Carné, I. Imaz, M. Cano-Sarabia, D. Maspoch, Nature Chemistry 2013, DOI: 10.1038/NCHEM.1569.

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MIL-88A, 43 MIL-88B, MOF-14, MOF-74 [M = Zn(II), Ni(II) and Mg(II)], UiO-66, ZIF-8, Prussian blue analogues, MOF-5 and IRMOF-3), drastically reduces their production times and costs, and enables continuous and scalable nanoMOF synthesis as well as solvent recovery. Furthermore, this spray-drying strategy also enables the construction of MOF superstructures comprising multiple nanoMOFs assembled together, and the encapsulation of guest species, such as fluorescent dyes and inorganic nanoparticles, within these superstructures. We anticipate that this will provide new routes to capsules, reactors, composite materials, an1d advanced adsorbents.

As a first proof-of-concept, we show how the entrapment of magnetic nanoparticles within hollow HKUST-1 superstructures results in advanced adsorbents that can be used for magnetic solid-phase removal of the organosulfur dibenzothiophene (DBT) fuel contaminant.

217

Miniaturization to the nanometer scale regime is a very prolific strategy for the development of new materials with novel and often enhanced properties compared to traditional materials. In such a context, nanoscale Metal-Organic Frameworks (also known as nanoMOFs) can also show size-dependent properties that are expected to expand the scope of MOFs in numerous practical applications, including drug-delivery, contrast agents, sensor technology and functional membranes and thin-films, while opening up novel avenues to more traditional storage, separation and catalysis applications and to functional selfassembled MOF superstructures of higher complexity [1]. Today, the growing interest in nanoMOFs demands advanced, low-cost and scalable methodologies for their general synthesis and self-assembly. This is crucial if one wants to start imaging their use for practical applications in a near future.

Herein, we show that spray-drying technique can be exploited as a general, low-cost, rapid and scalable method for the synthesis and selfassembly of nanoMOFs [2]. It enables massive production of sub-5 μm hollow, spherical MOF superstructures from the localized crystallization of nanoMOFs on the surfaces of atomized droplets of a MOF precursor solution upon heating (Fig. 1).

In this method, the atomized droplets produced in spray-drying are used as individual reactors to confine the fast synthesis and assembly of nanoMOFs at a large scale. The resulting superstructures are robust and, following disassembly via sonication, afford well-dispersed, discrete nanoMOFs (Fig. 2).

Importantly, this strategy is applicable to a broad range of MOFs that covers most known porous MOF subfamilies (HKUST-1, Cu-bdc, NOTT-100,

Figures

Figure 1: Hollow MOF superstructures obtained by spray-drying.

218

Figure 2: a, Schematic showing the disassembly of the HKUST-1 superstructures upon sonication to form well-dispersed, discrete nanoHKUST-1 crystals. b, Representative FESEM and TEM (insets) images of the HKUST-1 superstructures (b) and corresponding disassembled nanoHKUST-1 crystals (c).

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Invited Silicon and Germanium spintronics 1

INAC/SP2M, CEA and Université Joseph Fourier, F-38054 Grenoble, France Unité Mixte de Physique, CNRS and Thalès, F-91767 Palaiseau, France LETI, CEA Minatec Campus, F-38054 Grenoble, France 4 INAC/SCIB, CEA and Université Joseph Fourier, F-38054 Grenoble, France 2

Matthieu Jamet

1

A. Jain1, J.-C. Rojas Sanchez1 M. Cubukcu1, J. Peiro2 J.-C. Le Breton2, C. Vergnaud1 E. Augendre3, L. Vila1 J.-P. Attané1, S. Gambarelli4 H. Jaffrès2 and J.-M. George2

3

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CoFeB we could thermally induce a spin accumulation in Ge due to the tunnelling spin Seebeck effect [10,11].

[1] D. D. Awschalom, D. D. Flatté, Nature Phys. 3, (2007) 153-159.

[2] I. Zutic, J. Fabian, S. Das Sarma, Rev. Mod. Phys. 76, (2004) 323-410.

[3] S. Datta and B. Das, Appl. Phys. Lett. 56, (1990) 665–667.

[4] A. Fert and H. Jaffrès, Phys. Rev. B 64, (2001) 184420-184428.

[5] M. Tran, H. Jaffrès, C. Deranlot, J.-M. George, A. Fert, A. Miard, A. Lemaitre, Phys. Rev. Lett.

102, (2009) 036601-036604.

[6] S. P. Dash, S. Sharma, R. S. Patel, M. P. de Jong, R. Jansen, Nature 462, (2009) 491-494.

[7] A. Jain, L. Louahadj, J. Peiro, J.-C. Le Breton, C. Vergnaud, A. Barski, C. Beigné, L. Notin, A. Marty, V. Baltz, S. Auffret, E. Augendre, H. Jaffrès, J.-M. George, M. Jamet, Appl. Phys.

Lett. 99, (2011) 162102-162105.

[8] A. Jain, J.-C. Rojas-Sanchez, M. Cubukcu, J. Peiro, J.-C. Le Breton, C. Vergnaud, E. Augendre, L. Vila, J.-P. Attané, S. Gambarelli, H. Jaffrès, J.-M. George, M. Jamet, to appear in Eur. Phys. J. B (2013).

[9] A. Jain, J.-C. Rojas-Sanchez, M. Cubukcu, J. Peiro, J.-C. Le Breton, E. Prestat, C. Vergnaud, L. Louahadj, C. Portemont, C. Ducruet, V. Baltz, A. Barski, P. Bayle-Guillemaud, L. Vila, J.-P. Attané, E. Augendre, G. Desfonds, S. Gambarelli, H. Jaffrès, J.-M. George, M. Jamet, Phys. Rev. Lett. 109, (2012) 106603-106607.

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References

219

In this presentation, I will first review the recent advances in silicon and germanium spintronics.

This field of research aims at combining the carrier charge and spin in the same device made of silicon and germanium in order to add new functionalities to nowadays microelectronic devices [1,2]. The first proposal for a semiconductor-based spintronic device was made in 1990 by Datta and Das: they introduced the concept of spin transistor [3]. Since then, huge effort has been devoted to succeed in the very first step to the development of such a device: electrical spin injection in semiconductors.

Indeed many obstacles had to be overcome before creating a non-equilibrium spin population into Si or Ge conduction or valence bands [4]. In this talk, I will discuss about these different issues and show how we could circumvent most of them to achieve spin injection in n-Si and n-Ge at room temperature. In particular, we clarify the exact role of interface states in the spin injection mechanism [5,6,7] and show a clear transition from spin accumulation into interface states to spin injection in the Si and Ge conduction bands. For this purpose, we have grown a CoFeB/MgO spin injector on Silicon-On-Insulator (SOI) and Germanium-On-Insulator (GOI). We observe a spin signal amplification at low temperature due to spin accumulation into interface states [8,9]. At 150 K, we find a clear transition to spin injection in the channel up to room temperature: the spin signal is reduced down to a value compatible with spin diffusion model. In this regime, we could also demonstrate the spin signal modulation by applying a back gate voltage and by spin-pumping at the ferromagnetic resonance of the CoFeB layer which are clear manifestations of spin accumulation in the Si and Ge channels. Finally by setting a temperature difference between Ge and

matthieu.jamet@cea.fr

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[10] J.-C. Le Breton, S. Sharma, H. Saito, S. Yuasa and R. Jansen, Nature 475, (2012) 82.

[11] A. Jain, C. Vergnaud, J. Peiro, J.-C. Le Breton, E. Prestat, L. Louahadj, C. Portemont, C. Ducruet, V. Baltz, A. Marty, A. Barski, P. BayleGuillemaud, L. Vila, J.-P. Attané, E. Augendre, H. Jaffrès, J.- M. George, M. Jamet, Appl. Phys.

Lett. 101, (2012) 022402-022405.

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Haïk Jamgotchian B. Aufray B. Ealet and J.-P. Bibérian

CINaM, CNRS, Aix-Marseille Université, Campus de Luminy, Case 913, 13288, Marseille Cedex 9, France

jamgotchian@cinam.univ-mrs.fr

For the past three years many groups around the world work intensively to achieve the synthesis of silicene which is a new crystalline form of silicon i.e. a single atomic layer of silicon with a honeycomb atomic structure like graphene. Many theoretical calculations using ab initio or tight binding approach have shown that this new allotropic form of silicon (flat or weakly buckled) has an intrinsic stability with electronic properties almost identical to those graphene. In particular, π * and π bands of the band structure form a Dirac cone at the K points of the Brillouin zone.

Compared to graphene, the low overlap between the pz orbital makes silicene probably less stable but more reactive to the surface adsorption of foreign chemical species and therefore, all applications currently envisaged with graphene, could be shifted to this new material with the advantage of being easily transferable to the electronics industry which is essentially based on silicon [1]. From an experimental point of view, the first work showing a silicon layer with a 2D honeycomb structure suggesting a possible formation of silicene were made in Marseille (CNRS-CINAM) by thermal silicon deposition on (110) (100) and (111) Ag surfaces. Today despite the number of publications in the field, the atomic structure of silicene grown on this substrate is still under debate because none of these works have defined exactly its intrinsic structure.

For Si/Ag(110), the first steps (<1ML) of silicon growth at room temperature (RT) reveal the formation of silicon nano-ribbons (NRs) [2], all parallel along the [-110] direction of silver, with perfect order. At slightly higher temperatures these unique 1D silicon NRs self-assemble to form a grating with a periodicity of 2.03 nm covering the entire substrate surface and giving rise to a (5×2) superstructure [3] (Figure 1a). STM images reveal a

honeycomb arrangement (Figure 1b)[4] which have been confirmed within DFT-GGA calculation.

The NR’s may consist in slightly arch-shaped graphene-like stripes formed by a honeycomb structure, as seen in figure 1c [5]. All these results seems to show that silicon NRs grown on Ag(110) present a graphite-like structure which could be true silicene. Unfortunately, the knowledge of the Si-Si bond distance, which would definitively confirm the atomic structure, is still missing. At higher coverage (> 1 ML) one observes the formation of nano-ribbons with a pyramidal shape which could be a stack of silicene layers (Figure 1d) [6].

On Ag(111) face, the deposition of one monolayer gives rise to different superstructures (4x4), √13x√13)R13.9°, (2√3x2√3)R30° and (√7x√7)R19.1° which are strongly correlated to the growth onditions (substrate temperature and deposition rate)[7]. All these superstructures (and thecorresponding STM images) can be explained by the same silicon mono layer (silicene ?) only rotated relative to the silver substrate (Figure 2A).

The STM image topographies can be explained by the relative position of silicon atoms in relation to the silver atoms (yellow atoms on the figure 2A).

Shortly after this observation, all these superstructures have been more or less confirmed by different groups [8,9] but with other structural models [8]. Note that there is still a large controversy concerning the (2√3x2√3)R30° superstructure since it is not always observed [10,11]. Finally like on the (110) face, at higher coverages one observes by LEED and by STM (Figure 2B), a new super-structure which could be the signature of the growth of a second silicene layer.

On this (111) face, as well as the (110) face the question of the atomic structure is still open and

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Synthesis and properties of Silicene layers on metallic substrates

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Invited

only an accurate measurement of the Si-Si distance could clarify the situation.

In this presentation after a recall of the main results obtained in this field we will present our recent measurements of the Si-Si interatomic distances obtained on both faces by EXAFS

References [1] A. Kara, et al, Surface Science Reports 67 (2012) 1.

[2] C. Leandri, et al, Surface Science 574 (2005) L9.

[3] H. Sahaf, L. Masson, C. Léandri, B. Aufray, G. Le Lay, F. Ronci, Applied Physics Letters 90 (2007) 263110.

[4] B. Aufray, et al, Applied Physics Letters 96 (2010) 183102.

[5] A. Kara, et al, Journal of Superconductivity and Novel Magnetism 22 (2009) 259.

[6] P. De Padova, et al,, Nano Letters 12 (2012) 5500.

[7] H. Jamgotchian, et al, Journal Of PhysicsCondensed Matter 24 (2012).

[8] B. Feng, Z. Ding, S. Meng, Y. Yao, X. He, P. Cheng, L. Chen, K. Wu, Nano Letters 12 (2012) 3507.

[9] P. Vogt, et al, Physical Review Letters 108 (2012) 155501.

[10] C.-L. Lin, et al, Applied Physics Express 5 (2012).

[11] R. Arafune, et al, Surface Science 608 (2012) 297.

Figure 2: A) Ball models of one silicon monolayer on top of a Ag(111) surface (inserted are the corresponding STM images). α is the angle of rotation of the silicon layer relatively to silver. a) (4x4) superstructure; b) (2√3x2√3)R30° superstructure; c) (√13x√13)R13.9° superstructure type I; d) (√13x√13)R13.9° superstructure type II and e) (√7x√7)R19.1° superstructures (expected but not observed). B) Filled state STM image (12x9 nm2) of the surface of the silicene second layer.

Figures

222

Figure 1: a) Filled states STM image (24 nm)2 of the surface at full coverage showing silicon nanoribbons on Ag(110) surface and the corresponding (5x2) LEED pattern, b) Filled states high resolution STM image; c) corresponding ball model of the calculated atomic structure, d) stack of silicene nano ribbons.

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Oral Advances in Quantitative Impedance Measurement and Dopant Level Profiling Using Scanning Microwave Microscopy

1

Gerald Kada 1 Shijie Wu 2 M. Moertelmaier F. Kienberger2 and 3 H. Tanbakuchi

Shijie_wu@agilent.com 1

Agilent Technologies, Inc., Chandler, AZ, USA Agilent Technologies Austria GmbH, Measurement Research Lab, Gruberstrasse, Linz 3 Agilent Technologies, Inc., Santa Rosa, CA 2

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against known dopant structures such as that fabricated by IMEC.

References [1] H. P. Huber, M. Moertelmaier, T. M. Wallis, C. J. Chiang, M. Hochleitner, A. Imtiaz, Y. J. Oh, K. Schilcher, M. Dieudonne, J. Smoliner,P. Hinterdorfer,S. J. Rosner, H. Tanbakuchi, P. Kabos, and F. Kienberger, Rev. Sci. Instrum. 81 (2010)113701.

[2] Shijie Wu and Jing-Jiang Yu, Appl. Phys. Lett.

97 (2010)202902.

[3] J. Hoffmann, M. Wollensack, M. Zeier, J Niegemann, Hans-Peter Huber and F. Kienberger, 12th IEEE International Conference on Nanotechnology (IEEE- NANO).

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Figures

Figure 1: SMM imaging of eeprom cells with different DC bias applied.

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Scanning microwave microscopy (SMM) is a recent development in SPM technique that combines the lateral resolution of AFM and the measurement precision of microwave analysis. It consists of an AFM interfaced with a vector network analyzer (VAN). In the reflection mode (S11 measurement), the measured complex reflection coefficient of the microwave from the contact point directly correlates to the impedance of the sample under test. A linear calibration procedure for SMM using a capacitance standard has been developed and used to measure the minute capacitance difference, such as that between decanethiol and octadecanthiol SAM layers [1,2]. However, the linear calibration procedure is limited to a small impedance range. A nonlinear calibration algorithm that works on all measurement objects has been developed recently [3]. The new algorithm is valid for the measurement of quantitative complex impedance, and has means to discriminate between lossy and capacitive components. Results from electromagnetic simulation of the complex impedance at the tip/sample interface using EMPro will be presented as well. The capability of measuring the capacitance of a doped structure directly poses a unique advantage for SMM over the existing scanning capacitance microscopy technique. A high throughput C-V mapping workflow, Scanning Sawtooth C-V Spectroscopy (SSCV), was also established. This allows for nanoscale mapping of C-V curves for materials science applications.

Based on capacitance measurement, SMM can be used for doping structure characterization of semiconductor devices see Figure 1. Quantitative dopant concentration can be obtained by calibrating the measured capacitance, C, or dC/dV

Oral DFT Studies of One-Dimensional Systems of Metal-porphyrin Tapes and CuCN Nanowires

Hong Seok Kang

hsk@jj.ac.kr

Department of Nano & Advanced Materials, Jeonju University, Hyoja-dong, Wansan-ku, Chonju, Chonbuk 560-759, South Korea

Based on the calculation using the density functional theory, we have investigated the electronic structures of one-dimensional (1D) metal-porphyrin tapes (M-PPT), where M is a metal atom in 3d series.[1] Depending upon the kind of M atom, we first find that M-PPT exhibits varierty of electric properties from a semiconductor to a metal, and even to a halfmetal. The band gap is either direct or indirect depending upon the system. Second, our calculation of the quantum transport properties indicate that the bilayer formation of armchair graphene nanoribbons (GNRs) with Zn-PPT or RuPPT shows that the bilayer exhibits different conducting properties depending upon the method of inter-unit linkage.[2,3] Third, a ladder type double-stranded 1D system of Zn-PPT bridged by a bypyridyl group (BPY), which was recently synthesized[4], is shown to exhibit a giant Stark effect under the transverse electric field.[5] The effect is as large as that in the boron nitride nanotubes (BNNTs). Fourth, we have also investigated the electronic and magnetic properties of 1D systems of the BPY with M (= Li, V, or Ti) atoms. [6] We find that the difference in the magnetic properties can be understood in terms of different strength of M-M interaction.

Finally, hexagonal AuCN or CuCN crytals and their nanowires are shown to have a very high Li storage capacity. Surprisingly, we observe no appreciable volume change after Li is intercalated among three AuCN or CuCN chains with the stoichiometry of AuCN-Li or CuCN-Li. [7].

[2] H. S. Kang and Y.-S. Kim, J. Phys. Chem. C 116 (2012) 8167.

[3] H. S. Kang, Chem. Phys. 405 (2012) 148.

[4] F. C. Grozema, C. Houarner-Rassin, P. Prins, L. D. A. Siebbeles, and H. L. Anderson, J. Am. Chem. Soc. 129 (2007) 13370.

[5] A. Pramanik, H. S. Kang, J. Chem. Phys. 134 (2011) 094702.

[6] A. Pramanik, H. S. Kang, J.Phys. Chem. A 115 (2011) 219.

Figures

Figure 1: Electric properties of a bilayer of armchair GNR with triplylinked (TL) and doubly-linked (DL) Zn-PPTs.

Figure 2: (Left) The geometrical structure of a ladder type doublestranded 1D system of Zn-PPT bridged by a BPY group. (Right) The change of the band gap as a function of the transverse electric field showing the giant Stark effect.

References

224

[1] H. S. Kang, Chem. Phys. 369 (2010) 66.

Figure 2: The geometrical structure of (CuCN)7 nanowire which includes 3 Li atoms per primitive cell, showing that Li atoms are located near C N group of three adjacent CuCN chains. For clarity, two primitive cells are shown along the c axis.

ď&#x201A;ş

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Invited Gate Control of the Electron Spin in Semiconductor Quantum Wells

UniversitĂŠ de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Avenue de Rangueil, 31077 Toulouse, France

Xavier Marie A. Balocchi P. Renucci T. Amand P. Renucci B.L. Liu and C. Fontaine marie@insa-toulouse.fr

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References

NANOSPAIN 2013

[1] A. Balocchi , Q. H. Duong, P. Renucci, B. L. Liu, C. Fontaine, T. Amand, D. Lagarde, X. Marie, Phys. Rev. Lett. 107, 136604 (2011) ; M.E. FlattĂŠ, Physics 4, 73 (2011).

[2] H. Q. Ye, G. Wang, B. L. Liu, Z. W. Shi, W. X. Wang, C. Fontaine, A. Balocchi, T. Amand, D. Lagarde, P. Renucci, X. Marie, Appl. Phys. Lett 101, 032104 (2012).

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The control of electron spin in semiconductors for potential use in transport devices or quantum information applications has attracted a great deal of attention in recent years. In nanostructures made of III-V or II-VI semiconductors, the absence of inversion symmetry and the spin-orbit coupling are responsible for the lifting of the degeneracy for spin up and down electrons states in the conduction band. This splitting plays a crucial role for the spin relaxation and spin transport properties. As it depends strongly on the crystal and nanostructure symmetry, it can be efficiently tailored as explained below.

We have measured the electron spin relaxation time in (111)-oriented GaAs quantum wells (QW) by time-resolved photoluminescence and timeresolved Kerr rotation spectroscopy. By embedding the QWs in a PIN or NIP structure we demonstrate the tuning of the conduction band spin splitting and hence the spin relaxation time with an applied external electric field applied along the growth direction [1].

The application of an external electric field of 50 kV/cm yields a two-order of magnitude increase of the spin relaxation time; this is a consequence of the electric field tuning of the spin-orbit conduction band splitting which can almost vanish when the Rashba term compensates exactly the Dresselhaus one [2].

Experiments performed under transverse magnetic fields demonstrate that in addition to the spin lifetime, the electron spin coherence time can be significantly increased.

The role of the Dresselhaus cubic terms on both the temperature dependence of the effect and the anisotropy of the spin relaxation will be discussed.

Finally the gate control of the electron spin diffusion length will be demonstrated.

Oral One dimensional Ordered Materials for Optical Applications: Pyronine Y dye into Aluminophosphates with different nanopore size

Virginia Martínez-Martínez 2 R. García 2 L. Gómez-Hortigüela J. Pérez-Pariente2, 1 R. Sola Llano and 1 I. López-Arbeloa

1

virginia.martinez@ehu.es 1

Departamento de Química Física, Universidad del País Vasco, UPV/EHU, Apartado 644, 48080, Bilbao, Spain.

2 Instituto de Catálisis y Petroleoquímica, ICP- CSIC. C/ Marie Curie 2. Madrid, Spain.

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The encapsulation of dyes into nanostructured ordered systems is a good strategy to provide new functional materials with interesting optical, chemical and electrical properties. In this regard, 1Dordered clays, zeolites and zeotypes microporous materials are very interesting host materials due to the open nature of their frameworks with well-defined internal channels.

These hybrid nanomaterials are characterized by a high organization degree where the photoactive molecule is aligned in a preferred position due to the geometrical restrictions imposed by the solid framework inducing highly monomeric and anisotropic dye distributions [1].

Generally, materials for optical applications require a high dye concentration. In those cases many dyes in adsorbed-state are aggregated [2].

Therefore, the incorporation of dye molecules in monomeric species is crucial, avoiding their tendency to self-associate since aggregates quench the fluorescence. In the cases, that aggregation cannot be totally suppressed, J- type aggregates (head-totail dyes), characterized by red-shifted emission respect to the monomers should be favored in detriment of H-aggregates (dyes in sandwich-like configuration) which are usually non-fluorescent and also quench the monomer emission.

The present work shows a computer-aided rational choice of 1D- magnesioaluminophosphate nanoporous hosts to occlude a xanthene-type dye, Pyronine Y (PY) in order to prepare highly fluorescent hybrid materials by preventing dye aggregation.

Thus, Pyronine Y (PY) dye is occlued into different unidirecctional aluminophosphates with different size pore (Figure): i) MgAPO-5 (AFI structure-type) with a 12-ring system of cylindrical channels with a diameter of 7.3 Å; ii) MgAPO-36 (ATS structure-

type), which possesses a 12-ring elliptical channel system with slightly smaller dimensions, 6.7 x 7.5 Å; iii) and MgAPO-11 (AEL structuretype) with a 10ring channel system of even smaller dimensions, 4 x 6.5 Å. Pyronine Y dye with a molecular size of (13.7 Å x 6.2 Å x 3.2 Å) will fit with its longer axis mainly aligned along the channel direction of the three materials under study.

PY/MgAPO-5 crystals show green emission under the optical fluorescence microscope (Fig. 1a) and high dichroic ratio values (Table) indicative of the encapsulation of PY molecules within the nanopores. The two life-times measured (Table) and the absence of new fluorescence bands for this sample confirms the co-existence of monomers and H-aggregates in this structure [3].

In contrast, formation of H-aggregates is suppressed by the encapsulation of PY within channels of smaller dimensions, such as those in PY/MgAPO-36 (ATS). The crystals of this sample show a multicolour emission under the optical fluorescence microscope from red (J-aggregates) to yellow (monomers and aggregates) to green (monomers). This system offers an antenna system that can harvest and transmit light in a wide range of the visible spectrum. DFT calculations show that only the channels in AFI are large enough to host the H-aggregates of PY. [4] Table. Main photophysical parameters of PY/MgAlPO; λexc: excitation maxima wavelength; λfl: fluorescence maxima wavelength; τfl: lifetimes Φfl: quantum yield; D: fluorescence dichroic ratio.

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References

[4] V. Martínez-Martínez, R. García, L. GómezHortigüela, J. Pérez-Pariente, I. López-Arbeloa (Submitted).

Figures

Figure 1: Fluorescence images of PY into the different MAPO structures (a), together with the view along the straight channels of the different structures (b).

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The channels of MgAPO-11 have the appropriate dimensions to completely suppress the formation of aggregated species. The intense green color and the measurement of an unique lifetime indicate that monomers are only present within the channels. The absolute quantum yield of the sample is similar to that recorded in diluted solution of PY, being more than one order of magnitude higher than those obtained for MgAlPO-5 or MgAlPO-36. Moreover, a huge anisotropic response to the linear polarized light is derived in this material with dichroic ratios ≥ 40.

DFT shows that the AEL nanochannels are optimal to prevent PY aggregation since, on the one hand, their small dimension avoid aggregates which involve stacking (H- and some J-aggregates), and on the other hand, their particular topology comprising side-pockets of size commensurate to that of PY impedes the dye to site close to each other in J-type coplanar configuration, hence forcing PY to arrange exclusively as monomers.

Our multi-approach work shows now how one can fine-tune the optical properties of host-guest materials by rationally selecting the appropriate framework with the aid of modeling tools [4].

In this work, we used a combination of synthesis work, advanced spectroscopic characterization and modeling tools in order to rationally select the most appropriate one-dimensional nanoporous aluminophosphate framework to incorporate the fluorescing dye Pyronine Y (PY) as monomers directly during the synthesis of the solids (crystallization inclusion). We report experimental evidences and modeling insights of how the “cage effect” of nanochannels, i.e. the pore size and their particular topology, can tune the optical properties of the hybrid composite material by controlling the aggregation state of the occluded dye. This study provides an essential contribution to the rational design and development of new optical materials.

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[1] P. Gómez-Romero, C. Sanchez in Functional Hybrid Materials, Wiley-VCH, Weinheim, Germany, 2004.

[2] M. Arik, Y. Onganer. Chem Phys Lett 375 (2003) 126-133.

[3] R. García, V. Martínez-Martínez, L. GómezHortigüela, I. López-Arbeloa, J. Pérez-Pariente.

Invited Nanotechnology in Electronic and Sensor Application

Meyya Meyyappan

m.meyyappan@nasa.gov NASA Ames Research Center Moffett Field, CA, USA

As a replacement for silicon CMOS at the end of scaling according to Mooreâ&#x20AC;&#x2122;s law, transistors based on carbon nanotubes and graphene have been explored by a number of groups across the world.

In contrast, we have developed nanoscale vacuum tubes or transistors. Vacuum tubes went away because they were bulky and consumed a lot of power while integrated circuit (IC) manufacturing allowed producing devices with ever-decreasing features sizes. However, vacuum is superior to any semiconductor in terms of electron transport due to absence of collisions. We have taken advantage of this and standard IC processing steps to construct nanoscale vacuum transistors. A plasma ashing step is critical to create the emittercollector gap to the desired level. Preliminary results for a gap of 150 nm show 0.4 THz performance and further scaling down can provide frequencies well into the THz regime.

We have also made progress on flexible electronics. Preliminary results on oxide nanowire based transistors and memory devices for etextile, and sensors fabricated on cellulose paper will be presented. Carbon nanotubes can be easily ink jet printed on paper to create gas/vapor as well as biosensors. Preliminary results from these efforts will be presented.

228

Acknowledgements: The author acknowledges JinWoo Han and Jessica Koehne.

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Invited Spin transition at the nanometer scale

LCC, CNRS & University of Toulouse, 31077 Toulouse, France

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gabor.molnar@lcc_toulouse.fr

can be preserved in nano-objects as small as 3 nm.

Furthermore, we have evidenced an important matrix effect on the particle properties, which allows one to tune the particle properties by modulating the particle/matrix interface or the matrix properties. Beyond the fundamental aspects, the elaboration of thin films and nanopatterns of spin crossover materials paves also the way towards very promising applications in nanophotonic and nano-electronic devices. The main interest of SCO complexes in this context is that they respond reversibly to various external stimuli and can be therefore used either to detect physicochemical changes in the environment (sensors) or, on the other way around, to control the device properties by an external stimulus (switching and memory devices).

[1] P. GĂźtlich, H. Goodwin (eds.), Top. Curr. Chem.

Vols. 233-235 (2004).

[2] A. Bousseksou, G. Molnar, L. Salmon, W. Nicolazzi, Chem. Soc. Rev. 40 (2011) 3313.

[3] H. J. Shepherd, et al. Eur. J. Inorg. Chem.

(2013) 1015.

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References

229

Spin crossover complexes of transition metal ions represent an important class of bistable materials for which switching between the high-spin and low-spin electronic configurations can be obtained by diverse external stimuli such as temperature, pressure, light irradiation, magnetic and electric fields or even the adsorption of gas/vapor molecules [1]. This switching of molecular spinstates is accompanied by a spectacular change of various physical properties. The molecular spin state change in the bulk material gives rise to elastic interactions between the molecules due to the strong electron-lattice coupling, leading to the emergence of various cooperative phenomena, such as first order phase transitions. These cooperative effects are considered as the key properties of these smart molecular systems for future applications in memory and highly efficient switching devices. The recent synthesis of these coordination compounds as nanoparticles, nanowires, thin films and nano-scale assemblies have brought new fundamental questions about the control and the preservation of the cooperativity at the nanometric scale [2-3]. In this presentation I will discuss the development of various top-down and bottom-up methods for the elaboration and patterning of nanometer scale thin films and particles of spin crossover complexes as well as our experimental results concerning size-reduction effects. While the first experimental studies were limited to large collections of nano-objects with a dispersion of sizes and shapes, we put particular emphasis for investigations in which SCO properties of the nanoobjects could be clearly correlated with their morphology (see figure). In the course of these investigations we have shown that the memory effect (hysteresis) inherent to the bulk material

GĂĄbor MolnĂĄr W. Nicolazzi L. Salmon and A. Bousseksou

Figures

230

Figure 1: Left panel: Scheme of a soft lithographic fabrication process for arrays of fluorescent spin crossover nanodots of the complex [Fe(hptrz)3](OTs)2. The AFM and fluorescence microscopy images of a nano-dot array are also shown with motifs of 370 nm lateral size, 3 Âľm pitch and a nominal depth of 150 nm. Right panel: Temperature dependence of the luminescence intensity of a single nanodot in the heating (red) and cooling (blue) modes [Quintero et al. J. Mater. Chem. 2012, 22, 3745].

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Oral High Throughput Electrospinning

Hipólito Montejano

hmontejano@bioinicia.com

Reference Development of zein-based heat-management structures for smart food packaging, Pérez-Masiá, R., López-Rubio, A., Lagarón, J.M. 2013 Food Hydrocolloids 30 (1), pp. 182-191.

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231

Electrospinning has emerged as a versatile method to produce submicron fiber mats from natural or synthetic polymers. However, it does still remain largely in a lab scale due to limited yielding from most commercial systems. Monoaxial and multiaxial structures, produced by concentric needles or other spinning devices, are of great interest in many applications and can also be made to generate high throughput systems. Fluidnatek® equipment and applications by Bioinicia S.L. aims at providing flexible electrospinning solutions from lab scale to pilot plant in various applications.

As an example, in the field of refrigeration, the encapsulation and incorporation of phase change materials (PCMs) inside refrigeration equipment can be commercialized as a plausible solution to buffer temperature variations along the whole cold chain. To this end, structures containing PCMs can be obtained by electrospinning which are subsequently compressed to form functional structures of interest in the application.

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Bioinicia S.L., Valencia, Spain.

Oral Exchange bias dependence in gradually patterned antiferromagnet 1

Rafael Morales

Dpto. de Química-Física, BCMaterials, Univ del País Vasco UPV/EHU, 48940 Leioa, Spain 2 IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain 3 Unité Mixte de Physique CNRS/Thales, Université Paris Sud, 91405 Orsay, France 4 Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla 92093 CA, USA 5 Dpto. de Química-Física, Universidad del País Vasco UPV/EHU, 48940 Leioa, Spain 6 Departament de Física Fonamental and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Catalonia, Spain

Exchange bias is a phenomenon associated with the exchange interaction at the antiferromagnetic/ ferromagnetic (AF/FM) interface. The exchange coupling between dissimilar materials shifts the center of the hysteresis loops along the external field axis by an amount known as exchange bias field (HEB). It is generally assumed that HEB decreases as FM thickness (tFM) increases following a dependence of 1/tFM [1]. In this work we investigate the dependence of FM layer thickness on the exchange bias field in continuous and patterned FeF2/FM (FM = Ni, FeNi) bilayers. The AF layer was gradually etched in patterned samples using a photolithography mask (Figure 1). tFM varies from 3 to 100 nm whilst the AF thickness under the FM layer was kept constant at 70 nm.

Experimental measurements reveal that HEB vs tFM largely deviates from the dependence of 1/tFM. A theoretical model considering spring-like domain walls through the FM layer [2,3] and a finite AF anisotropy [4] is taking into account to explain the results.

Work supported by MICINN and MINECO grants FIS2008-06249, MAT2010-20798, MAT2012-33037, European FEDER funds, European Community FP7PEOPLE-2012-IRSES-318901 and the US Department of Energy DE FG03-87ER-45332.

1,2

J.E. Villegas3 Ali C. Basaran4 D. Navas5 N. Soriano5 X. Batlle6 F. Castaño5 and Ivan K. Schuller4

rafael.morales@ehu.es

[4] M. Kiwi, J. Mejia-Lopez, R. D. Portugal, and R. Ramirez, Europhys. Lett., 48 (1999) 573.

Figures

Figure 1: A wedged FeF2/FM sample patterned into stripes.

References

232

[1] J. Nogués, Ivan K. Schuller, J. Magn. Magn.

Matter. 192 (1999) 203.

[2] R. Morales,Z-P. Li, O. Petracic, X. Batlle, and Ivan K. Schuller, Appl. Phys. Lett. 89 (2006) 072504.

[3] R. Morales,Z-P. Li, O. Petracic, X. Batlle, and Ivan K. Schuller, Appl. Phys. Lett. 89 (2006) 072504.

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Invited The road to publication in Nature Nanotechnology

Alberto Moscatelli

a.moscatelli@nature.com

Associate Editor, Nature Nanotechnology, Nature Publishing Group, 4, Crinan Street, N1 9XW, London, UK

Reference

Figures

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It comes a time you want to publish your results, and although good science will shine regardless of where the paper comes out, choosing the right journal is often critical. In this talk, I will try to explain how we, at Nature Nanotechnology, treat your manuscript after you granted us your trust and add value to your science. The choice of referees is the most important aspect of the peerreview process and we are especially careful in our selection. Like most Nature branded journals, we do not rely on an editorial board and are completely independent from Academic Societies.

The final decision on whether to publish or not is made by in-house, professional editors (it is 5 of us). With the help of sub-editors and art editors, we polish the text and work on the figures to make sure your science is accessible to the widest possible audience; the press-release team contacts main stream media if the topic is deemed of laymanâ&#x20AC;&#x2122;s interest. The upshot of this is that we can only concentrate on very few, selected manuscripts, forcing us to make difficult decisions.

Part of the talk will be devoted in trying to demystify the criteria we use to select the papers we publish.

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http://www.nature.com/nnano/index.html http://twitter.com/Naturenano

Oral Morphological and Structural Characterization of ZnO and TiO2 Nanoparticles

1

Sohel M S Murshed 2 V S Patil 2 K R Patil C A Nieto de Castro1 and 3 A Coronas

1

Centre for Molecular Sciences and Materials, Faculty of Sciences, University of Lisbon 1749-016 Lisbon, Portugal 2 Centre for Material Characterization, National Chemical Laboratory, Pune 411008, India 3 Department of Mechanical Engineering, Universitat Rovira i Virgili, 43007 Tarragona, Spain

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This work deals with the characterization study of structural and morphological features of Zinc oxide and Titanium dioxide nanoparticles to better understand their role in anomalous properties of nanofluids and ionanofluids. These nanoparticles were purchased from IoLiTec (Ionic Liquids Technologies, Germany) and they have numerous potential applications such as in electrodes for solar cells, photocatalytic decontamination, piezoelectrics, pigments for paints, photochemical degradation, catalysts and catalyst supports, and UV protection. In addition, these nanoparticles laden nanofluids and ionanofluids can be used for advanced heat transfer and green energy-based applications [1-4]. Both the nanofluids and ionanofluids are new classes of fluids which are prepared by dispersing nanoparticles in conventional thermal fluids and ionic liquids, respectively [1, 3-4]. Using these nanoparticles we aim to prepare ionanofluids and to investigate their various properties. However, prior to studying any properties or applications of nanofluids or ionanofluids, it is crucial to have clear information about morphology and structures of the nanoparticles to be dispersed.

The morphology and size of nanoparticles was studied by using a high resolution transmission electron microscopy (TEM) (FEI Technai F30) at an acceleration voltage of 300 kV. In order for TEM study, very dilute suspensions of nanoparticles in ethanol was prepared before placing and drying out the sample on carbon coated copper grid. The TEM images in Fig.1 show the morphology and structure of nanoparticles. It can be seen that while TiO2 nanoparticles are not fully spherical, ZnO are of spherical shape. The average sizes of ZnO and TiO2 nanoparticles were found to be about 15-20 nm and 35-45 nm, respectively and

smmurshed@fc.ul.pt

they are very close to the initial sizes of these nanoparticles provided by the company. Although nanoparticles are found to be of uniform sizes, they form aggregation which can play important role in changing the properties of their suspensions in fluids.

In order to identify the crystal structures and defects of nanoparticles, the selected area electron diffraction (SAED) technique was used.

The SAED patterns of both nanoparticles are shown in Fig.2 which indicates the presence of mono-crystallite particles.

The X-ray diffraction (XRD) analysis of these nanoparticles was also performed by using a computer controlled XRD system of PAN Analytical Powder XRD instrument at an operating rate of 40 KV and 30 mA (Cu-Kα radiation λ=0.1548 nm) in the 2Ѳ range of 10-80 degrees. The PCPDFWINXRD software was used for matching with the standard JCPDS cards. By comparison with the data from JCPDS cards (e.g., #86-0148 for TiO2) the diffraction patterns of these nanoparticles can be indexed to the hexagonal phase. Fig.3 presents the XRD patterns of both nanoparticles. The XRD patterns in Fig. 3(b) showed several strong diffraction peaks which confirm the rutile phase of TiO2. Nevertheless, the diffraction peaks in both patterns indicate good crystallinity of nanoparticles and almost no peaks of impurity were observed confirming the high purity of these nanoparticles. A detailed analysis of the findings of this study will provide better understanding of the role of structural and morphological features of nanoparticles in the anomalous thermophysical and other properties of these new fluids.

Acknowledgements: This work was supported by International Research Staff Exchange Scheme of

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Marie Curie Actions (European FP7)-New Working Fluids based on Natural Refrigerant and Ionic Liquids for Absorption, Refrigeration–NARILAR and

by FCT-Portugal to CCMM, FCUL.

References [1] Murshed S.M.S., Leong K.C. and Yang C., Thermophysical and electrokinetic properties of nanofluids- A critical review, Applied Thermal Engineering 28 (2008) 2109-2125.

[2] Murshed S.M.S., Nieto de Castro C.A., Lourenço M.J.V., Lopes M.L.M. and Santos F.J.V., A review of boiling and convective heat transfer with nanofluids, Renewable and Sustainable Energy Reviews 15 (2011) 23422354.

[3] Murshed S.M.S. and Nieto de Castro C.A., Nanofluids as advanced coolants, in Green Solvents I: Properties and Applications in Chemistry, Eds., Mohammad A. and Inamuddin, Chapter 14 (2012) 397-415, Springer, London.

[4] Murshed S.M.S., Nieto de Castro C.A., Lourenço M.J.V., Lopes M.L.M. and Santos F.J.V., Current research and future applications of nano- and ionano-fluids, Journal of Physics Conference Series, 395 (2012) 012117 (8pp).

Figure 2: SAED patterns of (a) ZnO and (b) TiO2 nanoparticles.

Figure 3: XRD patterns of (a) ZnO and (b) TiO2 nanoparticles.

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Figures

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235

Figure 1: TEM images of (a) ZnO and (b) TiO2 nanoparticles.

Oral Preparation of Copper Nitride Nanoparticles in Long-chain Alcohol and Its Thermal Decomposition Property

Takashi Nakamura T. Ebina, H. Hayashi and T. Hanaoka

nakamura-mw@aist.go.jp

Research Center for Compact Chemical System, National Institute of Advanced Industrial Science and Technology.

4-2-1 Nigatake, Miyaginoku, Sendai, 983-8551, Japan.

236

We are attending copper nitride (Cu3N) as a precursor of conducting material for printed electronics device. In this presentation, we demonstrate that Cu3N particles were prepared in a long-chain alcohol with ammonia gas bubbling and characterized by XRD and TEM. Additionally, thermally decompose property of prepared and purchased Cu3N were compared by TG-DTA measurement.

Introduction Metal nitride has chemical and physical properties which metal oxide is unable to achieve. As the characteristic properties of metal nitride, semiconducting and magnetic properties are included [1] Gallium nitride is well known as a material for blue LED. For a hard magnetic material, Ion nitride is a candidate of replacing material from rare earth metal such as neodymium and samarium. [2] Copper nitride has not been used as oxidation-resistant of copper but also researched as a candidate of a recording material or a catalyst. As new application of copper nitride, we have focused on an electrical conducting material for printed electronics device because of its oxidation resistant property and thermal decomposition property which copper nitride decompose into copper and nitrogen at approximately 300 °C as bulk state. [3] Additionally, by combination with nano-sized effect such as decreasing melting point, it is able to decrease decomposition temperature of the copper nitride. Therefore, an electro conducting ink having oxidation-resistant and sintering around 200 °C will be developed. Nano-sized copper nitride was prepared by solvothermal or high temperature condition over 250 °C, previously.

Choi et al. [4] reported that copper nitride prepared from CuCl2 and NaN3 as reagents in

toluene or THF as solvents in an autoclave. Wu et al. [5] and Wang et al. [6] reported that mono dispersed nano Cu3N particles were prepared from Cu(NO3)2 in octadecylamine by heating at 280 °C. In this presentation, we present new preparation method of nano-sized copper nitride without pressurized or high-temperature condition. Copper nitride was prepared in an alcohol solvent with ammonia bubbling at 190 °C heating. Obtained Cu3N powder was characterized by XRD and TEM. Moreover, thermal decomposition property was compared between prepared and purchased copper nitride by TG-DTA measurement.

Experimental Copper (II) acetate (400 mg) was dispersed in 1nonanol (100 mL) in a three-neck flask. The solution was heated with ammonia bubbling at 190 °C by using an oil bath. At the time of heating, the color of solution changed from clear deep-blue to opacity red-brown. Red-brown powder was obtained by centrifugation of the heated solution.

The obtained powder was characterized by XRD and TEM. Thermal decomposition property of the powder was measured by TG-DTA. Results Crystal structure of the obtained powder was determined by XRD measurement (fig. 1). From observed peaks at 23.40, 33.34, 41.12, 47.84, 53.92, and 59.55° attributed (100), (110), (111), (200), (210), and (211), respectively, the crystal structure was determined Cu3N having anti-ReO3 structure (JCPDS No. 47-1088). No peaks deriving from Cu and CuO were observed. Morphology and size of Cu3N powder was observed by using a TEM (fig. 2). Obtained Cu3N powder has shape of granular particle with less than 200 nm of diameter consisted by angular Cu3N nano crystalline with less than 20 nm on a side. These

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small particles distributed in an observing view of TEM. Thermal decomposition properties of Cu3N nanoparticles and purchased Cu3N (Santa Cruz Biotechnology, Inc.) under argon atmosphere were compared by TG-DTA (fig. 3). For the prepared Cu3N, weight lost until at 221 °C. Over the temperature, the weight of sample increased after an exothermic peak with a peak top at 221 °C. For purchased Cu3N, the weight lost until 439 °C. Over the temperature, the weight of the sample increased with an exothermic peak with a peak top at 439 °C. From these comparisons, decomposition temperature of prepared Cu3N decreased over 200 °C compared with purchased one. Crystal structure of powder heated by TG-DTA at 400 °C under argon atmosphere was characterized by XRD. Heated powder gave a diffraction pattern of CuO. Nevertheless powder was heated under argon atmosphere, no diffraction pattern Cu give from Cu3N. This time, we cannot trace decomposition of Cu3N to Cu and N2 which was published literatures previously. [3] Summary Cu3N nanoparticles having less than 200 nm of second particle diameter consisted first particle diameter having less than 20 nm on a side were prepared from copper acetate and ammonia as reagents in a long-chain alcohol as a solvent.

Decomposition temperature of the prepared Cu3N was decreased over 200 °C comparing with purchased Cu3N.

Figures

Figure 1: XRD pattern of obtained sample.

Figure 2: TEM image of obtained sample.

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Figure 3: TG-DTA curves of prepared (red) and purchased Cu3N (black).

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[1] C. Giordano, M Antonietti, Nano Today, 6 (2011) 366.

[2] J. M. D. Coey, P. A. I. Smith, J. Magn. Magn.

Mater., 200 (1999) 405.

[3] M. Asano, K. Umeda, A. Tasaki, Jpn. J. Appl.

Phys., 29 (1990) 1985.

[4] J. Choi, E. G. Gillan, Inorg. Chem., 44 (2005) 7385.

[5] H. Wu, W. Chen, J. Am. Chem. Soc., 133 (2011) 15236.

[6] D. Wang, Y. Li, Chem. Commun., 47 (2011) 3604.

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References

Oral The ratio protein-silver modulates the availability of ionic silver and the potential toxicity of silver nanoparticles: applications for cheaper and more effective consumer products 1 2 3

1

enrique.navarro@ipe.csic.es

Pyrenean Institute of Ecology-CSIC, Av. MontaĂąana 1005, Zaragoza 50059, Spain Eawag, Ă&#x153;berlandstrasse 133, DĂźbendorf 8600, Switzerland University Analytical Research Group, I+D+i Building, C/Mariano Esquilor s/n, Zaragoza 50018 Spain

Because of their biocide properties [1], silver nanoparticles (AgNP) are present in numerous consumer products. During recent years, an increasing number of works demonstrated their toxicity to different microorganisms as bacteria [14] or algae [5-8]. Biocide properties of AgNP have been suggested to relate with both the release of ionic silver (Ag+) and interactions between AgNP and cell membranes [2, 7, 9-11]. The determinant role of dissolved silver ions, in explaining the observed toxicity of AgNP to microorganisms, has been experimentally evidenced by evidenced by the fact that complexation of Ag+ ions by thiol ligands as well as anaerobic conditions prevent toxicity of AgNP [12-15]. These results emphasize the importance for disentangling the contribution of AgNP and Ag+ to the observed toxicity.

There are only a few works available, focusing on the influence of coatings on ionic silver release from AgNP [17-19].These studies emphasize their role in complexing and storing silver ions suggesting a potential control of silver bioavailability by the coatings.

However, desorption and release of ionic silver will ultimately depend on the affinity of membrane transporters to Ag+. Although some comparative studies with various coatings have indeed reported on differences in AgNP toxicity to aquatic organisms [7, 20, 21] none have systematically examined how coatings influence Ag+ bioavailability to organisms.

In this study we have assessed the toxicity of nanoparticles presenting different % of casein and silver.

These thee products presented 72,5% total Ag, 21,03% and 7,88% of total Ag. Toxicity was measured as the impact of the different compounds on the photosynthetic yield of

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Enrique Navarro 1 P. Salas 2 N. Odzak and Y. Echegoyen2

Chlamydomonas rehinadrtii. The amount of ionic silver toxically active was assessed using ultrafiltration and ICP-MS and also by Diffusive Gradients in Thin-films. Cysteine, a strong silver ligand, prevented in all cases the toxicity of silver nanomaterials, demonstrating the key role of ionic silver on the toxicity. Therefore, Effective Concentrations (EC50) were calculated as a function of the ionic silver measured.

Results, expressed as a function of measured ionic silver, shown that the product containing 21% of silver was 10 times more effective (EC50 is ten times smaller) than the nanomaterial presenting 70% of silver. Even if coatings are commonly used to mininimize nanoparticle aggregation in liquids [13, 16], these results shown that coatings may also optimize the delivery of ionic silver from nanomaterials. The final result would be a more effective and cheap consumer product.

References [1] Panacek, A., et al., Silver colloid nanoparticles: Synthesis, characterization, and their antibacterial activity. Journal of Physical Chemistry B, 2006. 110(33): p. 16248-16253.

[2] Pal, S., Y.K. Tak, and J.M. Song, Does the antibacterial activity of silver nanoparticles depend on the shape of the nanoparticle? A study of the gram-negative bacterium Escherichia coli. Applied and Environmental Microbiology, 2007. 73(6): p. 1712-1720.

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Environmental Contamination and Toxicology, 2008. 55(1): p. 70-7.

[14] Xiu, Z.M., J. Ma, and P.J.J. Alvarez, Differential Effect of Common Ligands and Molecular Oxygen on Antimicrobial Activity of Silver Nanoparticles versus Silver Ions.

Environmental Science & Technology, 2011.

45(20): p. 9003-9008.

[15] Udovic, M. and D. Lestan, Eisenia fetida avoidance behavior as a tool for assessing the efficiency of remediation of Pb, Zn and Cd polluted soil. Environmental Pollution, 2010.

158(8): p. 2766-72.

[16] Neubauer, S.C., D. Emerson, and J.P. Megonigal, Microbial oxidation and reduction of iron in the root zone and influences on metal mobility, in Biophysico-chemical processes of heavy metals and metalloids in soil environments, A. Violante, P.M. Huang, and G.M. Gadd, Editors. 2008, John Wiley & Sons: New York. p. 339-371.

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[3] Lee, W.F. and Y.C. Huang, Swelling and antibacterial properties for the superabsorbent hydrogels containing silver nanoparticles. Journal of Applied Polymer Science, 2007. 106(3): p. 1992-1999.

[4] Shahverdi, A.R., et al., Synthesis and effect of silver nanoparticles on the antibacterial activity of different antibiotics against Staphylococcus aureus and Escherichia coli.

Nanomedicine-Nanotechnology Biology and Medicine, 2007. 3(2): p. 168-171.

[5] Warheit, D.B., et al., Development of a base set of toxicity tests using ultrafine TiO2 particles as a component of nanoparticle risk management. Toxicology Letters, 2007.

171(3): p. 99-110.

[6] Hund-Rinke, K. and M. Simon, Ecotoxic effect of photocatalytic active nanoparticles TiO2 on algae and daphnids. Environmental Science and Pollution Research, 2006. 13(4): p. 225232.

[7] Spurgeon, D.J., et al., Responses of earthworms (Lumbricus rubellus) to copper and cadmium as determined by measurement of juvenile traits in a specifically designed test system. Ecotoxicology and Environmental Safety, 2004. 57(1): p. 54-64.

[8] Navarro, E., et al., Environmental behavior and ecotoxicity of engineered nanoparticles to algae, plants, and fungi. Ecotoxicology, 2008.

17(5): p. 372-386.

[9] Pinto, E., et al., Heavy metal-induced oxidative stress in algae. Journal of Phycology, 2003. 39: p. 1008-1018.

[10] Morones, J.R., et al., The bactericidal effect of silver nanoparticles. Nanotechnology, 2005.

16(10): p. 2346-2353.

[11] Sondi, I. and B. Salopek-Sondi, Silver nanoparticles as antimicrobial agent: a case study on E-coli as a model for Gram-negative bacteria. Journal of Colloid and Interface Science, 2004. 275(1): p. 177-182.

[12] Udovic, M. and D. Lestan, The effect of earthworms on the fractionation and bioavailability of heavy metals before and after soil remediation. Environmental Pollution, 2007. 148(2): p. 663-8.

[13] Li, L.Z., et al., Effect of major cations and pH on the acute toxicity of cadmium to the earthworm Eisenia fetida: implications for the biotic ligand model approach. Archives of

Oral Innovative Patterning Strategies and Process Control using MultiApplication Nanolithography Tools for Microfiltration, Solar Cells and Bragg Gratings

Frank Nouvertné 1 M. Kahl 1 A. Rudzinski M. Fleger2 and 2 O. Humbach

1

nouvertne@raith.de

1

RAITH GmbH, Konrad-Adenauer-Allee 8, Dortmund, 44263, Germany temicon GmbH, Konrad-Adenauer-Allee 11, Dortmund, 44263, Germany

2

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With a growing world population, nanotechnology can be one approach to address the rising demands for improving quality of food, green energy, communication and security.

For e.g. milk production [1], nanosieves are proposed to serve a growing need for microfiltration in order to increase shelf life and preserve the sensory quality of the product [2-4].

Solar cells are seen as a promising method for energy generation, but their cost and efficiencies would need to be drastically improved in order for them to become a viable option. E.g. adding photonic crystal arrays can potentially enhance the efficiency of these devices [5-6].

High quality Bragg gratings are indispensable ingredients of modern communication and optical variable devices, and are used for filters and multiplexers or security labels respectively. Subnm pitch control and perfect periodicity of such gratings over large areas is still a challenge.

The corresponding nm-sized patterns of above applications consist of large circle or line arrays, which can cover several cm2. Writing times with conventional electron beam lithography (EBL), stitching errors, and pitch control are crucial issues, which can significantly affect device performances.

We present the differences between two EBL patterning modes, one being the conventional stitching EBL, and the other a new and unique “stitch-error-free” EBL writing strategy called MBMS - a Modulated Beam and Moving Stage lithography module that comprises the design, control, and patterning of periodic nanostructures over large areas. In the MBMS exposure mode, the beam movement is defined such that the combination of repetitive beam patterning and synchronized continuous movement of the

laserinterferometer stage results in stitch-free strips of periodic nanostructures. We demonstrate that this technique can produce large circle arrays for nanosieves, photonic crystals with uniform pore size distributions and highest quality Bragg gratings - with fast patterning times, high pitch accuracy and virtually no stitching boundaries.

References [1] http://www.microfiltration.nl/index.php.

[2] Rijn, C. J. M.; Elwenspoek, M. IEEE Conf.

MEMS’95, 1995; pp 83-87.

[3] Mulder, M., Basic Principles of Membrane Technology; Kluwer, Academic Publishers: Norwell, MA, 1998.

[4] Freitas, R. A. Stud. Health Techn. Infor. 2002, 80, 45-59.

[5] Munday, Jeremy, N., Journal of Applied Physics, 112, 6, (2012).

[6] Jeong, S., Wang, S., Cui, Y., J. Vac. Sci. Technol., A30(6), (Nov/Dec 2012).

Figures

Figure 1: Exposure methodology of Modulated Beam and Moving Stage technology.

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Figure 2: A micro filter featuring a 3mm x 3mm area circle array in a nickel membrane.

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Figure 3: Hexagonal array of a 1mm-long, stiching error free photonic crystal waveguide written with MBMS stage technology.

Oral Bottom-up approach to epitaxial complex oxide nanostructures and nanocomposite thin films with outstanding magnetic, superconducting and electronic properties

Institut de Ciència de Materials de Barcelona-CSIC, Campus UAB, 08193 Bellaterra, Catalonia, Spain

242

Generation of large area arrays of self-organized oxide nanostructures (nanodots, nanowires) and thin films or nanocomposites provides unique opportunities for the development of novel functionalities with a wide range of potential applications (magnetic, superconducting, electronic, etc.). Bottom-up approach allows the fabrication of complex oxide nanostructures by self-organization, where spontaneously ordered, large-area patterns of nanometric objects appear.

In this context, and although much less studied, chemical solution deposition (CSD) offers a high throughput and cost-efficient route for the generation of complex oxides. This bottom-up approach to thin films can be additionally combined with other thin film growth approaches such as ALD. In recent years we have widely investigated the unique microstructural and physical properties of different sorts of CSD and ALD grown functional oxide nanostructures and thin films, including CeO2, ferromagnetic La1-xSrxMnO3 (LSMO) and YBa2Cu3O7 (YBCO) - derived nanocomposite superconductors [1-13]. Here I will review a few outstanding properties of these complex oxides where interfacial and internal strain is controlled at the nanoscale.

I will show first how the choice of the substrate and the interfacial strain anisotropy can be used to determine the shape and dimension of selfassembled CeO2 oxide nanostructures which are used as model systems. Understanding the nucleation and growth mechanisms of these epitaxial nanostructures has become possible through kinetic and thermodynamic analysis carried out with the support of tools such as RTA furnaces. The CSD approach has been used as well to obtain ultrathin films, self-assembled islands

Xavier Obradors, T. Puig, N. Mestres, A. Palau, M. Coll, S. Ricart, J. Gázquez, J. Arbiol, C. Ocal, A. Queraltó, M. Gibert, J. Zabaleta, A. Llordés, C. Moreno, A. Carretero, V. Rouco, R. Guzmán, M. de la Mata, J.C. González and P. Cayado

xavier.obradors@icmab.es

and nanowires of ferromagnetic La1-xSrxMnO3. We show first that metal-insulating transitions may be induced through strain control in ultrathin films, second we show by MFM and PEEM that the size and shape of islands control the ferromagnetic domain structure (single, multiple domain and vortex). On the other hand, we will also demonstrate that novel nanostructures and nanomaterials, such as a monoclinic high Tc ferromagnet, can be stabilized when polymeric templates are used to generate the oxide nanostructures.

Nanoscale manipulation of the electronic and physical properties of complex oxides can be achieved through the use of Conductive-Scanning Force Microscopy. We will show, for instance, that the electronic properties of LSMO and YBCO thin films can be drastically modified through reversible resistive switching transitions. The potential of this tool to design novel devices will be discussed.

I will finally report on the remarkable performance of CSD epitaxial superconducting YBa2Cu3O7 nanostructured films with second phase insulating nanoparticles where the nanostrain induced at the interfaces, as quantified by HRSTEM-EELS, controls the local superconducting properties. These novel complex oxide materials have allowed to demonstrate that a complex vortex pinning landscape can be engineered in these high current superconducting materials and also that strain leads to local suppression of Cooper pair formation, accordingly with the predictions of the Bond Contraction Pairing model.

This extensive overview of recent work on complex oxide nanostructured functional materials will serve to stress the high potential of the bottom-up approaches based on chemical solutions to create novel materials with outstanding performances.

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References

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[1] M. Gibert et al.; Adv. Mater. 19 (2007) 3937.

[2] C. Moreno et al.; Adv. Funct. Mater. 19 (2009) 2139.

[3] M. Gibert et al.; Small 23 (2010) 2716.

[4] A. Carretero-Genevrier et al.; J. Am. Chem Soc. 133 (2011) 4053.

[5] P. Abellán et al.; Appl. Phys. Lett. 98 (2011) 041903.

[6] J. Zabaleta et al. ; J. Appl. Phys. 111 (2012) 024307.

[7] C. Moreno et al. ; Nano Lett. 10 (2010) 3828.

[8] J. Gutierrez et al. ; Nature Mater 6 (2007) 367.

[9] A. Llordés et al. ; Nature Mater 11 (2012) 329.

[10] A. Carretero-Genevrier et al.; Chem. Comm. 48 (2012) 6223.

[11] M. Coll et al.; Chem. of Mater. 24 (2012) 3732.

[12] J. Zabaleta et al. : Nanoscale (2013).

[13] R. Guzmán et al. ; Appl. Phys. Lett. (2013).

Oral 1

Interaction of ammonia vapors with CdSe/ZnS quantum dots in porous matrices

1

Anna O. Orlova 1 Y. A. Gromova , 1 V.G. Maslov A.V. Baranov1 1 A.V. Fedorov and 2 M.V. Artemyev

National Research University of Informational Technologies, Mechanics and Optics, 197101 St. Petersburg, Russia 2 Institute for Physico-Chemical Problems, Belarusian State University, 220080 Minsk, Belarus

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Ammonia is a one of the most wide spread compounds in the nature and industry. At the same time ammonia vapor can be harmful for human health [1]. Therefore, monitoring and detection of the ammonia vapor are very actual and important problem. One way of detection of different compounds is the use of specific molecules or particles that can change their properties due to interaction with the analyte. In particular, using of optical technologies enable ones to detect of ammonia with high sensitivity [2].

Nowadays a colloidal synthesis of a new class of inorganic luminophore, semiconductor quantum dots (QDs), is well developed [3]. QDs possess some helpful properties, the most important of them is size-dependence of QD optical characteristics (absorption and luminescence). This property along with a high extinction, a high quantum yield of luminescence, a high photo- and chemical stability allows them to compete with conventional luminophores. Combining the features of the semiconductor QDs with specific porous matrices that can concentrate analyte species allows getting a new class of luminescent sensor system with the high sensitivity and a broad dynamic range.

Here we discuss two types of porous matrices impregnated with CdSe/ZnS quantum dots, which can change their luminescent properties due to interaction with ammonia vapor. In present study bright luminescent hydrophobic CdSe/ZnS quantum dots were embedded in terephthalate track pore membranes (TM) with pore size of 500 nm and in a borosilicate porous glass (BG) with pore size of 17 nm. The systems are shown in Figure 1. The CdSe/ZnS quantum dots embedded in the TM are quasi-isolated and possess optical properties like those in QD colloidal solution [4].

a.o.orlova@gmail.com

For QDs embedded in the porous glass, the steadystate absorption and luminescence spectra also coincided with those in colloidal solution, however an average luminescence decay time became one and a half times longer, 20 ± 2 ns vs 32 ± 2 ns. We propose that the adsorption of quantum dots on the inner surface of pores decreases a number of QD surface defects responsible for nonradiative deactivation of the QD excited states. This results in an increase in the luminescent average decay time of QDs. The optical properties of QDs embedded in the porous glass indicates that in this matrix QDs are isolated and do not interact with each other.

In order to investigate an interaction of the ammonia vapors with our samples we have incubated them in a hermetic box of 16 ml volume with 5 μl drop of 10% ammonia water solution on its bottom. Since samples did not contact with the drop of the ammonia solution the QDs interacted only with ammonia vapors with concentration of ~1.7∙10-3 mol/l. We have observed that in both matrices the interaction of ammonia vapors with QDs leads to significant quenching of their luminescence and shortening their luminescent decay time (see Figure 2). We propose that in both matrices ammonia molecule form a complex with QD via coordination onto surface Zn ion of the QD shell similar to the QD/pyridine complexes [5].

Figure 2 shows that the luminescence response of QDs exposed to ammonia vapors differs for the TM and the BG samples. The dependence of QD luminescence decay on the time of interaction with ammonia vapors clearly shows that an adsorption of one ammonia molecule onto QD surface does not lead to complete quenching of this QD. It means that the degree of luminescence quenching of QD depends on stoichiometry of the QD/ammonia complex, i.e. on the number of

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References [1] R.C. Barth, P.D. George, R.H. Hill. EH&S for hazardous waste sites, Fairfax, Va.: American Industrial Hygiene Association, 2002.

[2] H.S. Mader and O.S. Wolfbeis. Anal. Chem.

82(2010) 5002.

[3] D.V. Talapin et al. Nano Letters. 1(2001) 207.

[4] A.O. Orlova et al. Nanotechnology 22 (2011) 455201.

[5] X. Ji et al. JACS 130(2008) 5726.

[6] A. Aharoni et al. Phys.Rev. Lett. 100(2008) 057404.

[7] Ă&#x2030;. I. Zenâ&#x20AC;&#x2122;kevich et al. Theor. Exp. Chem.

1(2009) 23.

Figures

Figure 2: Dependencies of luminescence intensity (1) and decay time (2) of the CdSe/ZnS QDs embedded in the porous matrices: a) The terephthalate track pore membrane. b) The borosilicate porous glass.

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Figure 1: (a) QDs in the terephthalate track pore membrane, sketch and the 3D confocal luminescent image. (b) QDs in the borosilicate porous glass, sketch and the photos.

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ammonia molecules per QD. We assume that passivation of QDs in the BG matrix leads to a significant decrease a number of Zn ions on QD surface that can serve as coordination centers for ammonia. Therefore, this can lead to a decrease of the degree of luminescent quenching of QDs as compared with the TM matrix.

It should be noted that formation of QD/molecules complexes is often accompanied with an appearance of new nonradiative channels of deactivation of excited state of QDs, which compete with the energy or charge transfer in these complexes. Usually a nature of these channels is not clear. In the complexes of CdSe/ZnS QDs with ammonia molecule the energy or charge transfers are excluded. So, an effective quenching of QD luminescence in these complexes should be explaining by other reasons. A mechanism of the luminescence quenching and the reduction of QDs decay time is not quite clear at the moment. We believe that in the complexes of CdSe/ZnS QDs with ammonia molecule the reasons of luminescence quenching of QDs could be an energy transfer from QD to NH-vibration of ammonia molecule [6] or an appearance of new local sites on the QD surface at the points of coordination of molecules [7], which can serve as electron traps. Additional studies are now in progress.

The reusability is a one of important characteristics of any sensor elements. In our samples we found that full recovering the luminescent properties of QDs exposed to ammonia vapors took place after 10 min vacuum degassing at ~1 torr pressure. After complete cycle of adsorption/desorption of the ammonia molecules on the surface of CdSe/ZnS QDs embedded in the matrices we have examined the ability of QDs to adsorb a new portion of ammonia molecules. Repeated forming the QD/ammonia complexes under the same conditions showed that QDs keep their photophysical properties after interaction with the ammonia molecules. Therefore, this system could be used as reusable sensor on the ammonia vapors.

The dependence of luminescent properties of QDs on number of ammonia molecules adsorbed on their surface opens up the possibility to use the CdSe/ZnS quantum dots embedded in the porous matrices as a sensor element for quantitative detection of the ammonia vapors.

Oral 1

Poly(lactic acid)-modified carbon nanotubes for poly(lactic acid) composites

Maria C. Paiva 1 J. A. Covas 1 R. M. Novais F. Simon2 2 P. Pötschke and 2 T. Villmow

1

mcpaiva@dep.uminho.pt

Institute for Polymers and Composites/I3N, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal 2 Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, D-01069 Dresden, Germany

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Acknowledgements: The authors acknowledge the financial support from the Portuguese Foundation for Science and Technology through project POCI/QUI/59835/2004 and PhD grant SFRH/BD/32189/2006.

References [1] Paiva, M. C.; Simon, F.; Novais, R.; Ferreira, T.; Proença, M.; Xu, W.; Besenbacher, F, ASC Nano, 4 (2010) 7379.

Figures 100

CNT250

90 85

CNT250-PLA PLA

80

Derivative Weight (%)

2.5 CNT

95

Weight (%)

The present work reports the study of the effect of chemical functionalization of carbon nanotubes (CNT) on their dispersion in poly(lactic acid). The nanotubes were functionalized by the 1,3-dipolar cycloaddition reaction, generating pyrrolidine groups at the nanotube surface [1]. Further reaction of the pyrrolidine groups with poly(lactic acid) was studied in solution and in the polymer melt. The former involved refluxing the nanotubes in a dimethylformamide solution of the polymer, the latter was carried out by direct melt mixing in a microcompounder. The CNT collected after each process were characterized by thermogravimetry (TGA) and by X-ray photoelectron spectroscopy (XPS), showing evidence of polymer bonded to the nanotube surface only when the reaction was carried out in the polymer melt. Figure 1 presents the TGA curves obtained for the CNT as-received, functionalized under different conditions (CNT2510, CNT250) and further functionalized with the polymer (CNT250-PLA). The composites with polymer modified nanotubes presented smaller average agglomerate area and a narrower agglomerate area distribution. In addition, they showed improved tensile properties at low CNT concentration and presented lower electrical resistivity. Figure 2 presents the agglomerate area distribution for composites with 2 wt.% CNT with different functionalization, as well as the electrical resistivity measured for composites with different CNT contents.

PLA

2 1.5 CNT250-PLA

CNT 210

1 CNT250

0.5

CNT

CNT210

75

0 100

300

500

Temperature (ºC)

700

100

300 500 Temperature (ºC)

700

Figure 1: TGA curves of as-received CNT, functionalized CNT and PLA.

Figure 2: a) Electrical resistivity for PLA composites with nonfunctionalized and functionalized CNTs and b) cumulative area ratio for 2.0 wt% composites. The insert optical micrographs illustrate the observed agglomerate dispersion.

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Invited Magneto-transport in large area epitaxial graphene grown on SiC: 1 2 3

CNRS - Laboratoire de Photonique et de Nanostructures, 91460 Marcoussis, France Laboratoire National de Metrologie et d'Essais, 78197 Trappes, France Laboratoire des Physique de Solides, F-91505, Orsay, France

1

Emiliano Pallecchi 1 1 M. Ridene , D. Kazazis 2 2 F. Schopfer , W. Poirier M. Goerbig3, D. Mailly1 1 and A. Ouerghi

emiliano.pallecchi@lpn.cnrs.fr

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In this talk I will present magneto-transport measurements on epitaxial graphene grown on SiC(0001), either under UHV or atmospheric pressure. A low pressure growth results in lowmobility devices were both a localized state at low magnetic fields and a quantum Hall state at higher fields are observed. We find that for sufficiently strong disorder the system undergoes a direct transition from an insulating to a relativistic Hall conductor regime. Analysis of the magnetoconductivity hints to a quantum phase transitions, rather than a simple crossover. For samples grown at atmospheric pressure we find high mobilities, up to 10.000 cm2/Vs, and we observe quantum Hall plateaus around filling factors n=2,6,10,14.

Given the large sizes of our graphene Hall bars, the quantum Hall breakdown current are large, which is promising for metrological applications. Finally, I will briefly discuss the case of multi-layer graphene grown on SiC(000-1).

Oral Optimization of glass nanofibers productivity in Laser Spinning process

Joaquin Penide Felix Quintero O. Dieste A. Riveiro R. Comesaﾃｱa F. Lusquiﾃｱos and J. Pou

Dpto. Fﾃｭsica Aplicada, Universidad de Vigo, E.E. Industriais, 36310 窶天igo, Spain fquintero@uvigo.es

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Nanometric structures have attained an enormous importance over the last two decades because of its singular and interesting properties. The quasione dimensional structures such as nanofibers or nanowires are one of the most prominent among nanomaterials.

Laser Spinning has demonstrated the capability to obtain very long amorphous ceramic nanofibers. It mainly consists in melting a small volume of material (precursor drop) by a laser beam while stretching it by means of an assist gas applied at high speeds (supersonics). Then, this assist gas rapidly chills the melted material so it solidifies in a vitreous fiber. The production of nanofibers from different materials was previously reported [1-4].

There are several factors affecting this process, but viscosity is a key factor in the process determining whether the formation of a nanofiber succeeds or not. The viscosity of the molten volume must remain in a certain range in order to allow the elongation and keep stability; therefore its temperature must be restrained to produce fibers.

More specifically, the surface tension to viscosity ratio of the melted material determines whether the precursor drop just breaks up to form small droplets or it is effectively stretched to form a fiber. Therefore, the evolution of the process involves a proper balance between a low viscosity to allow the stretching of the fluid filament and high viscosity to surface tension ratio to avoid break up by capillary forces. So far, these two factors were studied as totally dependent on each other. However, Parikh [5] reports the chance of changing the surface tension of glasses regardless of viscosity by controlling the relative humidity of the atmosphere. Accordingly, in the present work, we outline an extensive experimental research on the productivity of Laser Spinning and, in

particular, on the influence of the relative humidity value of the assist gas on the produced fibers.

An extensive study on the working conditions of the process by varying the laser power and the advance precursor material was performed. The study was divided in two steps, both carried out with dry air: in the first one we have gotten the mass of obtained fibers per unit length of precursor material with the aim of optimize the efficiency of the process (figure 1). Then, we fixed the laser power in the optimal and varied the advance speed to obtain the distribution of final diameters of fibers produced as a function of this speed. These diameters were measured by using a Scanning Electron Microscope (SEM) (figure 2). We have carefully analyzed the resulting data trying to optimize the entire process. It led to an improvement in the efficiency and a better control in the final diameter of the fibers by just setting the suitable working conditions.

Then, we carried out an analysis on the influence of the surface tension of the melted volume by varying the relative humidity of the assist gas. The optimal values of laser power and sample speed were used now to perform it. We varied the relative humidity between 20 and 110 % (supersaturated) and measure the mass of obtained fibers per unit length of precursor material. As the main outcome, we have successfully increased this mass up to a 300 % by controlling the humidity of the assist air jet.

In summary, we optimized the working conditions of the process to maximize its productivity and to achieve a better control of the final diameter of the fibers. Moreover, we have demonstrated the relative humidity as an important parameter to optimize the process

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Acknowledgements: This work was partially supported by Xunta de Galicia (10DPI303014PR, CN2012/292), and by ERDF through Atlantic Area Transnational Cooperation Programme Project MARMED (2011-1/164).

References [1] F. Quintero, J. Pou, F. Lusquiños and A. Riveiro, Applied surface science 254, 4 (2007) 1042.

[2] F. Quintero, O. Dieste, J. Pou, F. Lusquiños and A. Riveiro, Journal of Physics D: Applied Physics 42, 6 (2009).

[3] F. Quintero, J. Pou, R. Comesaña, F. Lusquiños, A. Riveiro, A. B. Mann, R. G. Hill, Z. Y. Wu and J. R. Jones, Advanced Functional Materials 19, 19 (2009) 3084.

[4] O. Dieste, F. Quintero, J. Pou, F. Lusquiños and A. Riveiro, Applied Physics A: Materials Science and Processing 104, 4 (2011) 1217.

[5] N. M. Parikh, Journal of the American Ceramic Society 41, 1 (1958) 18.

Figure 1: Graph showing the productivity of the Laser Spinning process. The mass per unit length as a function of the laser power and the sample speed is plotted.

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Figures

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Figure 2: SEM images showing the way to measure the diameters of the fibers. They were obtained with a laser power of 2 kW and a sample speed of 600 mm/s with dry air.

Oral Novel mechanical properties of graphene using atomic force microscopy

1 2

mick@AsylumResearch.co.uk

Asylum Research, an Oxford Instruments Company, Bicester, UK Asylum Research, an Oxford Instruments Company, Santa Barbara, CA USA

Graphene was first synthesized [1], [2] in 2004 and since then, research into graphene and related materials has grown extremely rapidly, notably earning a Nobel prize in 2010. The juxtaposition of impressive mechanical, electrical and thermal properties makes these materials likely candidates for disruptive technological breakthroughs, in fields spanning high performance and quantum computing, energy collection and storage, and novel sensors and detectors. They have specific applications in spintronics, as single‐molecule sensors and terahertz oscillators, in nanoelectromechanical systems (NEMS), and as transparent electrodes for use in touch-screen displays and photovoltaics. They also offer potential successors to silicon that may take us beyond Moore's law.

Atomic Force Microscopy (AFM) is uniquely positioned to provide structural, mechanical, optical and electrical characterization of graphene and related two--‐dimensional materials, allowing us to probe their structure, properties and function. Here, we will discuss recent results from selected AFM techniques applied to graphene: amplitude-modulation frequency-modulation (AMFM), loss-tangent mapping and friction force microscopy (FFM).

AM-FM and loss tangent imaging [3] can be used together to give complementary information about local stiffness and energy dissipation. Briefly, the cantilever is driven at first two flexural resonances. Recently, a number of multifrequency AFM schemes have been proposed to improve high resolution imaging, contrast, and quantitative mapping of material properties.[4], [5] [6], [7] Bimodal imaging using more than one resonant vibrational mode of the cantilever simultaneously.

The resonant modes can be treated as

250

Mick Phillips1 2 R. Proksch

independent “channels” with each having separate observables. The two examples shown here illustrate nanomechanical contrast. The somewhat surprising results will be interpreted in terms of long range conservative interactions and short range dissipative interactions.

FFM allows clear and easy discrimination between graphene and an underlying substrate. We will present data to demonstrate this, and how high resolution FFM can be used to reveal the relative orientation of graphene flakes, providing insight into graphene growth processes [8].

References [1] K. S. Novoselov, A. K. Geim, S. V.Morozov, D. Jiang, Y. Zhang, S. V. Dubonos, I. V. Grigorieva, and A. A. Firsov, Electric field effect in atomically thin carbon films, Science, 306(5696):666–669 (2004).

[2] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, M. I. Katsnelson, I. V. Grigorieva, S. V. Dubonos, and A. A. Firsov, Nature, 438(7065):197–200 (2005).

[3] R. Proksch, and D. Yablon, Appl. Phys. Lett.

100(7), 073106 (2012).

[4] M. Stark, R. W. Stark, W. M. Heckl and R. Guckenberger, Proc. Natl. Acad. Sci 99, 8473 (2002).

[5] T. R. Rodriguez and R. Garcia, Appl. Phys. Lett.

84, 449 (2004).

[6] Proksch, Appl. Phys. Lett. 89, 113 121 (2006).

[7] N. F. Martinez, S. Patil, J. R. Lozano, and R. Garcia, Appl. Phys. Lett. 89, 153 115 (2006).

[8] A. J. Marsden, M. A. Phillips and N. R. Wilson, Friction force microscopy: a simple technique for identifying graphene on rough substrates

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and mapping the orientation of graphene grains on copper, http://arxiv.org/abs/1302.0177, (2013).

Figures

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Figure 2: Friction force images of graphene grown on copper by chemical vapour deposition. The graphene flakes can be readily distinguished from the copper by their low friction. At smaller scan sizes, the graphene lattice can be resolved clearly.

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Figure 1: Graphene on SiO2. (a) topography, (b) AM--窶色M and (c) loss tangent images of a graphene on SiO2. Note that the graphene appears less stiff than the substrate. The edge layers exhibit a larger loss tangent, indicative perhaps of water trapped between the graphene and SiO2.

Oral Understanding Colloidal Nanoparticle Growth

Joerg Polte

joerg.polte@hu-berlin.de Humboldt University to Berlin, Brook-Taylor-Strasse 2, 12489, Berlin Germany

252

Colloidal nanoparticles have attracted much attention due to their unique properties and promising applications. Synthetic procedures are known and have been investigated since Faraday’s groundbreaking experiments about gold colloids more than 150 years ago.[1] However, a profound understanding of the underlying nanoparticle formation processes is still missing.[2] Recently, we introduced novel setups and techniques which enable the determination of the size evolution and concentration of colloidal nanoparticles throughout the growth process.

These technical developments have been the key to determine the growth mechanisms of several metal colloid syntheses. [3]-[6] The comparison of the different mechanisms reveals fundamental principles of nanoparticle growth that are in contrast to present nucleation and growth theories. For the investigated systems it was shown that growth is only governed by colloidal stability whereas a process of nucleation has no significant effect on the final particle size distribution. Instead, a novel model is presented that provides a comprehensive understanding of the fundamental principles of colloidal nanoparticle growth.

Exemplified for gold, silver and palladium nanoparticles, it will be demonstrated that the gained mechanistic knowledge allows improving and developing strategies for size controlled syntheses of nanoparticles without additional stabilizing agents.

In summary, three major issues in colloidal science are addressed: (i) experimental techniques and methods to investigate nanoparticle formation processes in-situ and time resolved; (ii) fundamental principles of nanoparticle growth deduced from mechanistic information of several

nanoparticle syntheses;(iii) precise size control of colloidal metal nanoparticles.

References [1] M. Faraday, Philosophical Transactions of the Royal Society of London, (1857), 147.

[2] Y. Xia, Y. Xiong, B. Lim, and S. E. Skrabalak, Angewandte Chemie International Edition, (2009), 48, 1, 60.

[3] J. Polte, F. Emmerling, M. Radtke, U. Reinholz, H. Riesemeier, and A. F. Thünemann, Langmuir, (2010), 26, 8, 5889.

[4] J. Polte, T. T. Ahner, F. Delissen, S. Sokolov, F. Emmerling, A. F. Thünemann, and R. Kraehnert, J. Am. Chem. Soc., (2010), 132, 4, 1296.

[5] J. Polte, R. Erler, A. F. Thünemann, F. Emmerling, and R. Kraehnert, Chem. Comm., (2012), 46, 48, 9209.

[6] J. Polte, X. Tuaev, M. Wuithschick, A. Fischer, A. F. Thuenemann, K. Rademann, R. Kraehnert, and F. Emmerling, ACS Nano, 6, (2012), 5791.

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Invited Coulomb Blockade of shot noise

1

Fabien Portier 1,2 1 C. Altimiras , O. Parlavecchio 1 1 P. Joyez , P. Roche D. Vion1 and 1 D. Estève

1

SPEC/IRAMIS/DSM/CEA Saclay, URA CNRS 2464, 91191 Gif-sur-Yvette Cedex, France present address: NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa, Italy 2

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observed corrections to the shot noise with the help of an extension to the DCB theory. The methods developed here is applicable to widely used quantum components such as point contacts and quantum dots.

Keywords: Coulomb blockade, high frequency noise, Josephson arrays

Related work

Figures

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[1] Experimental Test of the High-Frequency Quantum Shot Noise Theory in a Quantum Point Contact, E. Zakka-Bajjani et al., Phys.

Rev. Lett. 99, 236803 (2007).

[2] Bright Side of the Coulomb Blockade, M. Hofheinz et al., Phys. Rev. Lett. 106, 217005 (2011).

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Unlike for classical electronic component, the transport properties of a quantum component are not intrinsic and depend on its embedding circuit.

This originates from the probabilistic character of quantum transmission of individual electrons through the device, which results in a broad-band current noise called shot noise.

When the impedance of the embedding circuit becomes comparable to the resistance quantum h/e^2, shot noise effectively excites its electromagnetic modes, and electronic transfer becomes inelastic.

This modifies electrical transport, a phenomenon called Dynamical Coulomb Blockade (DCB).

Experimental investigations of this environment feedback have so far been limited to dc conductance measurements, and a complete description of quantum transport, including the current and its fluctuations in the presence of DCB is still lacking. In this work, we have embedded a tunnel junction in a microwave quarter-wave resonator which implements a "single-mode" electromagnetic environment. With such circuit, we can both measure the I(V) characteristic of the junction and the shot noise emitted by the junction at microwave frequencies (~6GHz).

Obtaining strong DCB effects requires the resonator to display a characteristic impedance comparable to the resistance quantum (h/e^2~26kOhm), which is hardly achievable by exploiting plain geometric considerations. We have taken advantage of the kinetic inductance of an array of Josephson junctions, to increase up to ~1.5 kOhm the characteristic impedance of an otherwise standard coplanar waveguide. The resulting coupling is strong enough to observe DCB corrections to the shot noise emitted by the tunnel junction, interpreted as spontaneous two-photon emission processes. We can reproduce the

Invited Charge Transport and Magneto Electric Sub-bands in 1D Nano-Objects

Bertrand Raquet

Laboratoire National des Champs Magnétiques Intenses – Toulouse, LNCMI-T UMR 3228, CNRS, UPS, INSA, Université de Toulouse, France.

254

1D nano-objects like carbon nanotubes (CNT), graphene nano-ribbons (GNR) or semiconducting nanowires (sc-NWs) display remarkable electronic transport properties driven the electronic confinement at nano-scale. Their electronic band structure result in a set of 1D sub-bands with van Hove singularities in the density of states. The charge density is controlled by an electrostatic gate and a spin manipulation is envisaged in some of these materials by playing with either the spinorbit coupling like in sc-NWs or by taking advantage of the edge states in GNR. These remarkable properties open new routes for the future of the nanoelectronics, with potential applications in the field of high frequency transistors, digital logic devices, electronic wave guides or sensors.

However, a deep characterisation of the electronic band structure of an individual nano-object remains challenging.

In this talk, I will give experimental evidence that the electronic band structure of a single 1D nanoobject can be directly addressed by electronic transport measurements, in the open quantum dot regime, and under extreme conditions of magnetic fields and temperatures. After a brief review of magneto-fingerprints of the 1D sub-bands in carbon nanotubes and in graphene nanoribbons [1], I will present recent (magneto)-transport results obtained on 303 nm diameters InAs NWs. At zero-magnetic field, the low temperature conductance versus a back-gate voltage, G(Vg), reveals some step-like modulations, signature of the presence of van Hove singularities in the density of state. An accurate control of the number of conducting channels is therefore possible as a function of the electrostatic doping. The magnetoconductance measurements under 60T exhibit giant variations of the conductance mediated by the doping level. In particular, when only a few

sub-bands participate to the electronic transport, a complete switch-off of the conductance is evidenced under both a parallel and a magnetic field. Our simulations of the electronic band structure of InAs NWs in the Landau regime (for a magnetic length smaller than the NW radius) demonstrate that the magneto-conductance behaviour brings direct signatures of the onset the magneto-electric sub-bands. The conductance switch–off in high field is assigned to the electronic depopulation. We finally speculate on the full spin polarisation of charge carriers in the lowest occupied Landau states due to the large effective g-factor.

References [3] B. Lassagne & al, Phys. Rev. Lett. 98, 176802 (2007); S. Nanot & al, C. R. Physique 10 (2009); B. Raquet & al, Phys. Rev. Lett. 101, 046803 (2008); S. Nanot & al, Phys. Rev. Lett. 103, 256801 (2009); J-M Poumirol et al, Phys. Rev. B 82, 041413(R) (2010) ; R. Ribeiro & al., Phys.

Rev. Lett. 107, 086601 (2011).

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Oral

CIC microGUNE, Goiru Kalea 9 Polo Innovación Garaia, 20500 Arrasate-Mondragón, Spain 2 Micro and Nano Fabrication Unit, IK4-Tekniker, C/ Iñaki Goenaga 5, 20600 Eibar, Spain 3 Dpto. de Física, Ingeniería de Sistemas y Teoría de la señal and Instituto Universitario de Materiales de Alicante (IUMA), Universidad de Alicante, 03080 Alicante, Spain 4 Dpto. de Física Aplicada and IUMA, Universidad de Alicante, 03080 Alicante, Spain 5 Dpto. de Óptica and IUMA, Universidad de Alicante, 03080, Alicante, Spain

Organic solid-state lasers (OSLs) have been widely investigated due to the advantages of easy processability, chemical versatility, wavelength tuneability and low cost offered by organic materials [1,2]. Among the various types of OSLs reported in the literature, distributed feedback (DFB) lasers have been particularly successful [1,2], since they present several advantages, such as easy deposition of the organic film, low thresholds, single mode emission and no need of mirrors. So, today they are being used to developed applications in the fields of telecommunications [2], biosensing and chemical sensing [3,4]. Among the methods generally used for grating engraving, nanoimprint lithography (NIL) [5] is one of the most promising technologies, even for future industrial applications, due to its high throughput, high resolution (sub-10 nm) and low cost. From the materials point of view, a wide variety of materials has been used to fabricate the active layers of organic DFBs [1]. Among them, in the last years our group has focused in polystyrene (PS) films doped with perylenediimide derivatives (PDIs), mainly due to their excellent thermal and photostability properties, as well as their high photoluminescence quantum efficiencies. We recently reported [6] low-threshold and highly photostable (under ambient conditions) DFB lasers. In these DFB lasers, DFB gratings were fabricated by thermal-NIL on a resist, then transferred to the SiO2 substrate and finally, the active medium was spin-coated over the gratings.

Threshold and operational lifetime of the DFB laser devices are influenced by the excitation area, so in this presentation we report on the influence of the excitation area on both the threshold and operational lifetime of 1D second-order DFB lasers based on PS films doped with the N,N’-di-(1-

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1,2

A. Juarros1,2 D. Otaduy1,2, S. Merino1,2 E.M. Calzado3, J.M. Villalvilla4 P.G. Boj5, J.A. Quintana5 V. Navarro-Fuster4 and M.A. Díaz-García4

aretolaza@cicmicrogune.es

hexylheptyl) perylene-3,4:9,10-tetracarboxylic diimide (PDI-C6) as active material [7]. The DFB gratings with depths of 120 nm and 400 nm were fabricated by NIL as mentioned before, and a film of 600 nm thickness active medium was spincoated over the gratings. The shape of the excitation area was elliptical (Figure 1) and its size was varied from 0.008 to 2.9 mm2. The laser thresholds of the DFB devices were measured and expressed as energy per pulse, energy density and power density (Figure 2). Effectiveness of reducing the thresholds, when expressed in energy per pulse units, by reducing the area of the excitation beam over the sample was proved (Figure 2a).

However, the functionality of data obtained with small excitation areas couldn’t be properly determined from this figure. So, the threshold was expressed as energy or power density (Figure 2b).

In this case, increase of threshold was observed for excitation areas below a certain area, denoted as critical area (Acrit) ( 0.1 mm2 in this work). With respect to the operational lifetime, when excitation was performed with spot areas larger than Acrit, similar lifetimes (around 300 min) were obtained. On the other hand, as can be seen in Figure 3, when very small areas (below Acrit) were used, lifetimes became drastically reduced (lifetimes of only 15 min for excitation areas of 0.08 × 10-3 cm2).

Acknowledgements: This work has been funded by the “Ministerio de Ciencia e Innovación” through the grant MAT2011-28167-C02.

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1

Aritz Retolaza

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Pump size dependence of organic second-order distributed feedback lasers

References [1] D.W. Samuel, G.A. Turnbull, Chem. Rev., 107 (2007) 1272.

[2] J. Clark, G. Lanzani, Nat. Photonics, 4 (2010) 438.

[3] M. Lu, S.S. Choi, C.J. Wagner, J.G. Eden, B.T. Cunningham, Appl. Phys. Lett., 92 (2008) 261502.

[4] M.B. Christiansen, J.M. Lopacinska, M.H. Jakobsen, N.A. Mortensen, M. Dufva, A. Kristensen, Opt. Express, 17 (2009) 2722.

[5] S.Y. Chou, P.R. Krauss, P.J. Renstrom, Appl.

Phys. Lett. 67 (1995) 3114.

[6] V. Navarro-Fuster, E.M. Calado, P.G. Boj, J.A. Quintana, J.M. Villalvilla, M.A. Díaz-García, V. Trabadelo, A. Juarros, A. Retolaza, S. Merino, Appl. Phys. Lett., 97, (2010) 171104.

[7] E.M. Calzado, J.M. Villalvilla, P.G. Boj, J.A. Quintana, V. Navarro-Fuster, A. Retolaza, S. Merino, M.A. Díaz-García, Appl. Phys. Lett.

101, (2012) 223303.

Figure 3: Normalized laser intensity versus irradiation time (bottom axis) and versus the number of pump pulses (10 ns, 10 Hz; top axis) for a DFB device with d = 400 nm, under excitation with areas below and above Acrit  1 × 10-3 cm2, at pump power densities two times above the corresponding thresholds (215 and 47 kW/cm2, respectively).

Figures

Figure 1: Sketch of the excitation geometry.

256

Figure 2: Laser thresholds for DFB devices with two grating depths (d = 120 nm and d = 400 nm) as a function of the excitation area over the sample expressed as a) energy per pulse, and b) energy density (right axis) and power density (left axis).

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Oral Synthesis of silver nanoparticles from seed washings and their antibacterial activity

Alan Reynolds M. Zahid Qureshi A. Hiralal and N. Verma

Experimental Techniques Centre, Brunel University, London, UK

qureshienv@yahoo.com

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have certain silver particles attached to their body [Fig.6].

[1] Baia, L. and Simon, S. Modern Research and Educational Topics in Microscopy, Vol 1(2007) 576.

[2] Liu, W., Wu, Y., Wang, C., Li, H.C., Wang, T., Liao, C.Y., Cui, L., Zhou, Q.F., Yan, B. and Jiang, G.B. Nanotoxicology, vol. 4, no. 3, (2010) 319330.

[3] Mahl, D., Diendorf, J., Ristig, S., Greulich, C., Li, Z.-, Farle, M., KĂśller, M. and Epple, M. Journal of Nanoparticle Research, vol. 14, no. 10, (2012) 1-13.

[4] Morones, J.R., Elechiguerra, J.L., Camacho, A., Holt, K., Kouri, J.B., RamĂ­rez, J.T. and Yacaman, M.J. Nanotechnology, vol. 16, no. 10, (2005) 2346-2353.

[5] Roopan, S.M., Rohit, Madhumitha, G., Rahuman, A., Kamaraj, C., Bharathi, A. and Surendra, T.V. Industrial Crops and Products, vol. 43, no. 1, (2013) 631-635.

Figures

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References

Figure 1: Show the UV-visible spectrum of the formation of AgNPs with seed F-1. The absorbance peak is reached at 444 nm for AgNPs.

257

In the recent years metallic nanoparticles have been extensively studied for their use in a number of products due to their chemical, physical and biological properties [1]. Silver nanoparticles have gained special importance due to their uses in the medical sector for wound dressings and surgical equipments, due to their antimicrobial properties [2,3]. This paper presents novel, green and low cost formation of silver nanoparticles and studies on their antibacterial potential [4,5]. The formation of silver nanoparticles is monitored via the change of colour occurring due to the surface plasmon resonance using the UV-Visible spectrometer. The results achieved showed that silver nanoparticles began forming within an hour of the reaction starting and a brown colour of the solution can be appreciated after a few hours.

Characteristics of these nanoparticles have been determined via the use of SEM, TEM and X-ray analysis in order to establish the qualitative and quantitative measurements of the particles. The silver nanoparticles formed were of about 20 nm in size and well dispersed; showing capping agents were preventing the nanoparticles from agglomerating. Antibacterial properties have also been investigated using Bacillus subtilis. Growth of the bacteria was monitored by the change in turbidity of the nutrient broth by noting absorbance at 600nm using a UV-Visible spectrometer. The effect of the nanoparticles in bacteria was determined via the control of the concentration of the nanoparticles against the turbidity, and therefore growth, of the bacteria.

This determined the inhibition of the bacteria when in solution with silver nanoparticles [Fig.5].

In order to determine the effect of the nanoparticles in bacteria, the cells were viewed under the SEM and it was found that dead cells

Figure 2: SEM image of AgNPs formed using seed F-1 at magnification of X 100 000.

Figure 6: Show SEM image of Bacillus in silver nanoparticles.

Figure 3: Show the JPEG image by TEM for AgNPs with seed F-1.

Figure 4: Show the X-Ray diffraction confirming the presence of Silver NPs.

258

Figure 5: show the UV-visible spectrum of the growth of Bacillus subtilis in nutrient broth with increasing concentrations of silver nanoparticles.

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Invited

Biomolecular hydrogels - from supramolecular structure and dynamics to biological function

Ralf P. Richter

rrichter@cicbiomagune.es I2BM, Department of Molecular Chemistry, J. Fourier University, Grenoble, France CIC biomaGUNE, Biosurfaces Unit, San Sebastian, Spain Max-Planck-Institute for Intelligent Systems, Stuttgart, Germany

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To illustrate this concept, I will present a few examples of our recent research. They relate to (i) a nanoscopic protein hydrogel inside living cells that is responsible for the regulation of all macromolecular transport into and out of the nucleus [1] (Figure 1), (ii) microscopic hydrogel-like assemblies that are made from polysaccharides of the glycosaminoglycans family and their binding partners and that are involved in various physiopathological process such as inflammation, fertilization, cancer progression and immune response [2, 3, 4]. Our results may ultimately prove useful for the development of novel bioinspired devices, such as size and species selective filtration devices, or advanced biosensors, and for the development of novel diagnostic or therapeutic methods.

[1] N. B. Eisele, S. Frey, J. Piehler, D. Görlich and R. P. Richter, Ultrathin nucleoporin FG repeat films and their interaction with nuclear transport receptors. EMBO Rep., 11 (2010), 366-372.

[2] R. P. Richter, K. K. Hock, J. Burkhartsmeyer, H. Boehm, P. Bingen, G. Wang, N. F. Steinmetz, D. J. Evans and J. P. Spatz, Membrane-Grafted Hyaluronan Films: a Well-Defined Model System of Glycoconjugate Cell Coats. J. Am. Chem. Soc., 127 (2007), 5306-5307.

[3] N. S.Baranova, E. Nilebäck, F. M. Haller, D. C. Briggs, S. Svedhem, A. J. Day, R. P. Richter, The Inflammation-Associated Protein TSG-6 CrossLinks Hyaluronan via Hyaluronan-Induced TSG6 Oligomers. J. Biol. Chem. 286 (2011), 2567525686.

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References

259

Nature has evolved complex materials that are exquisitely designed to perform specific functions.

Certain proteins and glycans self-organize in vivo into soft and dynamic, strongly hydrated gel-like matrices.

Illustrative examples of such biomolecular hydrogels are cartilage or mucus.

Even though biomolecular hydrogels are ubiquitous in living organisms and fulfill fundamental biological tasks, we have today a very limited understanding of their internal organization, and how they function. The main reason is that this type of assemblies is difficult to study with conventional biochemical methods.

In order to study biomolecular hydrogels directly on the supramolecular level, we have developed an unconventional approach that draws on knowledge from several scientific disciplines.

Exploiting surface science tools, we immobilize one or several types of biomolecules (proteins, lipids and carbohydrates) on solid supports (typically gold, silica or glass) – with tight control on the distribution, mobility and molecular orientation.

The functionalized surfaces serve as templates to self-assemble model films with thicknesses in the nanometer range from purified components. With a toolbox of biophysical characterization techniques, including quartz crystal microbalance (QCM-D), spectroscopic ellipsometry (SE), atomic force microscopy (AFM) and reflection interference contrast microscopy (RICM), these model hydrogels can be investigated in aqueous environment, quantitatively and in great detail.

The experimental data, combined with polymer theory, allow us to develop a better understanding of the relationship between the supramolecular organization and dynamics of biomolecular hydrogels, their physico-chemical properties and their biological function.

[4] S. Attili, O. V. Borisov, R. P. Richter, Films of end-grafted hyaluronan are a prototype of a brush of a strongly charged, semi-flexible polyelectrolyte with intrinsic excluded volume.

Biomacromolecules 13 (2012), 1466-1477.

Figures NTR

Ran GTP

NTR NTR

cargo

FG repeat domains

NTR NTR

cargo

NTR NTR

Ran GTP

solid support

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Figure 1: Macromolecular transport between the cellâ&#x20AC;&#x2122;s nucleus and the cytosol occurs through nuclear pore complexes (NPCs). The transport is selective: objects (cargo) beyond a certain size (30 kDa) need to attach to soluble nuclear transport receptors (NTRs) in order to be channeled efficiently through the pore. A supramolecular assembly of specialized and natively unfolded protein domains within the NPC is thought to be the key component of the NPC´s permeability barrier. The mechanism behind transport selectivity is at present only poorly understood. We have developed ultrathin FG repeat domain films as a surface-confined model system of the permeability barrier. In this contribution, we will present how such model systems can provide insight into the mechanism of transport across the permeability barrier. .

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Invited

INL - International Iberian Nanotechnology Laboratory. Avenida Mestre José Veiga 4715-330 Braga.Portugal 2 Laboratory of Magnetism and Nanotechnology (NANOMAG). Research Technological Institute.University of Santiago de Compostela. E-15782 Santiago de Compostela, Spain 3 Conservative Dentistry. Faculty of Medicine and Dentistry. University of Santiago de Compostela E15782 Santiago deCompostela, Spain

Magnetic particles play nowadays an important role in different technological areas with potential applications in fields such as electronics, energy and biomedicine [1, 2]. The production of monodisperse magnetic nanoparticles (NPs) down to few atoms is one of the most important challenges in Nanotechnology. The microemulsion technique is a powerful method to prepare simple metallic and oxide NPs, as well as, core-shell and “onion-like” NPs [3]. Although microemulsions cannot be considered as real templates, they constitute an elegant technique, which can provide a very good control of the final particle size. The reason for that is complex interplay mainly between three parameters, namely, surfactant film flexibility, reactant concentration and reactant exchange rate [4]. By adequately choosing these three parameters one can get a homogeneous distribution of particle sizes down to few atoms.

Metal atomic clusters consist of groups of atoms (usually less than 100-200) with well-defined compositions and one or very few stable geometric structures. They represent the most elemental building blocks in nature – after atoms – and are characterized by their size (below circa 1-2 nm) [5].

Below such size range the free electrons of the metal nanoparticles become frozen and the metals lose their metal behavior, which is clearly detected by the disappearance of the characteristic plasmon bands of the metals. This size scale is comparable to the Fermi wavelength of an electron, which makes them a bridge between atoms and nanoparticles or bulk metals. Novel and fascinating properties, which strongly differ in many cases from the properties of bulk and nanoparticles of the same material, appear at this nanometer/subnanometer transition. For example, fluorescence [6], catalysis [7], magnetism [8], and circular

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jose.rivas@inl.int

dichroism [9] have been found in such clusters, which are not exhibited for the same material in larger sizes. In such range, a bandgap is opened at the Fermi level, increasing the magnitude of the gap as the cluster size is reduced. Due to this bandgap, which can be as high as 3 to 4 eV for the smallest clusters having only 2 to 3 atoms, and the extra-stabilization by electronic closing shells, clusters –contrary to the general belief- are very stable. However, studies involving metallic clusters are still very limited because of the procedures used for their synthesis. Only very small amounts of highly polydisperse samples can be obtained after difficult separation procedures. In the last years we developed, among others, novel microemulsion-based methods for the synthesis of clusters, which allows their production with relatively good monodispersity [10, 11].

In this talk we will describe the microemulsion synthesis procedure, focussing on some particular examples showing how the magnetic properties of materials change from particles to atomic clusters.

Moreover, special emphasis will be done on different applications of nanoparticles and clusters related to the biomedical field. In particular, biocompatible iron oxide nanoparticles are being increasingly used as heating sources in magnetic hyperthermia, since they fulfill the chemical and physical requirements to allow treating more efficiently tumoral tissues by means of magnetically induced heat under an oscillating magnetic field [12]. This remotely controlled temperature increases are also very interesting for thermally induced growth factors release systems in bone regeneration applications [13-15]. On other hand, although nanotechnology is already being applied successfully in dentistry through the use of nanocomposite materials such as adhesives,

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Jose Rivas 1 M. Bañobre-López , 2 Y. Piñeiro-Redondo , B. Rivas3 and 3 M. A. López-Quintela .

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Magnetic particles and clusters through a cross-disciplinary approach

cements and resins, we will introduce the use of subnanometric metallic clusters as potential antimicrobial agents in dental applications

References

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[1] Reiss G. and Hütten A. Nature Materials 4, 725 - 726 (2005).

[2] Gao J., Gu H. and Xu B. Accounts of chemical research 42 (8), 1097-1107 (2009).

[3] See e.g. López-Quintela M.A. and Rivas, J. J. Colloid Interface Sci. 1993, 158, 446; Ibid, Curr.Opìnion Colloid Interface Sci. 1996, 1, 806; López-Quintela M.A., Rivas J., Blanco M.C. and Tojo C. “Nanoscale Materials”, Ed. by L.M. Liz Marzán and P.V. Kamat. Kluwer Academic Plenum Publ., Chapter 6, 135-155 (2003).

[4] See e.g. López-Quintela, M.A. Curr. Opin.

Colloid Interface Sci., 8, 137 (2003).

[5] Calvo, J.; Rivas, J.and López-Quintela, M.A. Encyclopedia of Nanotechnology, Bhushan, Bharat (Ed.), Springer Verlag. 2639-2648 (2012).

[6] Zheng, J.; Zhang, C.; Dickson, R.M. Phys.Rev.Lett., 93, 77402 (2004).

[7] Vilar-Vidal, N; Rivas, J.; López-Quintela, M.A. ACS Catalysis, 2, 1693 (2012).

[8] Yamamoto Y., Miura T., Suzuki M., Kawamura N., Miyagawa H., Nakamura T., Kobayashi K., Teranishi T., Hori H. Phys.Rev.Lett., 93, 116801 (2004).

[9] Schaaff T.G., Whetten R.L., J.Phys.Chem.B, 104, 2630 (2000).

[10] Ledo-Suárez, A., Rivas, J., Rodríguez-Abreu, C.F., Rodríguez, M.J., Pastor, E., HernándezCreus, A., Oseroff, S.B., López-Quintela, M.A. Angew.Chem.Int.Ed., 46, 8823 (2007).

[11] Vázquez-Vázquez, C., Bañobre-López, M., Mitra, A., López-Quintela, M.A. and Rivas, J. Langmuir 25, 8208–8216 (2009).

[12] Rivas J., Bañobre-López M., Piñeiro-Redondo Y., Rivas B. and López-Quintela M. A. J. Magn.

Mater. 324, 3499-3502 (2012).

[13] Tampieri, A., D’Alessandro, T., Sandri, M., Sprio, S., Landi, E., Bertinetti, L., Panseri, S., Pepponi, G., Goettlicher, J., Bañobre-López, M. and Rivas, J. Acta Biomaterialia 8 (2), 843-851 (2012).

[14] Bañobre-López, M., Piñeiro-Redondo, Y., De Santis, R., Gloria, A., Ambrosio, L., Tampieri, A., Dediu, V. and J. Rivas. J. Appl. Phys. 109, 07B313 (2011).

[15] Gloria, A., Russo, T., Dámora, U., Zeppetelli, S., D´Allesandro, T., Sandri, M., Bañobre-Lopez, M., Pineiro-Redondo, Y., Uhlarz, M., Tampieri, A., Rivas, J., Herrmannsdorfer, T., Dediu, V. A., Ambrosio, L. and De Santis, R. J.R.Soc. Interface, 10, 20120833 (2013).

Figure

Figure : Scheme about the use of magnetic nanoparticles in bone regeneration applications by using magnetic hyperthermia.

European Community’s FP7 under grant agreement no. NMP3-LA2008-14685 project MAGISTER (www.magister-project.eu).

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Oral Femtosecond Laser Induced Periodic Surface Nanostructuring of Platinum Thin Films

1

Ainara Rodríguez 1 M. C. Morant-Miñana 1,2 A. Arriola and S. M Olaizola1,2 airodriguez@cicmicrogune.es

1

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layer and 5 nm of Cr buffer layer. A Ti: Sapphire laser system consisting of a mode-locked oscillator and a regenerative amplifier was used to generate 100 fs pulses at a central wavelength of 800 nm with a 1 kHz repetition rate. The 12 mm-diameter laser beam was focused on the sample using a 10x microscope objective with a NA of 0.3.

A study of the processing parameters on the formation of surface nanostructures was performed by processing a map of irradiated areas, as detailed in Table 1. The laser beam linearly scanned the target area (0.5 x 0.25 mm2) at a constant speed for different horizontal displacements (Δx). Laser fluence was varied by adjusting the defocusing distance Z, i.e., the distance between the Pt surface and the laser focal plane. A variation of the scanning speed results in a modification of the number of overlapped pulses. For a 1 Khz repetition rate, scanning speeds (v) from 0.1 to 1.0 mm·s-1 correspond to a number of 10 to 100 overlapped pulses. Light polarization was adjusted using a zero-order half-wave plate.

Scanning Electron Microscopy was used to analyze the influence of the irradiation conditions on the generated nanostructures. FE-SEM micrographs revealed that both Low-Spatial Frequency LIPSS (LSPL) with a period of about 600 nm and HighSpatial Frequency LIPSS (HSFL) with a period around 200 nm can be generated in Pt thin films for specific irradiation conditions (see Figure 1).

HSFL appear for high scan speeds (Figure 1.a, 1.d, 1.g) while LSFL are predominant for low scan speeds (Figure 1.c, 1.f, 1.i); for intermediate speeds, both types of structures coexist (Figure 1.b, 1.e, 1.h). Additionally, periodic structures are better defined as laser fluence decreases, as can be deduced from Figures 1.b and 1.e. Therefore, in order to obtain large areas well covered with HSFL,

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The ability to fabricate structures on the nanoscale with high precision and in a wide variety of materials is a crucial issue for the development of the nanoscience and nanotechnology. High resolution lithographic techniques such as electron-beam lithography or EUV lithography, although very accurate and reproducible, usually suffer from low throughput and high operation costs. In this context, laser micro- and nanostructuring techniques are getting increased interest for this purpose. In the last years, femtosecond laser surface nanostructuring has emerged as a novel and versatile technology for producing a wide variety of nanostructured materials for applications such as photonics, plasmonics, optoelectronics, biochemical sensing, micro/nanofluidics, optofluidics, biomedicine, and other areas. Among the entire femtosecond laser induced surface structuring techniques, Laser Induced Periodic Surface Structures (LIPSS) stands out as one of the most actively studied approaches [1]. Although these structures have been observed in a wide range of materials including semiconductors, dielectrics and metals [2-4], these last are of particular interest due to their applications in photonics and sensing. Intense research work has been performed to study the formation of LIPSS on bulk metals [4-6]. However, the optimal conditions for a controllable nanostructuring of metallic thin films using femtosecond laser ablation technique are still unexplored. In this work we present a systematic study of the formation of LIPSS on the surface of Pt thin films as a function of the laser irradiation parameters.

Pt films with a thickness of 200 nm were deposited

by DC-magnetron Sputtering onto Si (100) substrates with a 1.2 µm thermally grown SiO2

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CIC microGUNE, Goiru Kalea 9 Polo Innovación Garaia, 20500 Arrasate-Mondragón, Spain 2 Ceit-IK4 & Tecnun (University of Navarra), Miguel Lardizábal 15, 20018 San Sebastián, Spain

a compromise between laser fluence and scan speed must be achieved. For this particular case, a defocusing distance of 120 µm and a scan speed of 0.3 mm·s-1 with a line separation of 10 µm seems to be the optima processing conditions.

Micrographs also revealed the influence of the beam polarization on the orientation of the generated nanostructures: HSFL appear oriented along the polarization direction of the beam, while LSFL are perpendicular to the polarization vector.

It can be concluded that both 600 nm LSFL and 200 nm HSFL periodic relieves with controlled orientation can be precisely generated by femtosecond lasers on Pt thin films by properly selecting the irradiation parameters: laser fluence, polarization and scan speed. These nanostructured films are of particular interest for applications requiring an increased active surface, such as miniaturized sensors and surface assisted laser desorption/ionization.

Figures

Figure 1: FE-SEM micrographs of the resulting LIPSS on Pt films for different rradiation conditions and horizontal displacement of 10 µm.

References [1] Vorobyev, A.Y., Guo, C., Laser & Photon Rev (2012) 1-23.

[2] Tomita T., Kinoshita K., Murai T., Fukumori Y., Matsuo S., Hashimoto S., Journal of Laser Micro Nanoengineering Vol. 2, No. 2, (2007) 141-145.

[3] J. Bonse, J. Krüger, S. Höhm, A. Rosenfeld, J. Laser Appl., Vol. 24, No. 4, (2012) 042006.

[4] Hwang T.Y., Guo C., J. Appl. Phys. 108 (2010) 073523.

[5] Djouder M., Itina T.E., Deghiche D., Lamrous O., Applied Surface Science 258 (2012) 2580– 2583.

[6] Bizi-Bandoki P., Benayoun S., Valette S., Beaugiraud B., Audouard E., Applied Surface Science 257 (2011) 5213–5218.

Table 1

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Laser irradiation parameters used for Pt nanostructuring

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Oral

Dpt. Física Materia Condensada, Universidad del País Vasco, Facultad de Ciencia y Tecnologia, Apdo. 644, 48080 Bilbao, Spain.

2 Dpt. Física Aplicada II, Universidad del País Vasco, Faciultad de Ciencia y Tecnologia, Apdo. 644, 48080 Bilbao, Spain.

3 FEI, Achtseweg Noord 5, 5651 GG, Eindhoven, the Netherlands

Introduction Recently, there has been growing interest in the potential use of shape memory alloys (SMA) in micro and nano-scale structures and devices, for example as sensors or actuators in micro electromechanical systems (MEMS). With a growing worldwide market in excess of hundred billion dollars, MEMS constitute a new paradigm of technological development for the present century, and smart materials are converging with miniaturization technologies, enabling a new generation of smart MEMS or SMEMS. Among the different smart materials targeted for use in SMEMS, shape memory alloys have attracted considerable interest [1] because they offer the highest output work density, about 107 J/m3 [2], and exhibit specific desirable thermo-mechanical effects such as superelasticity and shape memory.

Most of the research effort is being focused on thin films [3] and with a view to reliable application of these materials, their shape memory and superelastic properties should be carefully characterized at small scales, and one possible approach relies on instrumented nanoindentation techniques. However, the multiaxial nature of deformation around the nanoindenter renders quantitative interpretation of the data very complex, especially for SMAs, which exhibit strongly non-linear behaviour during thermal or stress-induced transformation. This difficulty, together with the interest in developing threedimensional SMAs devices for MEMS, has moved attention towards the use of compression tests on simple features like micro and nano pillars produced by focused ion beam machining.

Results and discussions In previous works, completely recoverable superelastic strain and shape memory in micro and

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jose.sanjuan@ehu.es , maria.no@ehu.es

nano pillars was first reported for Cu-Al-Ni SMAs [4] showing the competitive advantage of these SMAs over the commercially used of Ti-Ni. In addition several size effects on superelastic behaviour were also demonstrated [5-7] in Cu-AlNi SMAs. However, for practical applications the superelastic behavior must be reproducible over hundred or thousand of cycles, in order to be functionally reliable, and the first studies on cycling micropillars by nano compression tests were recently published [8].

In the present work a more complete study on long term cycling has been approached. In Figure 1 a micro pillar of 1.6 mm diameter milled by focused ion beam (FIB) on a [001] oriented single crystal of Cu-Al-Ni SMA is shown. In Figure 2 two consecutive nano compression superelastic cycles performed on the micropillar of Figure 1, by means of a nano-indenter are presented, as an example of the reproducibility of the superelastic behavior at this scale. The reproducibility is quite good, but in order to verify the reliability of such behavior with view to further applications, long-term cycling would be required. So, o perform a more complete study of the long term superelastic cycling, several arrays of micropillars have been milled in a FEI DualBeam Helios 650 FIB and systematically tested by nanocompression in a Hysitron TI 950 instrumented nanoindenter.

An excellent superelastic behavior with an extremely good reproducibility at the nano-scale has been observed up to more than 2000 nano compression tests. These arrays of micropillars and the experiments of long term superelastic cycling will be presented and on the light of these results, the potential interest of Cu-Al-Ni SMA for the development of smart MEMS, which are being called SMEMS, will be discussed

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Jose San Juan 1 J.F. Gómez-Cortés 2 G. A. López J. Chengge3 and 2 M. L. Nó

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Nano-scale Superelastic behavior of Shape Memory Alloys for potential MEMS applications

Conclusions Fully recoverable and reproducible superelastic behavior has been obtained during long term cycling tests above thousand cycles. These promising results open the door for designing potential applications doing use of 3D devices of SMA, which could be integrated in MEMS technology.

Figures

Acknowledgements: This work was supported by the Spanish MICINN project MAT2009-12492 and the Consolider-Ingenio 2010CSD2009-00013, by the Consolidated Research Group IT310-10 from the Education Department of the Basque Government and the project ACTIMAT from ETORTEK program of Industry Department of the Basque Government. JSJ and MLN also acknowledge support from EOARD through the grant FA8655-10-1-3074.

Figure 1: Micropillar of Cu-Al-Ni SMA milled by FIB on a [001] oriented single crystal, for nano-compression tests.

References

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[1] Kohl M., Shape Memory Microactuators.

(Springer-Verlag, Berlin, 2004).

[2] Humbeeck J. V., Shape Memory Alloys: A Material and a Technology. Adv. Eng. Mat. 3, 837 (2001).

[3] Miyazaki S, Fu YQ, Huang WM, Editors. Thin Film Shape Memory Alloys. (Cambridge University Press, Cambridge, 2009).

[4] San Juan J., Nรณ M.L. and Schuh C.A., Superelasticity and Shape Memory in Microand Nanometer-scale Pillars. Adv. Mater. 20, 272 (2008).

[5] San Juan J., Nรณ M.L. and Schuh C.A., Nanoscale shape-memory alloys for ultrahigh mechanical damping. Nature Nanotechnology 4, 415 (2009).

[6] San Juan J., Nรณ M.L. and Schuh C.A., Thermomechanical behavior at the nanoscale and size effects in shape memory alloys. J. Mater. Res. 26 (2011) 2461. (Invited feature paper).

[7] San Juan J., Nรณ M.L., Superelasticity and shape memory at the nano-scale: Size effects on the martensitic transformation. J. Alloys Compd.

(2011), doi:10.1016/j.jallcom.2011.10.110.

[8] San Juan J., Nรณ M.L. and Schuh C.A., Superelastic cycling of Cu-Al-Ni shape memory alloy micropillars. Acta Materialia 60, 4093 (2012).

Figure 2: Nano-compression cycling in the Cu-Al-Ni micro pillar of Figure 1, performed in a Hysitron TI-950 instrumented nanoindenter. Reproducible behavior, showing two consecutive cycles numbered as 112 & 113.

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Oral Joule-Thomson SPM for in situ sample analysis in extreme environments

Violeta Simic-Milosevic

violeta.simic-milosevic@specs.com SPECS Surface Nano Analysis GmbH Voltastrasse 5, 13355 Berlin, Germany

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and limits will be discussed. Finally applications and examples will be presented.

References

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[9] L. Zhang, T. Miyamachi, T. Tomanic, R. Dehm, and W. Wulfhekel, Rev. Sci. Instrum. 82 (2011) 103702.

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Due to miniaturization of modern devices down to the nanoscale the importance of knowledge and control of surface properties at this level is continuously increasing and necessary for the correct device operation. Often such devices are working at elevated or near ambient pressures of defined working gas mixtures, in liquid media, or electric potentials or magnetic fields have to be applied. Also extremely low or high temperatures might be necessary.

To contribute to advanced materials analysis and development in future means using scanning probe microscopy (SPM) and related techniques in highly demanding requirements as a key tool for nanotechnology. In UHV applications strong emphasis lies on the spectroscopic methods such as scanning tunneling spectroscopy and inelastic tunneling spectroscopy as well as single atom and molecule manipulation. For this kind of applications a system operating sample and sensors in thermal equilibrium at 1K and magnetic field up to 3T is a huge advantage over standard SPM instruments which do not work under these extreme environments. With the new JouleThomson SPM [1] working at 1K the thermal broadening of the Fermi edge is reduced significantly compared with what is typically observed at 4 K. As a result the resolution in spectroscopic measurements is increased significantly. The modular design allows for various experimental configurations and for the usage of different sensors as well as of the high magnetic field.

This work summarizes and presents existing solutions based on a combination of the JouleThomson cooling stage with extremely stable SPM heads. Future development routes to new instruments for materials analysis being functional under extreme working conditions, opportunities

Oral Understanding of the Size Control of Biocompatible Gold Nanoparticles in Millifluidic Channels: in situ SAXS/XANES/UV

Fabienne Testard 1 J. Han 1 F. Malloggi P. -E. Coulon2 3 N. Menguy and 1 O. Spalla

1

fabienne.testard@cea.fr 1

CEA, Saclay, DSM/IRAMIS/SIS2M/LIONS UMR 3299, 91191 Gif sur Yvette, France 2 LSI_Ecole Polytechnique, route de Saclay, 91128 Palaiseau cedex 3 IMPMC, UMR CNRS-Université Pierre et Marie Curie- Université Paris Diderot, 75005 Paris, France

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The high potentiality of applications of gold nanoparticles leads to the development of several synthetic roots for size and shape selection. If experimental strategies have been described to achieve such control, predictions in this field are still lacking when the nature of the reducing agent or the ligands are modified. In the particular case of the synthesis of gold nanoparticles in water with no added extra ligands [1] (very promising for biomedical applications), the control of the size and polydispersity is more difficult to obtain. A complete description of the underlying mechanism is mandatory to go towards more prediction in the control of size, shape and polydispersity. This project focuses on a mechanistic understanding of size controlled of biocompatible gold nanoparticles (GNP’s).

The control of the mixing of the reducing solution with the gold salt solution is certainly a key point to control the nucleation and growth steps and as a consequence the dispersion. Recently, microfluidics tools have been used to improve the mixing during nanoparticles synthesis with apparently a good way to access to a higher monodispersity [2,3]. In this context, we elucidated the size control of gold nanoparticles synthesized in surfactant free water [4] with a continuous flow mode also used to produce higher concentration (3 mM) of stabilized gold nanoparticles. The reaction between a reducing agent (ascorbic acid) and a gold (III) salt in water is very rapid (>1s). The originality of our approach was to finely modulate the initial pH of the reducing agent instead of the gold precursor to modify the kinetic of the reaction. The pH modification of the initial gold precursors Au(III) are stopped by the acceleration of their reduction into Au(0), ensuring the control of the final size (from 3 to 25 nm) of the gold nanoparticles with a

low polydispersity in size in aqueous surfactant free solution.

In situ SAXS/XANES/UV measurement with high time resolution (20 to 100 ms) have allowed the accurate measure of the size distribution of nanoparticles with the precise concentration of the different redox species during the reaction [6]. These experimental results were combined with the use of a model [5] based on the coupling of nucleation and growth equations together with a progressive injection of monomers. The main result is that the size of the particles is indeed controlled by the kinetic of reduction of gold atoms. As a consequence, the measure of the injection of monomers is the key to obtain prediction of the size of the final nanoparticles. At the end, we have shown that a millifluidic set-up equipped with a homemade mixer offers a robust way of rapid mixing to obtain a reproducible production of large amounts of nanoparticles.

References [1] Andreescu D., Sau T.K. and Goia D.V.J.; J. Colloid Interface Sci. 298 (2006), 742-751.

[2] Song Y., Hormes J. and Kumar C. S. S. R, Small, 4 (2008) 698-711.

[3] Luty-Blocho M., Fitzner K., Hessel V. , Löb P., Maskos M. , Metzke D., Paclawski K., Wojnicki M., Chem. Eng. J. 171 (2011), 279-290.

[4] Jun H., Testard F., Malloggi F., Coulon P-E., Menguy N., Spalla O., Langmuir, 28 (2012) 15966-15974.

[5] Abécassis B., Testard F., Kong Q., Baudelet F., Spalla O., Langmuir 26 (2010), 13847-13854.

[6] Jun H., Testard F,.Tache O., Spalla O., submitted.

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Figures

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Figure 1: A) SAXS patterns of GNPâ&#x20AC;&#x2122;s obtained with [Au(III)]i = 6mM, AA/Au(III) = 2, (red): pH = 10.6, (blue): pH=11.1 and (green): pH=11.8. B) HRTEM of representative gold nanoparticles obtained at pH=11.8. C) Size distribution from TEM analysis for red (pH=10.6) and blue (pH=11.1).

Oral Spin-helical transport in normal and superconducting topological insulator materials

Wuerzburg University, Am Hubland, 97074 Wuerzburg, Germany

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This work is focused on transport phenomena in topological insulators (TIs). Unlike conventional insulators, these novel nanomaterials (e.g. based on HgTe, Bi2Se3, Bi2Te3 etc.) exhibit nontrivial conduction properties originating from metalliclike edge or surface states. These boundary states are topologically protected and characterized by spin helicity whereby the direction of the electron spin is locked to the momentum direction. In this contribution, we demonstrate, both theoretically and experimentally, that the spin helicity leads to several unusual transport phenomena in HgTebased TIs: (i) Single-valley Dirac-fermion transport [1]. Using the band-structure calculations, we show that zerogap HgTe quantum wells possess a singlevalley Dirac-like dispersion [see Fig.1 (left)]. In a magnetic field, the system exhibits the quantum Hall effect with odd plateaus, characteristic of Dirac fermions [Fig. 1(middle)]. Also, the conductivity at the Dirac point (so called minimal conductivity) and its temperature dependence can be understood from the single-valley Dirac physics [Fig. 1(right)]. These results pave the way to study effects related to spin coherence of Dirac fermions. (ii) Weak anti-localization [2]. As well known, in low-dimensional conventional systems electronic states tend to be localized by static disorder (e.g. due to impurities). Remarkably, this never happens for helical carriers in TIs because of spin Berry phases that hinder contructive quantum interference in the random disorder potential [see Fig. 2 (left)]. Moreover, we find that HgTe-based TI materials exhibit weak anti-localization observable via a positive magnetoresistance effect [see Fig. 2 (right)].

Grigory Tkachov E. M. Hankiewicz H. Buhmann and L. W. Molenkamp

Grigory.Tkachov@physik.uniwuerzburg.de

(iii) Zero-bias anomaly [3] and topological midgap states in Josephson junctions [4]. We also investigate transport in HgTe TIs with superconducting contacts. We observe and theoretically explain a zero-bias anomaly (pronounced resistance drop) resulting from Andreev reflection and the induced superconductivity on the TI surface [Fig. 3].

Furthermore, we identify theoretically midgap Andreev bound states [Fig. 4] which are intimately related to topological Majorana states. These findings show that HgTe is a promising material to search for the signatures of the Majorana fermions in TI transport.

Acknowledgements: This work has been supported by the German Research Foundation (DFG) through Grants No. HA5893/3-1 and No. TK 60/1-1.

References [1] B. Buettner, C.X. Liu, G. Tkachov, E.G. Novik, C. Bruene, H. Buhmann, E.M. Hankiewicz, P. Recher, B. Trauzettel, S.C. Zhang, and L.W. Molenkamp, Single valley Dirac fermions in zero-gap HgTe quantum wells, Nature Phys. 7 (2011) 418.

[2] G. Tkachov and E. M. Hankiewicz, Weak antilocalization in HgTe quantum wells and topological surface states: Massive versus massless Dirac fermions, Phys. Rev. B 84 (2011) 035444.

[3] L. Maier, J.B. Oostinga, D. Knott, C. Bruene, P. Virtanen, G.Tkachov, E.M. Hankiewicz, C. Gould, H. Buhmann, and L. W. Molenkamp, Induced superconductivity in the three-

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dimensional topological insulator HgTe, Phys.

Rev. Lett. 109 (2012) 186806.

[4] G. Tkachov and E. M. Hankiewicz, Spin-helical transport in normal and superconducting topological insulators (Review Article), Phys.

Status Solidi B 250 (2013) 215.

Figures

Figure 1: (left) Theoretical single-valley Dirac-like dispersion of 2D HgTe system, (middle) measured Hall conductivity with predicted odd plateaus, and (right) temperature dependence of the conductivity at the Dirac point: circles – experiment, read line – theoretical fit based on quantum Kubo formula (from [1]).

Figure 3: (left) Measured differential resistance dV/dI versus bias V and magnetic field B, and (right) Theoretical Andreev reflection probability rA(E) versus energy E. Three maxima in the energy dependence rA(E) correspond exactly to the minima in the bias dependence dV/dI(V), as expected for proximity induced superconductivity (from [3]).

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Figure 2: (left) Schematic of interfering electron trajectories giving rise to weak anti-localization in disordered topological insulators.

Trajectories involve opposite spins σ and -σ as a result of Berry phase of π. (left) Magneticfield dependence of the WAL magnetoconductivity.

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Figure 4: Topological 4π-periodic Andreev bound states in a TI Josephson junction. At superconducting phase difference χ = π midgap Majorana states appear (from [4])

Invited High resolution XRF using capillary optics

CNRS, UMR7325,13288, Marseille, France Aix-Marseille Univ., CINaM, 13288, Marseille, France

272

Classical XRF measurements are commonly performed in synchrotron facilities because the technique requires a high brightness X-ray source.

Thanks to the development of polycapillary lens [1], sharply focusing X-ray beams on samples, the technique can now be performed in laboratory.

The lateral resolution is essentially linked to the incident beam geometry and is currently in the range of tens of micrometers. On the other hand, imaging chemical composition and structure at nanometer dimensions is a keypoint in nanoscience, especially for structures and properties characterization of embedded interface.

For this purpose, non-destructive techniques, based on X-ray irradiation have a leader place.

We have developed an experimental test-bed to estimate the ultimate resolution reachable by XRF. This equipment includes a microfocused X-ray low power source, and an EDX detector equipped with a cylindrical glass capillary, increasing the X-ray fluorescence collection yield. It is based on a confocal configuration since the detected signal comes from the intersect between the volume excited nearby the source lens focal plane and the analyzed volume in the aperture of the capillary.

The set-up was evaluated using test samples consisting in a molybdenum grid (250μm mesh) glued on an iron substrate. Significant XRF signal level with 50s acquisition time was recorded through a 25μm radius capillary for detection.

Spectra were recorded along a scan line crossing the grid. The spectroscopic signal shows good correlation between molybdenum Ka and iron Ka signals, as shown in figure 1. A similar grid was then used as a mask for thin titanium pattern evaporation on a cobalt sample. A 5 μm radius capillary was used to collect the sample X-ray fluorescence. The Cobalt Ka line is detected on the whole line scanned, since titanium is thin enough

Diddier Tonneau, M. Dehlinger S. Lavandier I. Ozerov F. Bedu and C. Fauquet didier.tonneau@univ-amu.fr

to allow the Co-Ka photons to escape. The titanium spectroscopic trace fits with the expected pattern.

The use of thin capillaries for XRF detection opens the way to 500 nm lateral resolution in lab and 50 nm using brighter sources such as synchrotron facilities. Furthermore, approaching the capillary extremity towards the surface in near field mechanical interaction would allow to image the surface topography simultaneously to sample chemical mapping. This concept has already been demonstrated in previous works [2, 3].

References [1] See for example: A. Bjeoumikhov, S. Bjeoumikhova, in Modern Developments in Xray and Neutron Optics, ed. By A. Erko, M. Idir, T. Krist, A. G. Michette, Springer Series in Optical Science, Vol. 137, p287-306 (2008).

[2] C. Fauquet, M. Dehlinger, F. Jandard, S. Ferrero, D. Pailharey, S. Larcheri, R. Graziola, J. Purans, A. Bjeoumikhov, A. Erko, I. Zizak, B. Dahmani and D. Tonneau, Nanoscale Research Letters 6 (2011), 308.

[3] Mapping of X-ray induced luminescence using a SNOM probe F. Jandard, C. Fauquet, M. Dehlinger, B. Dahmani, A. Bjeoumikhov, S. Ferrero, D. Pailharey, D. Tonneau, Appl. Surf.

Sci. Vol. 267 (2013), 81-85.

Figures

Figure 1: Fe (blue) and Mo (pink) signals recorded along a scan line on the sample.

ImagineNano2013

Invited Nanoscale effects at complex-oxide superconducting/ferroic hybrids 1

Unité Mixte de Physique CNRS/Thales, Palaiseau, France GFMC, Universidad Complutense de Madrid, Spain Université Paris Sud, Orsay, France

2 3

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1

A. Crassous1, C. Visani1 Z. Sefrioui2, R. Bernard1 S Fusil1, K. Bouzehouane1 J. Tornos2, C. León2 J. Briatico1, M. Bibes1 A. Barthélémy1,3 and J. Santamaría2

switch “on” and “off” high-temperature superconductivity. Furthermore, through this mechanism and owing to the ability to reversibly design the ferroelectric domain structure, we show that it is possible to produce a nanoscale modulation of the superconducting condensate [2].

This opens new possibilities for superconducting nano-electronic devices, which may exploit flux quantization [4,5] and Josephson coupling effects.

Another interesting possibility is to literally merge the most distinctive property of each of the constituents in order to observe truly hybridized behaviour. In the second part of the talk, we will show an example on how to unite the long-range phase-coherent charge transport characteristic of superconductivity and the spin-polarized charge transport characteristic of ferromagnetism, which may open the door to novel spintronic devices [6].

This is demonstrated in experiments with heterostructures that combine YBa2Cu3O7-x and the half-metallic ferromagnet La0.7Ca0.3MnO3. [7]

References [1] M. Bibes, J. E. Villegas and A. Barthélémy, Advances in Physics, 60 (2011) 5.

[2] A. Crassous, R. Bernard, S. Fusil, K. Bouzehouane, D. Le Bourdais, S. EnouzVedrenne, J. Briatico, M. Bibes, A. Barthélémy, and Javier E. Villegas, Phys. Rev. Lett. 107 (2011) 247002.

[3] A. Crassous, R. Bernard, S. Fusil, K. Bouzehouan, J. Briatico, M. Bibes, A. Barthélémy, and Javier E. Villegas, Jour. Appl.

Phys. 113 (2013) 024910.

NANOSPAIN 2013

javier.villegas@thalesgroup.com

273

The physical properties of hybrid structures in which dissimilar materials are combined may radically differ from those of the individual constituents, as novel sometimes unexpected behaviors arise due to competing interactions. The latter are enhanced by the reduced dimensionality, the confinement, and the intimate (nanoscale) contact at the interfaces. Interestingly, external stimuli having moderate effects on each of the constituents may on the contrary induce dramatic effects in the hybrid structure, as they break a delicate balance resulting from the interface interactions. This allows engineering artificial materials with new functionalities. Oxide perovskites offer much potential for this, due to the large variety of isostructural materials available which exhibit different ground states (high-Tc superconductors, insulators, ferroics), and owing to the possibility of combining them in highquality heterostructures [1].

One interesting possibility is to couple one of the constituents’ sensitivity to external stimuli (e.g. electric or magnetic fields) to a measurable, strongly varying physical property of the other constituent (e.g. the electrical resistance in a superconductor). We will show an example of this in the first part of the talk. We exploit the possibility for oxide superconductors of varying the superconducting critical temperature under the application of an electrostatic field. This effect is produced here in heterostructures that combine a large-polarization ferroelectric (BiFeO3) and a hightemperature superconductor (YBa2Cu3O7-x). We demonstrate that this particular system allows for an unusually large modulation of the critical temperature upon reversal of the ferroelectric polarization by the momentary application of an electric field [2,3]. This enables one to effectively

Javier E. Villegas

274

[4] I. Swiecicki, C. Ulysse, T. Wolf, R. Bernard, N. Bergeal, J. Briatico, G. Faini, J. Lesueur and J. E. Villegas, Phys. Rev. B 85 (2012) 224502.

[5] J. E. Villegas, et al. Nanotechnology 22 (2011) 075302.

[6] M. Eschrig, Phys. Today 64, 43 (2011).

[7] C. Visani, Z. Sefrioui, J. Tornos, C. León, J. Briatico, M. Bibes, A. Barthélémy, J. Santamaría and Javier E. Villegas, Nature Physics 8 (2012) 539.

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Invited Exploring Magnetism in the Nanoworld

Roland Wiesendanger

Institute of Applied Physics and Interdisciplinary Nanoscience Center Hamburg, University of Hamburg, D-20355 Hamburg, Germany

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References

NANOSPAIN 2013

[1] R. Wiesendanger, Rev. Mod. Phys. 81, 1495 (2009).

[2] F. Meier et al., Science 320, 82 (2008).

[3] L. Zhou et al., Nature Physics 6, 187 (2010).

[4] A. A. Khajetoorians et al., Nature Physics 8, 497 (2012).

[5] A. A. Khajetoorians et al., Science 332, 1062 (2011).

[6] S. Heinze et al., Nature Physics 7, 713 (2011).

275

The developments of novel magnetic materials as well as spin-based electronics are hot topics of current research in nanoscale science. Both research fields profit tremendously from atomicscale insight into magnetic properties and spindependent interactions at the atomic level. Based on the development of spin-polarized scanning tunneling microscopy (SP-STM) [1] we have recently established the novel method of singleatom magnetometry [2,3] which allows the measurement of magnetization curves and the determination of magnetic moments on an atomby-atom basis. While the sensitivity level of singleatom magnetometry is below one Bohr magneton, it can easily be combined with the atomicresolution imaging and manipulation capabilities of conventional STM, thereby offering a novel approach towards a rational material design based on the knowledge of the atomic-level properties and interactions within the solid state [4].

Moreover, an atom-by-atom design and realization of all-spin logic devices [5] has recently been demonstrated by our group based on the combined knowledge derived from surface physics, nanoscience, and magnetism.

By using SP-STM we have recently discovered nanoskyrmion lattices of single atomic layers of transition metals on particular substrates exhibiting a large spin-orbit coupling. In this case, skyrmionic lattices can be stabilized by Dzyaloshinskii-Moriya interactions combined with the breaking of inversion symmetry at surfaces and interfaces [6]. Following this approach, the existence of skyrmions of ultimate small size, being stable even in zero field, has recently been demonstrated, offering great potential for future nanospintronic devices.

wiesendanger@physnet.unihamburg.de

Oral Ratchets: from driven and noisy to stationary and deterministic optical ratchets

Ivar Zapata Olson-Lunde

Depto. Física de la Materia Condensada C-3 Instituto Nicolás Cabrera, despacho 01.08.DE.401-2 c/ Francisco Tomás y Valiente, 7. Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco. 28049 Madrid, Spain

276

A ratchet effect occurs when an unbiased external medium (having here the restricted meaning of zero spatial and temporal averaging of external forces) is nonetheless able to induce motion in a preferred direction. Hence, the system can overcome a small bias against the preferred direction of motion: these systems are remarkable rectifiers, and the number of their applications is overwhelming. In 1D, most ratchets fall under the general (non-exclusive) categories of pulsating or tilting ratchets. On the other hand, in 2D there are forces which don’t derive from a potential, and hence a stationary (non-driven) and purely deterministic ratchet is allowed. An example is shown which makes use of optical vortices.

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Oral A Culinary Herb Extract to Synthesize Silver Nanoparticles

Araceli Zavaleta-Mancera

1

L.M. Carrillo-López1 A.R. Vilchis-Néstor2 R.M. Soto-Hernández1 J.Arenas-Alatorre3 L. Trejo-Téllez1 and F. Gómez-Merino1

1

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and the widening proportionally, specifically for particles above 10 nm diameter, leading to higher light dispersion [3]. Particle characterization, to examine the size and shape of the particles as well as the crystal structure, was performed using transmission electron microscopy (Jeol 2010 TEM) operating at 200 kV and selected area electron diffraction (SAED) at the Research Center of Sustainable Chemistry, UAEM-UNAM. Figure 3 shows a representative micrograph of the formed silver nanoparticles after 15 d of reaction, with 1 mL of extract. The particle size distribution indicated that average size was 14.9 ± 7.5 nm although the greater population was between 5-10 nm (Figure 4). The SAED pattern indicated that it was a polycrystalline sample (insert, Figure 3). The diffraction rings of inside out can be indexed with the planes (111), (200), (220), (311) and (420), respectively, which correspond to the structure facecentered cubic (fcc) of the silver (JCPDS 04 0784). The nanoparticles obtained with this system were stable for more than eight months at 20 °C. Acknowledgements: This research was partially supported by the Línea Prioritaria de Investigación LPI-16 “Innovación Tecnológica” of the Colegio de Postgraduados and it is also part of the Doctor in Science research of the first author, granted by CONACYT-México.

References [1] N.K. Badri and N. Sakthivel. Material Letters 62 (2008) 4588-4590.

[2] S.P. Chandran, M. Chaudhary, R. Pasricha, A. Ahmad and M. Sastry. Biotechnology Progress 22 (2006) 577-583.

277

The biosynthesis of nanoparticles with plant extracts or in whole plants is a promising technique which produces particles of attractive shapes, homogeneous in composition and sizes, in an organic and friendly environment. It has been reported the biosynthesis of Au nanoparticles by plants like alfalfa, Aloe vera, Cinnamomum camphora, neem, Emblica officianalis, lemongrass (Cymbopogon flexuosus) and tamarind (Tamarindus indica); however the potential of plants as biological material for the synthesis of nanoparticles has not been fully explored [1]. The aim of this research is to evaluate the potential of aqueous extracts of the Mexican culinary herb (Chenopodium ambrosoides L.) in the biosynthesis of Ag nanoparticles using AgNO3 as precursor. For in vitro biosynthesis, the extracts were prepared according to Chandran [2]. Six volumes (0.1, 0.2, 0.5, 1, 2, 3 and 5 mL) of extract and two concentrations (10-2 and 10-3 M) of AgNO3 were tested. Formation of nanoparticles was monitored periodically by UV-Vis spectrophotometry (Perkin Elmer Lambda 40 spectrophotometer UV/VIS). The aqueous extracts developed a yellow color, associated with the formation of silver nanoparticles. The presence of nanoparticles was corroborated by the presence of the surface plasmon resonance (SPR) at 438 nm. Increases in quantity extract increases particle size, but the concentration of silver nitrate showed an inverse ratio. In most of ours studied systems the shapes of the obtained particles were considered quasispherical.

The intensity of the absorption at 438 nm in the UV-Vis spectra increases with time, reaching a stable value after 15 d of reaction (Figure 2).

Increases in volume extracts promoted displacement of the maximum absorption band

luismanuel@colpos.mx arazavaleta@colpos.mx

NANOSPAIN 2013

Colegio de Postgraduados. Km. 36.5 Carr. México-Texcoco, 56230. Texcoco, Edo. Mex. México 2 Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM. Km 14.5 Carr. Toluca - Atlacomulco, 50200 Estado de México, México 3 3Universidad Nacional Autónoma de México. Instituto de Física, Circuito de la Investigación SN, Ciudad Universitaria, 04510. Ciudad de México, DF, México

[3] A. Rico, A. R. Vilchis, V. Sﾃ｡nchez, M. ﾃ」alos and M.A. Camacho. Superficies y Vacﾃｭo 23 (2010) 94-97.

Figures

Figure 1: Characteristic coloration of silver nanoparticles obtained -2 with differen volumes of extract of C. ambrosioides and 10 M AgNO3. From left to right: 0.1, 0.2, 0.5, 1, 2, 3 y 5 mL of extract.

Figure 2: UV-Vis spectyra of silver nanoparticles obtained with 5 mL of extract of C. ambrosioides and 10-2 M AgNO3 at different times.

Figure 3: Representative TEM micrograph of silver nanopartivles synthesized from 1 mL of extract of C. ambrosioides and 10-2 M AgNO3. The insert corresponds to the electron diffraction pattern of a face-centered cubic (fcc) structure.

278

Figure 4: Dispersion of silver nanoparticles sizes synthesized from 5 mL of C. ambrosioides and 10-2 M AgNO3

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nanoBioMed

2013

Index nanoBioMed2013 Contributions Invited

Pag

■ François Berger (Clinatech, Grenoble, France) Abstrat not provided by the speaker

-

■ Christophe Bernard (INS, INSERM UMR 1106, France) "In vivo recordings of brain activity using organic transistors"

300

■ Yves Dufrene (Univ. Catholique de Louvain, Belgium) "Force nanoscopy of microbial pathogens"

312

■ Paulo Freitas (INL, Portugal) "Challenges in spintronic platforms for biomedical applications"

316

■ Neil Gibson (Joint Research Centre, Italy) "Radiolabelling of Nanoparticles using Cyclotron-Based Techniques"

325

■ Jesper Glückstad (DTU Fotonik, Denmark) "New two-photon based nanoscopic modalities and optogenetic"

326

■ Gabriel Gomila (IBEC, Spain) "Dielectric properties of biological samples measured at the nanoscale: from single bacteria to single viruses"

327

■ Uzi Landman (Georgia Inst. of Tech., USA) Abstrat not provided by the speaker

-

■ Sébastien Lecommandoux (LCPO- UMR 5629, Bordeaux, France) "Biomimetic polypeptide and polysaccharide based polymersomes for therapy and diagnosis"

332

■ Luis Liz-Marzán (CIC biomaGUNE, Spain) "Biosensing with Gold Nanoparticles"

335

■ Gustavo S. Luengo (L'Oréal Recherche, France) "Skin applications of Atomic Force Microscopy"

336

■ Tomonobu Nakayama (NIMS, Japan) "Multiple-probe scanning probe microscopy: a potential application to bio-inspired materials research"

342

■ Niels Chr. Nielsen (iNANO / University of Aarhus, Denmark) "Structural characterization and mimicking of biological nanostructures in native heterogeneous environment"

343

■ Peter R. Ogilby (Aarhus University, Denmark) "Singlet Oxygen in Mammalian Cells: Exploiting Nanoscopic Tools in Single"

346

■ Valery Pavlov (CIC biomaGUNE, Spain) "Enzymes and fluorescent nanoparticles"

347

■ Raul Perez-Jimenez (CIC nanoGUNE, Spain) "Molecular nanomechanics in human health"

349

■ Victor Puntes (ICN, Spain)

ImagineNano2013

353

281

"Detoxifying Antitumoral Drugs via Nanoconjugation: The Case of Gold Nanoparticles and Cisplatin"

Invited

Pag

■ Sebastian Schluecker (Univ. of Duisburg-Essen, Germany) "SERS Microscopy: Tissue Diagnostics with Rationally Designed Nanoparticle Probes"

365

■ Rupert Tscheliessnig (Austrian Center for Industrial Biotechnology, Austria) 371

"Visulaization of proteins in solution - in situ"

■ Mark Welland (University of Cambridge, UK) -

Abstrat not provided by the speaker

■ Horst Weller (Universität Hamburg, Germany) 380

"Precisions synthesis of nanocrystals and their use in biomedical applications"

■ Claire Wihelm (CNRS and Université Paris Diderot, France) "Biomedical applications of magnetic nanoparticles: from cell imaging to tissue engineering"

Oral

381

Pag

■ Achraf Al Faraj (King Saud University, Saudi Arabia) "Preferential magnetic labeling and in vivo tracking of bone marrow derived macrophages after their intravenous administration in COPD animal model"

291

■ Hisham Alhadlaq (King Saud University, Saudi Arabia) 293

"Anticancer Activity of Engineered Nanomaterials"

■ Lamiaa M.A Ali (Instituto de Ciencia de Materiales de Aragon (ICMA, Spain) Biodistribution studies of polymer coated superparamagnetic iron oxide nanoparticles using Magnetic Resonance Imaging"

294

■ Prabhuraj Balakrishnan (University of Manchester, United Kingdom) "Voltammetric glucose sensor using poly(2,5 dimethoxy aniline) as a polymer support"

296

■ Sheila Becerro Martínez (CIC Microgune, Spain) "Interdigitated biosensor for multiparametric monitoring of bacterial biofilm development"

298

■ Cristina Bertulli (University of Cambridge, United Kingdom) "Spectroscopic Characterization of Protein-Wrapped Single-Wall Carbon Nanotubes and Quantification of Their Uptake in Macrophages"

301

■ Arkady Bitler (Weizmann Institute of Science, Israel) "Geometrical and mechanical fine structure of peptidoglycans in living Streptococcus bacteria studied by AFM nanomechanical mapping"

303

■ Alessandro Bosco (Elettra - Sincrotrone Trieste S.C.p.A., Italy) "ELISA - like nano-immuno assay for the proteomic analysis of malignant gliomas"

304

■ Jonathan Bruniaux (CEA, France) 305

"Multifunctional lipid nanoparticles dedicated to RNAi screening"

■ Wei-Hung Chen (National Chung-Hsing University, Taiwan) 307

"Label-free Gold Nanoparticle Biosensor for alpha-fetoprotein Detection"

■ Enav Corem Salkmon (Bar-Ilan University, Israel) "Design of near-infrared fluorescent bioactive conjugated functional iron oxide nanoparticles for optical

282

detection of colon cancer"

308

ImagineNano2013

Oral

Pag

■ Carme de Haro (Fundacion CETEMMSA, Spain) "Development of Hydrogel membranes for long term Biopotential monitoring"

310

■ Damien Dupin (IK4-CIDETEC, Spain) "Metallophilic Hydrogels: A New Family of Injectable and Self-Healing Materials"

313

■ Giancarlo Franzese (Universitat de Barcelona, Spain) "Nanoassembly of the Protein Corona on Nanoparticles"

315

■ Gaizka Garai Ibabe (CICbiomaGUNE, Spain) "Application of the enzymatic product-mediated stabilization of in situ produced CdS quantum dots: serum paraoxonase, acetylcholine esterase"

318

■ Jose V Garcia-Ramos (Instituto de Estructura de la Materia. IEM-CSIC, Spain) "Detection of Alzheimer Disease Markers by High Performance Plasmonic Silver Nanostars"

320

■ Jan Gertenbach (PANalytical B.V., Netherlands) "Multi-purpose X-ray diffractometer platform with versatile SAXS/WAXS options"

322

■ Zahra Gholamvand (Dublin City University, Ireland) "Design of an efficient Graphene-based TiO2 nano-composite for photocatalytic removal of pharmaceuticals from water"

323

■ Sonja Hartl (BioNanoNet Forschungesellschaft mbH, Austria) "Safety Implementation of Nanotechnology for Chemical Enterprises within a Bottom-Up Approach towards Communication"

328

■ Clemens Helmbrecht (Particle Metrix GmbH, Germany) "Automated particle tracking (APT) for simultaneous zeta potential-, size distribution and concentration analysis of exosomes"

329

■ Wawrzyniec Kaszub (Universite de Rennes 1, France) "Ultrafast laser spectroscopy of molecular tweezers"

331

■ Kaisa Lilja (Biolin Scientific, Finland) "Cyclic measurements of DPPC monolayers at low surface tensions"

334

■ Maria Ada Malvindi (Istituto Italiano Di Tecnologia, Italy) "Silica nanostructures toxicity assessment and their potential for biomedical applications"

337

■ Lluis Marsal (Universitat Rovira i Virgili, Spain) "Functionalization of silicon dioxide micropillars for biosensing and microarray technology"

339

■ Ludovic Mayer (Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, France) "KTP nanocrystals exhibiting high SHG emission for bio-imaging applications"

341

■ Fernando Novio (Centro de Investigación en Nanociencia y Nanotecnología (CIN2-CSIC), Spain) "Multifunctional Coordination Polymer Particles for Bio-medical application"

344

■ Rafael Piñol (Instituto de Ciencia de Materiales de Aragón. CSIC-Universidad de Zaragoza, Spain) "Multifunctional Nanoplatform for Biomedical Applications"

350

■ Fernando Ponz (INIA, Spain) "Nanoparticles of plant origin exploited for multiple applications"

352

■ Hubert Ranchon (LAAS-CNRS, France)

ImagineNano2013

354

283

"Nanofluidic system for matrix-free DNA analysis"

Oral

Pag

■ Jessica Rodríguez-Fernández (Ludwig-Maximilians-Universität, Germany) "Towards DNA-Coated Anisotropic Building-Blocks: A Robust Surface Modification Strategy to Functionalize Gold Nanorods with DNA Oligonucleotides"

356

■ Roberto Rosal (IMDEA Agua, Spain) "Transformation and toxicity of PAMAM dendrimers under irradiation and ozonation processes"

357

■ Daniel Ruiz-Molina (CSIC, Spain) "Versatile Bionanostructured Materials via Direct Reaction of Functionalized Catechols"

359

■ Rosario M. Sanchez-Martin (University of Granada, Spain) "Recent therapeutic advances using polystyrene microspheres as delivery systems"

361

■ Thomas Schäfer (POLYMAT, Spain) 363

"Stimuli-Responsive DNA- Nanovalves for Controlled Delivery and Nanodevices"

■ Blanca Suarez-Merino (Fundacion GAIKER, Spain) "Current research strategies for toxicity assessment of engineered nanomaterials. Lessons learned from European Projects"

366

■ Sofia Teixeira (Swansea University, United Kingdom) 367

"Graphene Biosensor for Detection of hCG Biomarker"

■ Yanis Toledano (UNAM, Mexico) 369

"Biocompatibility of nanoclays for future applications in biomedicine"

■ Rodica Paula Turcu (National Institute R&D for Isotopic and Molecular Technologies, Romania) "Magnetoresponsive hybrid microgels: close packed magnetite nanoparticles core - double layer polymeric shells with anionic or cationic functionalities"

373

■ Barbara Unterauer (Profactor GmbH, Austria) 375

"Characterization of Functionalized, Magnetic Nanoparticles"

■ Ruben Van Roosbroeck (IMEC, Belgium) 376

"Synthetic Antiferromagnetic Nanoparticles As Contrast Agents In MRI"

■ Ladislau Vekas (Romanian Academy, Romania) "Hydrophobic and hydrophilic magnetite nanoparticles: non-polar and polar magnetic nanofluids designed for magnetic carriers manufacturing"

378

■ Malgorzata Wojtoniszak (West Pomeranian University of Technology in Szczecin, Poland) "Graphene/graphene oxide – multifunctional platform for drug delivery and photodynamic therapy in cancer treatment"

383

■ Alexey Yashchenok (Max-Planck Institute of Colloids and Interfaces, Germany) "Layer-by-Layer assembly of nanocomposite colloidal probes for Raman-based detection of biomolecules"

385

■ Tatiana Zimina (Saint Petersburg Electrotechnical University "LETI" (ETU), Russia) "In vitro diagnostics of microbial cells and their antibiotic resistance using nanostructured anodic aluminum

284

oxide growth platforms"

387

ImagineNano2013

Index nanoBioMed2013 Contributions Alphabetical Order I:Invited / O: Oral

Pag

■ Achraf Al Faraj (King Saud University, Saudi Arabia) "Preferential magnetic labeling and in vivo tracking of bone marrow derived macrophages after their intravenous administration in COPD animal model"

O

291

O

293

O

294

O

296

O

298

I

-

I

300

O

301

O

303

O

304

O

305

O

307

O

308

O

310

I

312

O

313

■ Hisham Alhadlaq (King Saud University, Saudi Arabia) "Anticancer Activity of Engineered Nanomaterials"

■ Lamiaa M.A Ali (Instituto de Ciencia de Materiales de Aragon (ICMA, Spain) Biodistribution studies of polymer coated superparamagnetic iron oxide nanoparticles using Magnetic Resonance Imaging"

■ Prabhuraj Balakrishnan (University of Manchester, United Kingdom) "Voltammetric glucose sensor using poly(2,5 dimethoxy aniline) as a polymer support"

■ Sheila Becerro Martínez (CIC Microgune, Spain) "Interdigitated biosensor for multiparametric monitoring of bacterial biofilm development"

■ François Berger (Clinatech, Grenoble, France) Abstrat not provided by the speaker

■ Christophe Bernard (INS, INSERM UMR 1106, France) "In vivo recordings of brain activity using organic transistors"

■ Cristina Bertulli (University of Cambridge, United Kingdom) "Spectroscopic Characterization of Protein-Wrapped Single-Wall Carbon Nanotubes and Quantification of Their Uptake in Macrophages"

■ Arkady Bitler (Weizmann Institute of Science, Israel) "Geometrical and mechanical fine structure of peptidoglycans in living Streptococcus bacteria studied by AFM nanomechanical mapping"

■ Alessandro Bosco (Elettra - Sincrotrone Trieste S.C.p.A., Italy) "ELISA - like nano-immuno assay for the proteomic analysis of malignant gliomas"

■ Jonathan Bruniaux (CEA, France) "Multifunctional lipid nanoparticles dedicated to RNAi screening"

■ Wei-Hung Chen (National Chung-Hsing University, Taiwan) "Label-free Gold Nanoparticle Biosensor for alpha-fetoprotein Detection"

■ Enav Corem Salkmon (Bar-Ilan University, Israel) "Design of near-infrared fluorescent bioactive conjugated functional iron oxide nanoparticles for optical detection of colon cancer"

■ Carme de Haro (Fundacion CETEMMSA, Spain) "Development of Hydrogel membranes for long term Biopotential monitoring"

■ Yves Dufrene (Univ. Catholique de Louvain, Belgium) "Force nanoscopy of microbial pathogens" "Metallophilic Hydrogels: A New Family of Injectable and Self-Healing Materials"

ImagineNano2013

285

■ Damien Dupin (IK4-CIDETEC, Spain)

I:Invited / O: Oral

Pag

■ Giancarlo Franzese (Universitat de Barcelona, Spain) "Nanoassembly of the Protein Corona on Nanoparticles"

O

315

I

316

O

318

O

320

O

322

O

323

I

325

I

326

I

327

O

328

O

329

O

331

I

-

I

332

O

334

I

335

I

336

O

337

O

339

■ Paulo Freitas (INL, Portugal) "Challenges in spintronic platforms for biomedical applications"

■ Gaizka Garai Ibabe (CICbiomaGUNE, Spain) "Application of the enzymatic product-mediated stabilization of in situ produced CdS quantum dots: serum paraoxonase, acetylcholine esterase"

■ Jose V Garcia-Ramos (Instituto de Estructura de la Materia. IEM-CSIC, Spain) "Detection of Alzheimer Disease Markers by High Performance Plasmonic Silver Nanostars"

■ Jan Gertenbach (PANalytical B.V., Netherlands) "Multi-purpose X-ray diffractometer platform with versatile SAXS/WAXS options"

■ Zahra Gholamvand (Dublin City University, Ireland) "Design of an efficient Graphene-based TiO2 nano-composite for photocatalytic removal of pharmaceuticals from water"

■ Neil Gibson (Joint Research Centre, Italy) "Radiolabelling of Nanoparticles using Cyclotron-Based Techniques"

■ Jesper Glückstad (DTU Fotonik, Denmark) "New two-photon based nanoscopic modalities and optogenetic"

■ Gabriel Gomila (IBEC, Spain) "Dielectric properties of biological samples measured at the nanoscale: from single bacteria to single viruses"

■ Sonja Hartl (BioNanoNet Forschungesellschaft mbH, Austria) "Safety Implementation of Nanotechnology for Chemical Enterprises within a Bottom-Up Approach towards Communication"

■ Clemens Helmbrecht (Particle Metrix GmbH, Germany) "Automated particle tracking (APT) for simultaneous zeta potential-, size distribution and concentration analysis of exosomes"

■ Wawrzyniec Kaszub (Universite de Rennes 1, France) "Ultrafast laser spectroscopy of molecular tweezers"

■ Uzi Landman (Georgia Inst. of Tech., USA) Abstrat not provided by the speaker

■ Sébastien Lecommandoux (LCPO- UMR 5629, Bordeaux, France) "Biomimetic polypeptide and polysaccharide based polymersomes for therapy and diagnosis"

■ Kaisa Lilja (Biolin Scientific, Finland) "Cyclic measurements of DPPC monolayers at low surface tensions"

■ Luis Liz-Marzán (CIC biomaGUNE, Spain) "Biosensing with Gold Nanoparticles"

■ Gustavo S. Luengo (L'Oréal Recherche, France) "Skin applications of Atomic Force Microscopy"

■ Maria Ada Malvindi (Istituto Italiano Di Tecnologia, Italy) "Silica nanostructures toxicity assessment and their potential for biomedical applications"

■ Lluis Marsal (Universitat Rovira i Virgili, Spain)

286

"Functionalization of silicon dioxide micropillars for biosensing and microarray technology"

ImagineNano2013

I:Invited / O: Oral

Pag

■ Ludovic Mayer (Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, France) "KTP nanocrystals exhibiting high SHG emission for bio-imaging applications"

O

341

I

342

I

343

O

344

I

346

I

347

I

349

O

350

O

352

I

353

O

354

O

356

O

357

O

359

O

361

O

363

I

365

O

366

O

367

O

369

I

371

■ Tomonobu Nakayama (NIMS, Japan) "Multiple-probe scanning probe microscopy: a potential application to bio-inspired materials research"

■ Niels Chr. Nielsen (iNANO / University of Aarhus, Denmark) "Structural characterization and mimicking of biological nanostructures in native heterogeneous environment"

■ Fernando Novio (Centro de Investigación en Nanociencia y Nanotecnología (CIN2-CSIC), Spain) "Multifunctional Coordination Polymer Particles for Bio-medical application"

■ Peter R. Ogilby (Aarhus University, Denmark) "Singlet Oxygen in Mammalian Cells: Exploiting Nanoscopic Tools in Single"

■ Valery Pavlov (CIC biomaGUNE, Spain) "Enzymes and fluorescent nanoparticles"

■ Raul Perez-Jimenez (CIC nanoGUNE, Spain) "Molecular nanomechanics in human health"

■ Rafael Piñol (Instituto de Ciencia de Materiales de Aragón. CSIC-Universidad de Zaragoza, Spain) "Multifunctional Nanoplatform for Biomedical Applications"

■ Fernando Ponz (INIA, Spain) "Nanoparticles of plant origin exploited for multiple applications"

■ Victor Puntes (ICN, Spain) "Detoxifying Antitumoral Drugs via Nanoconjugation: The Case of Gold Nanoparticles and Cisplatin"

■ Hubert Ranchon (LAAS-CNRS, France) "Nanofluidic system for matrix-free DNA analysis"

■ Jessica Rodríguez-Fernández (Ludwig-Maximilians-Universität, Germany) "Towards DNA-Coated Anisotropic Building-Blocks: A Robust Surface Modification Strategy to Functionalize Gold Nanorods with DNA Oligonucleotides"

■ Roberto Rosal (IMDEA Agua, Spain) "Transformation and toxicity of PAMAM dendrimers under irradiation and ozonation processes"

■ Daniel Ruiz-Molina (CSIC, Spain) "Versatile Bionanostructured Materials via Direct Reaction of Functionalized Catechols"

■ Rosario M. Sanchez-Martin (University of Granada, Spain) "Recent therapeutic advances using polystyrene microspheres as delivery systems"

■ Thomas Schäfer (POLYMAT, Spain) "Stimuli-Responsive DNA- Nanovalves for Controlled Delivery and Nanodevices"

■ Sebastian Schluecker (Univ. of Duisburg-Essen, Germany) "SERS Microscopy: Tissue Diagnostics with Rationally Designed Nanoparticle Probes"

■ Blanca Suarez-Merino (Fundacion GAIKER, Spain) "Current research strategies for toxicity assessment of engineered nanomaterials. Lessons learned from European Projects"

■ Sofia Teixeira (Swansea University, United Kingdom) "Graphene Biosensor for Detection of hCG Biomarker"

■ Yanis Toledano (UNAM, Mexico) "Biocompatibility of nanoclays for future applications in biomedicine" "Visulaization of proteins in solution - in situ"

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■ Rupert Tscheliessnig (Austrian Center for Industrial Biotechnology, Austria)

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■ Rodica Paula Turcu (National Institute R&D for Isotopic and Molecular Technologies, Romania) "Magnetoresponsive hybrid microgels: close packed magnetite nanoparticles core - double layer polymeric shells with anionic or cationic functionalities"

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■ Barbara Unterauer (Profactor GmbH, Austria) "Characterization of Functionalized, Magnetic Nanoparticles"

■ Ruben Van Roosbroeck (IMEC, Belgium) "Synthetic Antiferromagnetic Nanoparticles As Contrast Agents In MRI"

■ Ladislau Vekas (Romanian Academy, Romania) "Hydrophobic and hydrophilic magnetite nanoparticles: non-polar and polar magnetic nanofluids designed for magnetic carriers manufacturing"

■ Mark Welland (University of Cambridge, UK) Abstrat not provided by the speaker

■ Horst Weller (Universität Hamburg, Germany) "Precisions synthesis of nanocrystals and their use in biomedical applications"

■ Claire Wihelm (CNRS and Université Paris Diderot, France) "Biomedical applications of magnetic nanoparticles: from cell imaging to tissue engineering"

■ Malgorzata Wojtoniszak (West Pomeranian University of Technology in Szczecin, Poland) "Graphene/graphene oxide – multifunctional platform for drug delivery and photodynamic therapy in cancer treatment"

■ Alexey Yashchenok (Max-Planck Institute of Colloids and Interfaces, Germany) "Layer-by-Layer assembly of nanocomposite colloidal probes for Raman-based detection of biomolecules"

■ Tatiana Zimina (Saint Petersburg Electrotechnical University "LETI" (ETU), Russia) "In vitro diagnostics of microbial cells and their antibiotic resistance using nanostructured anodic

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aluminum oxide growth platforms"

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A b s t r a ct s Alphabetical order

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Oral Preferential magnetic labeling and in vivo tracking of bone marrow derived macrophages after their intravenous administration in COPD animal model

Achraf Al Faraj A. fzal Pasha Sheik and R. abih Halwani

aalfaraj@ksu.edu.sa

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M2 labeling efficiency was determined using two independent techniques: Ferrozine-based spectrophotometry and magnetophoresis (or Cell Tracking Velocimetry) assays.

Interestingly, both techniques showed statistically similar iron concentration in all labeled cells as the used magnetic nanoparticles have equal magnetization value. A higher uptake by M2 macrophages compared to M1 subsets was observed for all the different SPIO nanoparticles (Figure1a), which is in line with their role as debris scavengers. An enhanced labeling efficiency for both carboxylic and amine modified PEGylated SPIO was measured for M1 and M2 BMDM subpopulations. Along with their polarization flexibility, this will certainly pave the way for easier coupling of positively or negatively charged magnetic nanoparticles with specific antibody targeted to a particular subpopulation of macrophage and offer a promising strategy for an early and better diagnosis of inflammatory diseases using noninvasive MRI. Magnetic nanoparticles biocompatibility was then evaluated using MTT cell growth assay for cell viability, JC-1 fluorescence kit for mitochondrial membrane potential as a hallmark of apoptosis and 2’,7’ dichlorofluorescein diacetate (DCFDA) fluorogenic dye for Reactive oxygen species generation. No variation in cell viability and mitochondrial membrane potential was detected after labeling M1 and M2 macrophages with the different magnetic nanoparticles (Figure1b), which confirms the safety of the used dextran-coated SPIO nanoparticles and their further surface modifications. However, a statistically significant increase in ROS generation was measured mainly with plain SPIO nanoparticles and to a lower extent with carboxylic and amine modified PEGylated

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Noninvasive imaging of macrophages activity has raised increasing interest for diagnosis of different diseases, which make them attractive vehicles to deliver contrast agents for diagnostic or drugs for therapeutic purposes. Coupled with the use of super-paramagnetic iron oxide (SPIO) nanoparticles, MR Imaging of macrophages offers a promising noninvasive approach for an early and better assessment of the pathological and physiological impairments in chronic obstructive respiratory diseases (COPD). However, before developing such targeted delivery mechanism, the effect of their magnetic labeling need further investigation. Inside the body, different environmental conditions will orient macrophages to have either a pro-inflammatory (M1) or immuno-modulator (M2) profile. In this study, the effect of SPIO PEGylation (addition of Polyethylene Glycol) and their further surface modification with carboxylic (-COOH) or amine (-NH2) groups on M1 and M2 bone marrow derived macrophages (BMDM) phenotype, labeling efficiency and toxicity was first investigated. Then, macrophages biodistribution and noninvasive tracking were assessed after their intravenous administration in a COPD animal model.

Bone marrow cells issued from tibiae and femora of donor Balb/c mice were first differentiated into M1 or M2 polarized macrophages [1]. They were then labeled with either SPIO, SPIO-PEG, SPIO-PEGCOOH or SPIO-PEG-NH2 nanoparticles (100 nm) at extracellular iron concentration of 2 mM (100 μg/ml). Labeling conditions (i.e., nanoparticles size and concentration, incubation time, culture medium …) were based on preliminary study performed on non-polarized macrophages labeled with SPIO showing a best compromise between labeling efficiency and biocompatibility [2]. M1 and

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King Saud University, College of Applied Medical Sciences, Riyadh, Saudi Arabia

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SPIO. At low levels, ROS generation appears to be involved in regulating normal cell functions.

On the other hand, macrophages membrane receptor expression assessed using flow cytometer and iNOS and Arginase1 activity measurement were performed to characterize the phenotype of M1 and M2 BMDM before and after their magnetic labeling. M1 and M2 macrophages was found to maintain their respective and characteristic polarization profile. However, a minor attenuation in surface membrane receptor expression and additional release of nitrite as iNOS activity marker was detected probably due to ROS release.

Finally, to evaluate the biodistribution of intravenously injected macrophage subpopulations in COPD, whole-body MRI investigation was performed on mice receiving 1 million of M1 or M2 amine modified PEGylated SPIO (SPIO-PEG-NH2) macrophages using a Bruker 4.7T scanner. Mice were first intrapulmonary exposed to a bacterial lipopolysaccharide (LPS) liquid suspension using a microSprayer aerosolizer to develop a COPD inflammatory model with the most effect observed 48 hours post exposition chosen as macrophages injection time point. Susceptibility-weighted gradient echo sequence was used to evaluate the biodistribution of macrophages subpopulations in organ of interest (i.e., liver, spleen and kidneys) and ultra-short (UTE) radial sequence was used to detect the migration of macrophages subpopulations to the lung [3].

As expected, M1 and M2 labeled macrophages were mainly detected in the spleen and to a lower extent in the liver with the maximum signal attenuation observed 2 hours post injection (Figure1c). No variation in M1 and M2 macrophages biodistribution was observed in the systemic organs of interest. However, a higher detection for M2 macrophages subsets was detected in the lung of COPD group. This preferential homing of M2-polarized macrophages to the LPS-induced inflammation site in the lung is in line with their proposed immuno-modulating functions.

In conclusion, carboxylic or amine modified PEGylated SPIO nanoparticles have been shown to be safe and have a higher labeling efficiency while not affecting neither the polarization nor the biodistribution of macrophages sub-populations. A preferential migration of magnetic labeled M2 macrophages was detected in the lung of COPD animals. This strategy will certainly pave the way

to evaluate, using a noninvasive imaging modality, the role of macrophages and their polarization in the orchestration and resolution of inflammation.

References [1] Al Faraj et al., Contrast Media and Molecular Imaging, Volume 8, Issue 2 (2013), pages 193â&#x20AC;&#x201C; 203.

[2] Al Faraj et al., International Journal of Molecular Sciences. Accepted manuscript.

[3] Al Faraj et al., Radiology, Issue 263 (2013), pages 169-78.

Figures

Figure 1: (a) Quantitative analysis of iron content in M1 and M2 macrophages after labeling with either SPIO, SPIO-PEG, SPIO-PEGCOOH or SPIO-PEG-NH2, assessed using either spectrophotometer (upper row) or magnetophoresis (lower row). (b) Percentage of viability (assessed by MTT), ratio of red fluorescence divided by green fluorescence (assessed by JC-1 for mitochondrial membrane potential), and reactive oxygen species generation (assessed by ROS assay) of M1 labeled macrophages (upper row) or M2 labeled macrophages (lower row), compared to control non-labeled macrophages. (c) MR images of lung acquired using UTE radial sequence (upper row), liver (middle row) and spleen and kidneys (lower row) acquired using susceptibility-weighted gradient echo sequence pre- and post-injection of SPIO-PEG-NH2 labeled M2 macrophages.

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Oral Anticancer Activity of Engineered Nanomaterials

1

Hisham A. Alhadlaq1,2 1 Maqusood Ahamed

hhadlaq@ksu.edu.sa

King Abdullah Institute for Nanotechnology, King Saud University, Riyadh, Saudi Arabia 2 Department of Physics and Astronomy, King Saud University, Riyadh, Saudi Arabia

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apoptosis. The present study warrants further investigation on anticancer activity of ZnO and Fe3O4 NPs in relevant animal models.

Keywords: Nanotechnology; Cancer therapy; ZnO; Fe3O4; Apoptosis

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Cancer is a leading cause of death worldwide, accounting for 7.6 million deaths (around 13 % of all deaths) in 2008. Even more serious is the recent projection by the World Health Organization (WHO), which anticipates total cancer cases to be over double by the year 2030. One of the major challenges in cancer therapy is to improve the selectivity and efficacy of anticancer agents and reduce their side effects to improve quality of life for cancer patients. With the rapid developments in nanotechnology and nanomaterials, new types of drugs are being explored that have the potential to overcome problems with existing anticancer therapies. Nanomaterials are increasingly being recognized for their potential applications in biomedicine such as imaging, drug/gene delivery and cancer therapy, due to their unique physicochemical properties. Recent preliminary studies suggested that some of the inorganic nanoparticles (NPs) have potential to induce toxicity in a cell-specific and proliferationdependent manner with rapidly dividing cancer cells being the most susceptible and quiescent cells being the least sensitive. Clearly the type of cell in question is important when considering toxicity of some of NPs toward mammalian cells.

We investigated whether ZnO and Fe3O4 NPs induced toxicity in a cell-specific manner and determine the possible mechanisms of toxicity caused by these NPs in cancer cells. We have utilized different types of cancer cells and normal cells. Results showed that both ZnO and Fe3O4 NPs exert distinct effects on cell viability via killing of cancer cells while posing no toxicity on normal cells. Molecular data suggested that NPs selectively induce apoptosis in cancer cells, which is likely to be mediated by reactive oxygen species via p53; bax/bcl-2 and caspase-3 pathways, through which most of the anticancer drugs trigger

Oral Lamiaa M.A.Ali

1

Miss_limo@yahoo.com pasquina.marzola@univr.it lasheras@unizar.es palacio@unizar.es

P. Marzola2* E. Nicolato2, S. Fiorini2 M. de las Heras Guillamón3* R. Piñol1, L. Gabilondo1 A. Millan1 and Fernando Palacio1*

Instituto de Ciencia de Materiales de Aragón, CSIC – Zaragoza University, Zaragoza, Spain.

2 Department of Computer Sciences and Neurological Sciences, Neuropsychological, Morphological and Movement, Section of Anatomy and Histology, Verona University, Verona, Italy.

3 Department of Animal Pathology, Unit of Histology and Anatomical Pathology, Zaragoza University, Zaragoza, Spain

Magnetic resonance imaging (MRI) is considered as one of the most promising noninvasive diagnostic tools in medical science. Since it provides threedimensional anatomical images with high spatial resolution in the sub-millimeter range [1].

Superparamagnetic iron oxide nanoparticles (SPIONs) are inorganic nanomaterials comprising a class of MRI contrast agents, as they enhance the image contrast and thus improve the sensitivity and specificity of MRI in mapping information from tissues. Thus far, several SPIONs preparations have already been used for clinical practice, especially for liver MRI, such as Ferumoxides (i.e. Endorem® in Europe, Feridex® in the USA and Japan) coated with dextran [2], and Ferucarbutran (i.e. Resovist® in Europe and Japan) coated with carboxydextran [3]. The magnetic nanoparticles studied here are part of a synthetic platform for SPIONs based on the use of polymers. They are made from biocompatible components, and are stable as a colloidal aqueous fluid in phosphate buffered saline (PBS) at pH = 7.4 and human body temperature [4].

This nanoplatform has an outstanding capacity for multifunctionalisation that, apart from magnetism has already been proved for: luminescence (fluorescein, rhodamine, and lanthanides), radiochemical tracing (In111), antibodies, molecular thermometry [5], and anticancer drugs (cis-Pt). They consist of: 1) hydrophobic polymer [poly(4-vinyl pyridine) (P4VP)] core encapsulating maghemite (γ-Fe2O3) nanoparticles, which is densely coated with 2) hydrophilic polymer chains [polyethylene glycol (PEG)] that may contain at the outer end various functionalities as mentioned above. In the sample used in this work, a part of the PEG chains are functionalized with –COOH groups to provide sites for the anchoring of antibodies or peptides to

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Biodistribution studies of polymer coated superparamagnetic iron oxide nanoparticles using Magnetic Resonance Imaging

nanoparticle surface so they can be directed to specific targets. The iron oxide nanoparticles in the P4VP core have a diameter of 13 nm and they are embedded within the P4VP matrix, thus preventing agglomeration. The core and the polymeric coatings have a total hydrodynamic diameter of 163 nm.

Since the rationale of the synthesis of these ferrofluids is to improve current commercial contrast agents, in vitro relaxation measurements for ferrofluids as a function of core diameter have been carried out and compared to Endorem® [6].

In addition, the blood compatibility of the ferrofluids have been verified [7] Longitudinal and transversal relaxation rates (1/T1 and 1/T2) were plotted as a function of iron concentration and r1 and r2 relaxivities were obtained by the slope of the fitting straight line.

The performance of the ferrofluid as a contrast agent in cerebral perfusion experiments compared to Endorem® has been investigated. The mapping of the cerebral blood flow (CBF) and cerebral blood volume (CBV) were carried out following the bolus tracking method (first passage) [8]. Results clarify the effect of both Endorem® and ferrofluids on the signal intensity in vivo, however, Endorem® decreases the signal intensity more than ferrofluids. To evaluate the performance of the ferrofluid as a contrast agent compared to Endorem® in steady-state condition, T2*-weighted images in brain were acquired before (pre) and during 2h after (post) injection of ferrofluids and Endorem®. Results show that few minutes after injection of ferrofluids and Endorem®, a decrease in the signal intensity was observed for both contrast agents (Fig.1B, 1F), in contrast, at two hours after injection, a hypointense brain was observed for mice injected with Endorem®

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(Fig.1C), however, a cleared brain was observed for mice injected with ferrofluids that emphasizes the clearance of ferrofluids from the circulation (Fig.1G).

To evaluate the biodistribution of ferrofluids and Endorem® in the mouse body, T2 and T2*weighted images were performed. T2 and T2*weighted images were acquired before (pre), 5min-2h, 24h, 7days, 15days, 30days, and 60days after (Post) injection. Results show the accumulation of ferrofluids and Endorem® in the liver few minutes after injection, Endorem® is completely cleared from the liver 30 days after injection, however, ferrofluid is cleared from the liver 60 days after injection. No accumulation of ferrofluids and Endorem® was detected in kidney using MRI methods. The presence of ferrofluids and Endorem® in tissues (liver, kidney, spleen, lungs, and heart) at different time points (2 hours, 24 hours, 7 days, 15 days, 30 days and 60 days) was determined by Prussian blue assay.

Furthermore, histological studies were carried out; results show that no significant histopathological changes were detected Fig. 2. We can conclude that these ferrofluids act as long-term contrast agents without generating any notable histological lesions in mice organs over a period of 60 days.

[7] Lamiaa M.A. Ali, M. Gutiérrez, R. Cornudella, J.A. Moreno, R. Piñol, L. Gabilondo, A. Millán and F. Palacio, J. Biomed. Nanotechn. (in press) (2013).

[8] O. Haraldseth, R.A. Jones, T.B. Müller, A.K. Fahlvik, A.N. Oksendal, J Magn Reson Imaging, 6(1996)714.

References

Figure 2: Hematoxylin and Eosin staining in mouse liver before injection (A) and 7 days after injection with Endorem® (B) and ferrofluids (C). Images are at 40X magnifications.

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NANOBIO&MED 2013

Figure 1: T2*-weighted images for a mouse brain before (A, E), 5 min (B, F), and 2h (C, G) after injection of Endorem® (upper panel) and ferrofluids (lower panel). rCBV maps for ferrofluids and Endorem® are shown in D and H respectively.

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[1] C.M. Lee, H.J. Jeong, E.M. Kim, D.W.Kim,S.T. Lim,H.T.Kim, I.K.Park, Y.Y.Jeong,J.W.Kim, M.H.Sohn, Magn Reson Med, 62(2009)1440.

[2] R. Weissleder, D.D.Stark, B.L.Engelstad, B.R.Bacon, C.CCompton, D.L.White, P.Jacobs, J.Lewis, American Journal of Roentgenology, 152(1989)167.

[3] P. Reimer, E.J. Rummeny, H.E. Daldrup, T. Balzer, B. Tombach, T. Berns, P.E. Peters, Radiology, 195 (1995)489.

[4] A. Millán A, F. Palacio, A. Falqui, E. Snoeck, V. Serin, A. Bhattacharjee, V. Ksenofontov, P. Gütlich, I. Gilbert, Acta Materialia 55(2007)2201.

[5] C. Brites, P. Lima, N.J.O. Silva, A. Millán, V. Amaral, F. Palacio and L. Carlos. Adv. Mater.

22(2010)4499.

[6] H. Amiri, P. Arosio, M. Corti, A. Lascialfari, R. Bustamante, A. Millán, N.J.O. Silva and F. Palacio, Magn. Res. in Medicine, 66, 17151721, (2011).

Figures

Oral Voltammetric glucose sensor using poly(2,5 dimethoxy aniline) as a polymer support

Prabhuraj Balakrishnan 2 S. Chinnaiah

1

ccsivakumar@cecri.res.in 1

PhD Student, School of Chemical Engineering and Analytical Science (CEAS), The University of Manchester, Manchester M13 9PL, UK. Email: prabhuraj.balakrishnan@postgrad.manchester.ac.uk 2 Scientist, Electrodics and Electrocatalysis (EEC) Division, CSIR-Central Electrochemical Research Institute (CECRI), Karaikudi-630006. Tamilnadu, INDIA

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A glucometer is a medical device for measuring levels of glucose concentration in the blood, depending on the level, administration of a drug might be required for the patient. Test strips are used in glucometers to interact with a patient’s drop of blood. This work mainly focuses on the synthesis and fabrication of sensor material used in the test strips of the glucometer.

A non-enzymatic voltammetric sensor has been constructed for the detection of glucose by using nanofibrillar morphology of MPBA-Au-PDMA matrix. This was achieved by simple three step process involving electrochemical processes namely voltammetric techniques. PDMA (Poly dimethoxy aniline) is exclusively fabricated as nonenzymatic glucose sensor platform because the presence of two methoxy groups in the PANI (Poly Aniline) backbone shows better support for immobilization of Au nanocatalyst followed by SAM (Self Assembled Monolayer) attachment of 4Mercapto phenyl boronic acid (MPBA) groups. The sensor platform was characterized by Cyclic voltammetry and Scanning Electron Microscopy (SEM). The resulting biosensor platform shows good sensitivity with linearity for the detection of Glucose between 0.25 mM to 50 mM at a pH of 7.2 in Phosphate Buffer solution (PBS) similar to physiological conditions of blood.

Several samples were synthesized by changing the experimental parameters such as method of deposition of polymer film, concentration of Auric chloride [HAuCl4] solution, concentration of MPBA [(HO)2-B-C6H4-SH] solution and their immersion periods. These sensor materials were tested to find their use as one-time non reusable test strips for glucose meters. To be in an engineering point of view, cost for all samples were calculated.

Finally optimization was carried out and the best

material was identified. Hence a new sensor material has been fabricated.

References [1] J. Liu, M. Agarwal et al., “Glucose sensor based on organic thin film transistor using glucose oxidase and conducting polymer “ J.Sensors and Actuators B: Chemical, Volume 135, Issue 1, 10 December 2008, Pages 195-199.

[2] Min Pan et al.,“A novel glucose sensor system with Au nanoparticles based on microdialysis and coenzymes for continuous glucose monitoring” J. Sensors and Actuators A: Physical, Volume 108, Issues 1–3, 15 November 2003, Pages 258-262.

[3] Gabriele Favero et al.,“Preparation and characterization of a chemically modified electrode based on ferrocene-tethered βcyclodextrin self assembled monolayers” Microchemical Journal, Volume 76, Issues 1–2, February 2004, Pages 77-84.

[4] Ping He et al.,” ESR-electrochemistry in-situ studies on chemically modified electrodes” Journal of Electroanalytical Chemistry, Volume 405, Issues 1–2, 12 April 1996, Pages 217-22.

[5] Xinjian Huang et al.,“Electrochemical characteristics of conductive carbon cement as matrix for chemically modified electrodes” J.Analytica Chimica Acta, Volume 300, Issues 1–3, 20 January 1995, Pages 5-14.

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Figure 2: Optimisation graph of Detection Range (mM) Vs Cost of material for samples A to H.

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Figure 1: Cyclic voltammogram of MPBA-Au-PDMA film on GCE recorded in 0.1 M PBS (pH-7.2) for different additions of glucose (a) 0mM (b) 1mM (c) 2mM (d) 3mM (e) 4mM (f) 5mM (g) 6mM (h) 7mM (i) 8mM for one of the samples.

Oral 1,2

Interdigitated biosensor for multiparametric monitoring of bacterial biofilm development

Sheila Becerro 1,2 J. Paredes and 1,2 S. Arana

sbecerro@cicmicrogune.es 1

CIC microGUNE, Goiru Kalea 9, 20500 Arrasate-Mondragon, Spain CEIT-IK4 and Tecnun (University of Navarra), Paseo de Manuel Lardizรกbal 15, 20018 Donostia-San Sebastiรกn, Spain 2

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Adhesion and development of bacterial biofilms onto any kind of surfaces causes numerous problems in a wide variety of sectors, and more particularly, in those related with the medical environment or the industry. Specifically, medical implants are frequently infected due to bacterial adhesion threatening the health of the patients and involving additional hospital costs [1].

Biofilms are formed when bacteria adhere to surfaces and excrete a sticky and viscous substance that forms a complex and heterogeneous polymeric structure.

This extracellular matrix increases the antimicrobial resistance of the adhered microorganisms by blocking the access of antibiotics through it [2].

Thus, treatment and disposal of these kinds of infections is often hampered by the surrounding structure and by the total lack of symptoms in the early stages of the infectious process. Therefore, it is necessary to find new methods for the early detection of biofilm development and growth since the first steps.

One of the most widely used detection methods for microorganism detection is the electrical impedance spectroscopy [3]. The working principle is based on the impedance changes induced after cell adhesion onto the measured electrodes [4].

Sensors based in interdigitated micro and nanoelectrode arrays are very commonly used for this purpose because they offer notable features such as a large sensitive area in a limited space. In this work, chromium-gold interdigitated electrodes (a) have been designed and fabricated on silicon wafers using conventional lithographic techniques. ยกError! No se encuentra el origen de la referencia. (b) shows the experimental setup developed ad hoc for electrical impedance spectroscopy.

Measurements have been supported by a multiplexer system [5] that allows an automated

sampling. shows the results obtained for the impedimetric monitoring of bacterial biofilm adhesion and development. The presence of microorganisms has been detected since the first steps of bacterial adhesion.

On the other hand, so as to enhance both the specificity and the sensitivity of the detection method, electrochemical monitoring through cyclic voltammetry has been conducted. Measurements have been taken using the redox cycling technique that allows signal amplification by the use of two working electrodes: collector and generator. By exciting one electrode at a potential that allows the reduction of the species and the other electrode at the oxidation potential, species are continuously being transformed at the generator electrode and are converted back to their original form at the collector.

Moreover, the measurement of the temperature onto the surface where biofilm deposits can give additional information about its metabolic activity. Real-time surface temperature measurements can also be used to correct the thermal drifts of the monitoring curves.

For these purposes, a multiparametric sensor has been designed and fabricated on thermally oxidized silicon wafers and on layers of Cyclic Olefin Polymer (COP). COP increases the adhesion of bacteria and its malleability allows its use in 3D applications. For electrochemical experiments, the choice of biosensors based on interdigitated electrodes has been kept because of their good performance [6]. As the gap between electrodes is very small, molecules reach the opposite electrode immediately and the resulting current is increased.

Two interdigitated working electrodes of titaniumgold, a titanium-silver reference electrode and a titanium-platinum counter electrode have been deposited for the electrochemical sensing part (a)

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and (b)). Moreover, a titanium-platinum temperature sensor has been added onto the chip

Figure 2: Impedance measurement during the development of a microbiological culture of S. epidermidis.

(c).¡Error!

No se encuentra el origen de la referencia.(d) shows the developed setup for multiparametric monitoring. The measurements and characterizations carried out proved the linearity of the temperature sensor that has a TCR value of 1950 ppm/ºC. Moreover, the first measurements carried out in order to compare impedimetric and electrochemical techniques have proved that the specificity and the sensibility have been improved.

Figure 3: Interdigitated microelectrode array based sensor (a) on silicon substrate and (b) on COP polymer; (c) integrated temperature sensor and (d) experimental setup for multiparametric measurements.

[1] von Eiff C, Jansen B, Kohnen W, Becker K. Drugs, 65 (2005) 179-214.

[2] Donlan RM. Emerg Infect Dis, 8 (2002) 881890.

[3] Cady, P., Dufour, S. W., Shaw, J., Kraeger, S. J. J. Clin. Microbiol., 7 (1978) 265-272.

[4] Mamouni J, Yang L. Biomed Microdevices, 13 (2011) 1075-1088.

[5] Becerro, S., Benavente, A., Paredes, J. & Arana, S. XXIX Congreso Anual de la Sociedad Española de Ingeniería Biomédica (2011).

[6] Skjolding LHD, Spegel C, Ribayrol A, Emnéus J, Montelius L. Journal of Physics: Conference Series, 100 (2008) 1-4.

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References

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Figure 1: (a) Interdigitated microelectrodes array based sensor and (b) experimental setup for electrical impedance measurements.

Invited In vivo recordings of brain activity using organic transistors 1

Christophe Bernard

2,3

D. Khodagholy1, T. Doublet1,2,3,4 M. Gurfinkel1, P. Leleux1,2,3,4 P. Quilichini2,3, A. Ghestem2,3 E. Ismailova1, T. Herve4 S. Sanaur1 and G. G. Malliaras1

Department of Bioelectronics, Ecole Nationale Supérieure des Mines, CMP-EMSE, MOC, 13541 Gardanne, France 2 Aix Marseille Université, INS, 13005, Marseille, France 3 Inserm, UMR_S 1106, 13005, Marseille, France 4 Microvitae Technologies, Pôle d'Activité Y. Morandat, 13120 Gardanne, France.

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Most breakthroughs in our understanding of the basic mechanisms of information processing in the brain have been obtained by means of recordings from electrodes implanted into, or placed on the surface of the brain. In vivo electrophysiological recordings of neuronal circuits are also necessary for diagnosis purposes and for brain-machine interfaces.

State-of-the-art recordings are currently performed with microfabricated arrays of metal electrodes, which capture the local field potentials (LFPs) generated by the spatio-temporal summation of current sources and sinks in a given brain volume. However, key technological advances are still needed: the probes must be fully biocompatible (to enable long-term recordings), small/thin (to decrease invasiveness), highly conformable (to comply with the complex 3D architecture of the brain), but most importantly, they must provide an increased SNR through a built-in pre-amplification/processing system.

Organic electronic devices constitute a promising solution because of their mechanical flexibility and biocompatibility. Here we demonstrate the engineering of an organic electrochemical transistor embedded in an ultrathin organic film designed to record electrophysiological signals on the surface of the brain. The device, tested in vivo on epileptiform discharges, displayed superior signal-to-noise ratio, due to inherent amplification, as compared to surface electrodes. Importantly, the organic transistor was able to record activity, which was poorly detected by regular ECoG. This study introduces a new class of biocompatible, highly flexible devices for recording brain activity with superior signal-to-noise ratio (SNR), of great promise for medical applications.

References [1] Khodagholy et al., Nature Communications; 4:1575, 2013.

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Oral Spectroscopic Characterization of Protein-Wrapped Single-Wall Carbon Nanotubes and Quantification of Their Uptake in Macrophages

Cristina Bertulli H. J. Beeson H. Tawfique and Y. Y. S. Huang

cb697@cam.ac.uk

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the BSA molecule binds to the SWNT surface.

Semiconducting SWNTs (s- SWNTs) have a direct band gap. Therefore, photoluminescence emission from isolated s-SWNTs due to exciton recombination is expected (Figure1 (right)). The optical signatures associated with the (6,5) species are red-shifted by ~8 nm (150 eV), while the larger diameter chirality (7,5) nanotubes do not exhibit any noticeable shifts. The shifts in the emission wavelengths are likely due to increased doping of the SWNTs through SWNT-biomolecule charge transfer.[9] The larger shifts and resultant increased doping of smaller diameter nanotubes are also due to preferential wrapping and isolation of the smaller diameter SWNTs by BSA. For the BSA-SWNTs, the intensity of the G+ peak is monitored at different SWNT concentrations to produce a calibration relationship between intensity and concentration for Raman signals. We found that the G-band Raman intensity follows a well-defined power law for SWNT concentrations of up to 30 Îźg/ml in aqueous solution. RAW 264.7 mice macrophages are incubated with BSA-SWNT hybrids. The viability of the macrophages incubated with BSA-SWNTs is studied by monitoring cellular growth and using the redoxbased Alamar Blue assay. Our experiments demonstrate that incubation of BSA-SWNT complexes with macrophages neither affects the cellular growth, nor the cellular viability over multiple cell generations (Figure2). We then determine the uptake of BSA-functionalized SWNTs by macrophages, specifically as a function of time. As mentioned before, the G+ intensity in SWNT Raman spectra can be directly correlated to the nanotube concentration in the sampled region.

The presence of the characteristic SWNT peaks in the Raman spectrum obtained from the cells

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Biomedicine is one area in which single wall carbon nanotubes (SWNTs) have potential for great impact.[1][2][3] However, the toxicological profile of SWNTs remains a significant concern.[4][5][6] In our study, we perform quantitative evaluation of the time-evolution of SWNT uptake in mouse macrophages over a period of three cell cycles.

Macrophages are white blood cells important for the innate and adaptive immune systems of vertebrates[7] and hence represent especially relevant systems to study. Macrophages phagocyte debris and pathogens, and contribute to the initiation of other defense mechanisms, thus playing an important role in the body's response towards foreign objects. SWNTs grown via two different processes (CoMoCAT and P2 ) are investigated to ensure the results are not specific to a single type of SWNT. Both the SWNT types are conjugated with BSA to enhance their biocompatibility. Raman spectroscopy is utilized to monitor the SWNT concentration in the bulk of cell suspension to obtain statistically significant sampling. In the process, we also apply optical absorption and photoluminescence spectroscopy methods to characterize the properties of the BSASWNT dispersions.

Optical absorption spectroscopy offers the first quantifiable characterization of the BSA-functionalized SWNTs. Figure 1(left) shows the absorption spectra for an aqueous solution of BSA and for aqueous dispersions of BSA-CoMoCAT and BSA-P2. The BSA spectrum exhibits peak absorption at ~277 nm.

The same peak is observed in the BSA-CoMoCAT and BSAP2 spectra, but with shifted positions and at much reduced intensities. Since this BSA absorption peak is primarily caused by amino acids with aromatic rings,[8] the observed shift suggests that a change in the protein structure occurs when

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University of Cambridge, JJ Thomson Avenue, Cambridge, United Kingdom

incubated with BSA-CoMoCAT nanotubes (Figure3a) is a simple confirmation that this functionalized nanotube species is uptaken by the macrophages. The average number of nanotubes internalized per cell was found remaining relatively constant over consecutive cell generations (Figure3b). The number of internalized macrophages is found to be ~ 40 x 106 SWNTs/cell for a 60 mm-2 seeding density and ~ 140 x 106 SWNTs/cell for a 200 mm-2 seeding density. Our results show that BSAfunctionalized SWNTs are an efficient molecular transport system with low cytotoxicity maintained over multiple cell generations.

Figure 2: Macrophage viability.

References [1] Krauss T D. Nat. Nanotechnol., 4 (2009) 85.

[2] Liu Y and Wang H, Nat. Nanotechnol., 2 (2007) 20.

[3] Liu Z., Chen K, Davis C, Sherlock S, Cao Q, Chen X and Dai H Cancer Res., 68 (2008) 6652.

[4] Zhao Y, Xing G and Chai Z, Nat. Nanotechnol., 3 (2008) 191.

[5] Poland C. A, Duffin R, Kinlock I, Maynard A,Wallace W. A. H, Seaton A, Stone V, Brown S, MacNee W. and Donaldson K, Nat. Nanotechnol., 3 (2008) 423.

[6] Kostarelos K, Nat. Biotechnol., 26 (2008) 774.

[7] Mosser D. M. and Edwards J. P, Nat. Rev. Immunol., 2008, 8, 958.

[8] Goldfarb A, Saidel L. and Mosovich E, J. Biol.

Chem., 1951, 193, 397.

[9] O’Connell M. J, Eibergen E. E. and Doorn S. K, Nat. Mater., 2005, 4, 412.

Figure 3: a) Raman spectra for macrophages incubated with BSACoMOCAT. b) Amount of BSA-CoMoCAT complexes uptaken.

Figures

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Figure 1: (left) Absorption spectra. (right) PLE spectrum. Each resonance is labeled with the chiral index of the corresponding SWNT and is denoted by ◊. The symbols □, + and X represent phonon sidebands, EET, and EET between sidebands of donors and excitons of acceptor nanotubes in small bundles, respectively.

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Oral Geometrical and mechanical fine structure of peptidoglycans in living Streptococcus bacteria studied by AFM nanomechanical mapping

1

Arkady Bitler 2 R. Dover and 2 Y. Shai

arkady.bitler@weizmann.ac.il

1

Department of Chemical Research Support, Faculty of Chemistry, Weizmann Institute of Science, Rehovot, P.O.B. 26, Israel, 76100 2 Department of Biological Chemistry, Faculty of Biochemistry, Weizmann Institute of Science, Rehovot, P.O.B. 26, Israel, 76100

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References

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[1] Bierne, H., and Dramsi, S., Cur.Opin.Microbiol., 15 (2012), 715-723.

[2] Tripathi, P., et al., Micron, 43 (2012), 13231330.

[3] Saar-Dover, R., et al., PLOS Pathogens, 9 (2012), e1002891.

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Bacterial peptidoglycan is an important component of the cell wall, maintaining turgor pressure and cell shape. The peptidoglycans are responsible for the transitions between different physiological states of bacteria: from biofilm formation to active growth and division and other functional properties of bacterial cell. Moreover the distribution of surface proteins contributing to the infection process is directly coupled to the peptidoglycan three-dimensional structure [1-2].

We studied the nanoscale architecture of peptidoglycan and associated proteins at the surface of living Streptococcus bacteria by atomic force microscopy (AFM). The bacterial cells were trapped in filter pores and imaged in DD water and buffer in PeakForce QNM (quantitative nanomechanics) mode allowing to acquire a topography and elasticity and adhesion maps simultaneously [3]. The topographical surface structures exhibit typical glycan strands arranged in helical manner and decorated by proteins of various sizes. We found that aside from the synthesis centers the strands can be interrupted by spots with net-like structures which interconnect a few neighbor strands. Furthermore it was observed that large proteins cover separated parts of the strands and net-like structures are covered by much smaller species. The analysis of adhesion maps suggests that there exists a set of adhesive bands directed perpendicularly to the glycan strands. The results are supplemented by elements of flooding analysis enabling to visualize and quantify these features.

Oral ELISA - like nano-immuno assay for the proteomic analysis of malignant gliomas.

Elettra - Sincrotrone Trieste S.C.p.A. , S.S. 14 - km 163,5 in AREA Science Park 34149 Basovizza, Trieste, Italy

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The quantitative analysis of protein markers for malignant glioma is becoming relevant in the diagnosis and prognosis for this kind of tumors.

Despite the efforts in cancer therapy, the prognosis of this common brain tumor remains dismal. In order to face this problem we implemented a promising strategy for the high throughput analysis of few glial cells with potential capability of real-time pathological screening and sub typing of brain tumors. We developed an ELISA like nano-immuno array [1] for proteomic/secretomic analysis suitable for low sample volumes.

In particular, we first fabricate DNA nanoarrays exploiting nanografting [2,3], a tip assisted AFM deposition technique used in order to produce spatially confined monolayers of thiolated oligonucleotides on gold surfaces. By exploiting DNA-directed-immobilization (DDI) of DNA-protein conjugates, we are able to immobilize antibodies for the detection of a specific protein of interest.

From the analysis of AFM topographic profiles of the nanoarray before and after the incubation with a cellular sample, we quantitatively determine the concentration of the protein of interest in the volume. As a proof of concept, we immobilize an antibody specific for Glial Fibrillary Acidic Protein (GFAP), a biomarker that belongs to the family of intermediate filaments, crucial in the differentiation of central nervous system cells. The calibration curve in the nanomolar range obtained with this nanoscale assay will be compared with a standard ELISA assay. Results about the detection of GFAP in cellular lysate will also be presented.

The integration of our nanoarray with microfabricated wells for sorting and hosting cells (ideally few cells per well), will be discussed.

Alessandro Bosco M. Ganau, A. Palma S. Corvaglia, P. Parisse A. P. Beltrami, D. Cesselli G. Scoles and L. Casalis

alessandro.bosco@elettra.trieste.it

References [1] Bano F, Fruk L, Sanavio B, Glettenberg M, Casalis L, Niemeyer CM, Scoles G, Nano Lett. 9 (2009) 2614.

[2] Liu M, Liu GY, Langmuir 21 (2005) 1972.

[3] Mirmomtaz E, Castronovo M, Grunwald C, Bano F, Scaini D, EnsaďŹ AA, Scoles G, Casalis L, Nano Lett. 8 (2008) 4134.

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Oral Multifunctional lipid nanoparticles dedicated to RNAi screening

Jonathan Bruniaux 2 E. Sulpice 2 F. Mittler , I. Texier1 2 X. Gidrol and 1 F. Navarro

1, 2

1

CEA, LETI MINATEC, Technologies for Healthcare and Biology division, 17 rue des martyrs, 38054 Grenoble Cedex 9, France 2 CEA, Life sciences division, iRTSV, Biomics, 17 rue des martyrs, 38054 Grenoble Cedex 9, France

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Figures

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Fig.3.). These results show efficiency close to that obtained with commercial lipoplexes. Further investigations are ongoing to investigate the intracellular distribution of the “nanoparticlesiRNA” complex.

The association of synthetic siRNA with the benefits of nanotechnology should open the way to new biomedical applications in the near future.

Figure 1: structure of lipid nanoemulsions, before (left) and after (right) incorporation of cationic compounds.

Figure 2: Dot plots obtained by FACS displaying the down regulation of GFP expression.

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Since its discovery fourteen years ago, investigations on RNA interference in biology and medicine are growing with applications ranging from molecular genetics to design of new therapeutic strategies. Indeed, synthetic siRNA (small interfering RNA) provide a simple and effective gene silencing means through a sequence specific down-regulation of the complementary messenger RNA. However, naked siRNA are highly sensitive to the degradation enzymes (nucleases) and does not cross the cell membrane due to its large molecular weight (13kDa) and anionic nature. Thus, delivery systems are strongly required to facilitate its distribution to its intracellular sites of action.

Among the considered solutions, with their unique properties (targeting, monitoring, endosomal escape promoting …), nanoparticles are emerging as a promising approach in the specific delivery of siRNA. Lipid nanoparticles were specially brought to our attention for this application.

By incorporating some cationic compounds to lipid nanoemulsions, the electrostatic bonds establishment with negative charges of siRNA (Fig.1.) has been improved. The structure of cationic lipid nanoemulsions has been optimized with a design of experiment to isolate the most relevant formulation. Each design of particle has been studied (physical chemical properties, colloidal stability, especially in biological medium, toxicity) before checking the interaction with siRNA. Cationic lipid nanoparticles allow complexation with TAMRA-stained siRNA, as demonstrated by gel retardation assay.

Furthermore, in vitro transfection using a tumoral cell model overexpressing the green fluorescent protein (GFP) show a significant down-regulation of this targeted protein expression (Fig.2. and

jonathan.bruniaux@cea.fr

Figure 3: Microscopy imaging of down regulation of GFP expression with cationic lipid nanoparticles following times.

306

.

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Label-free Gold Nanoparticle Biosensor for alpha-fetoprotein Detection

Wei-Hung Chen Y. -T. Chiang C. -Y. Hsu Y. -H. Hsieh and K. -J. Lin*

National Chung-Hsing University, 250, Kuo-Kuang Road, Taichung, Taiwan (R.O.C.)

esehsnu@gmail.com; kjlin@dragon.nchu.edu.tw

Here we present a new highly sensitive biosensor approach which has the ability to determine 5~100 ng/ml alpha-fetoprotein (AFP) quantitatively using gold nanoparticle arrays slightly embedded in glass substrates which can be quickly prepared by onestep microwave-plasma dewetting process [1].

Without labeling second antibodies and fluorescence dyes for enhancing sensitivity, AFP coupling to anti-AFP immobilized on the substrate can be directly monitored by the change in the local surface plasmon resonance (LSPR) band of gold nanoparticles. The specificity was further tested by detecting AFP in human IgG solution, and the LSPR-Au biosensor also showed a good linear relationship between LSPR band intensity and AFP concentration in the range of 5~100 ng/ml. Having advantages of low-cost and simple optical setup (which is composed of only one light source and one photodiode, and no gratings are needed), this LSPR-Au biosensor system provide a promising application in disposable biochips for point-of-care diagnostics.

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Oral

References

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307

[1] Chuen-Yuan Hsu, Jing-Wen Huang and KuanJiuh Lin, Chem. Commun., 47 (2011) 872-874.

Oral Design of near-infrared fluorescent bioactive conjugated functional iron oxide nanoparticles for optical detection of colon cancer

Enav Corem-Salkmon S. Margel

enavcorem@gmail.com

The Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat-Gan, 52900, Israel

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Background: Colon cancer is one of the major causes of death in the Western world [1]. Early detection significantly improves long-term survival for patients with the disease [2]. Near-infrared (NIR) fluorescent nanoparticles hold great promise as contrast agents for tumor detection. NIR offers several advantages for bioimaging compared with fluorescence in the visible spectrum, ie, lower autofluorescence of biological tissues, lower absorbance, and consequently deeper penetration into biomatrices [3].

Methods and results: NIR fluorescent iron oxide nanoparticles with a narrow size distribution were prepared by nucleation, followed by controlled growth of thin iron oxide films onto cyanine NIR dye conjugated gelatin-iron oxide nuclei. For functionalization, and in order to increase the NIR fluorescence intensity, the NIR fluorescent iron oxide nanoparticles obtained were coated with human serum albumin containing cyanine NIR dye.

Leakage of the NIR dye from these nanoparticles into phosphate-buffered saline solution containing 4% albumin was not detected. The work presented here is a feasibility study to test the suitability of iron oxide-human serum albumin NIR fluorescent nanoparticles for optical detection of colon cancer.

It demonstrates that encapsulation of NIR fluorescent dye within these nanoparticles significantly reduces photobleaching of the dye.

Tumor-targeting ligands, peanut agglutinin and anticarcinoembryonic antigen antibodies (αCEA), were covalently conjugated with the NIR fluorescent iron oxide-human serum albumin nanoparticles via a poly(ethylene glycol) spacer.

Specific colon tumor detection was demonstrated in chicken embryo and mouse models for both nonconjugated and the peanut agglutininconjugated or αCEA-conjugated NIR fluorescent

iron oxide-human serum albumin nanoparticles [4].

Conclusion: Conjugation of peanut agglutinin or αCEA to the nanoparticles significantly increased the fluorescence intensity of the tagged colon tumor tissues relative to the nonconjugated nanoparticles.

References [1] Franziska A, Ulrike S, The International Journal of Biochemistry & Cell Biology, 12 (2009) 2356-2359.

[2] Majek O, Gondos A, Jansen L, Emrich K, Holleczek B, Katalinic A, Nennecke A, Eberle A, Brenner H, British Journal of Cancer 106 (2012) 1875-1880.

[3] Santra S, Malhotra A., Wiley Interdiscip Rev Nanomed Nanobiotechnol,3 (2011) 501–510.

[4] Corem-Salkmon E, Perlstein B, Margel S, International Journal of Nanomedicine, 7 (2012) 5517-5527.

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Figures

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Figure 2: A typical experiment illustrating a mouse colon treated with (A) PNA and (B) ÎąCEA-conjugated IO/HSA NIR fluorescent nanoparticles. Each set (A, B, and C) of experiments exhibits a color photograph, a fluorescent image and a logarithmically scaled fluorescent image. Image C depicts an untreated tumor indicating a negligible level of tumor autofluorescence. B and C illustrate that the bioactive-conjugated fluorescent IO/HSA nanoparticles selectively labeled the LS174T tumors and left the surrounding nonpathological tissue relatively unlabeled, with a signal to background ratio of 1xe2.5.

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Figure 1: Fluorescence imaging of tumors on chicken embryo CAM : (A) Merged fluorescent and bright light images of a typical experiment of LS174T tumor cell line implanted on chicken embryo CAM treated with PNA (I), ÎąCEA (II) and glycine (III)-conjugated IO/HSA NIR fluorescent nanoparticles; (B) Quantification of the fluorescence intensity of the tumors averaged over the surface area as calculated by ImageJ software. Note that the vertical axis is logarithmically scaled.