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Publishing Alliance

2011 MRS Spring Meeting & Exhibit

April 25-29, 2011 | San Francisco
Meeting Chairs: Ping Chen, Chang Beom-Eom, Samuel S. Mao, Ryan O'Hayre

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Symposium Y : Functional Two-Dimensional Layered Materials

2011-04-26 Show All Abstracts

Symposium Organizers

AlexanderA. Balandin University of California-Riverside

Andre Geim University of Manchester

Jiaxing Huang Northwestern University

Dan Li Monash University

Symposium Support

Cambridge NanoTech Inc

Elsevier Ltd.

Y1: Synthesis and Processing of Graphene I

Session Chairs

Jiaxing Huang

Rodney Ruoff

Tuesday PM, April 26, 2011

Room 3009 (Moscone West)

9:30 AM - **Y1.1

History and Prospects for Graphene-based Materials.

Rodney Ruoff ¹
¹Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States

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10:00 AM - **Y1.2

Synthesis and Applications of Graphene, Graphene Nanoribbons and Other Carbon Nanomaterials.

James Tour ¹
¹Smalley Institute, Rice University, Houston, Texas, United States

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10:30 AM - Y1.3

Properties of Fluorinated Graphene Films.

Jeremy Robinson ¹, James Burgess ¹, Chad Junkermeier ¹, Stefan Badescu ¹, Thomas Reinecke ¹, Keith Perkins ¹, Maxim Zalalutdinov ¹, Jeffrey Baldwin ¹, James Culbertson ¹, Paul Sheehan ¹, Eric Snow ¹
¹, Naval Research Laboratory, Washington, District of Columbia, United States

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10:45 AM - Y1.4

High Quality Bilayered Graphene Sheets from One-Step Electrochemical Exfoliation.

Ching-Yuan Su ¹, Ang-Yu Lu ¹, Lain-Jong Li ¹
¹Research Center for applied science, Academia Sinica, Taipei Taiwan

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11:00 AM - *

Break

11:30 AM - **Y1.5

Advances in Graphene Chemistry.

Robert Haddon ¹
¹Center for Nanoscale Science and Engineering, University of California, Riverside, California, United States

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12:00 PM - Y1.6

Chemical Vapour Deposition (CVD) Growth of Graphene and Few-layered Graphene on Different Crystallographic Orientations of the Copper Grains.

Cecilia Mattevi ¹, Hokwon Kim ¹, Manish Chhowalla ²
¹Materials Department, Imperial College London, London United Kingdom, ²Department of Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States

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Integration of graphene into practical electronic devices necessitates large-scale fabrication of high quality thin films. Chemical vapour deposition (CVD) of graphene on copper is a potential scalable route for high quality graphene deposition because is easy to etch, facilitating transfer onto insulating substrates [1]. It has been also demonstrated that atmospheric pressure (AP)CVD, with high partial pressure of CH4, can deposit few- layered graphene films over a large fraction copper surface [2]. To fully understand the growth of graphene with variable thickness, it is necessary to understand the nature of nucleation sites on the copper surface. Moreover, the activation mechanism of the graphene nucleation and density of such sites as a function of the copper morphology, size and crystallographic orientation of grains, are not yet fully understood. Here we demonstrate the thickness dependence of graphene on CH4 (carbon precursor source) flow rate, growth pressure, different polycrystalline microstructures and morphologies of copper foils. We used CH4/H2 mixture to grow graphene by low pressure (LP)CVD (0.1-0.5 Torr) and copper foils which underwent different manufacturing processes. Graphene over ~ 95% of the surface was obtained at low CH4 flow rate (0.5 sccm) on copper foils with uniform crystallographic orientations of the grains. While applying the same growth conditions on copper foils with random crystallographic orientation of the grains, the resulting graphene was bilayer over >60% of the surface and the left over surface was covered by either monolayer or 3 layered graphene film. Higher CH4 flow rate and growth pressure extended the bilayer graphene up to >90 % of the copper surface. Interestingly the higher pressure growth employed on the copper foils with random crystallographic orientation of the grains, lead to homogeneous films of higher quality with respect to the low growth pressure and CH4 flow. Our results reveal that the graphene nucleation sites can be activated differently depending on the CH4 partial pressure, copper crystallinity and morphology. Hence, varying the copper texture should allow the control over the graphene thickness. Optoelectronic properties of the transferred graphene films onto SiO2 are also presented.[1] X. Li, W. Cai, J. An, S. Kim, J. Nah, D. Yang, R. Piner, A. Velamakanni, I. Jung, E. Tutuc, S. K. Banerjee, L. Colombo, and R. S. Ruoff, Science 324, 1312 (2009).[2]S. Bhaviripudi, X. Jia, M.S. Dresselhaus, J. Kong, Nano Lett., 10, 4128 (2010).

12:15 PM - Y1.7

Synthesis of a Pillared Graphene Nanostructure: A Counterpart of Three-dimensional Carbon Architectures.

Maziar Ghazinejad ^{1 2}, Rajat Kanti Paul ¹, Miroslav Penchev ², Jian Lin ¹, Shirui Gue ³, Mihrimah Ozkan ², Cengiz Sinan Ozkan ¹
¹Mechanical Engineering, University of California, Riverside, Riverside, California, United States, ²Electrical Engineering, University of California, Riverside, Riverside, California, United States, ³Chemistry, University of California, Riverside, Riverside, California, United States

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12:30 PM - Y1.8

Facile Synthesis of Large-area Monolayer Graphene Films on Cobalt and Nickel.

Carlo Orofeo ¹, Hiroki Ago ^{1 2}, Yoshito Ito ¹, Masaharu Tsuji ^{1 2}
¹Graduate School of Engineering Sciences, Kyushu University, Fukuoka Japan, ²Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka Japan

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12:45 PM - Y1.9

Second-layer Graphene Growth from Below on Metal Substrates.

Shu Nie ¹, Elena Starodub ¹, Kevin McCarty ¹, Norman Bartelt ¹
¹, Sandia National Laboratories, Livermore, California, United States

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Y2: Synthesis and Processing of Graphene II

Session Chairs

Dan Li

Lain-Jong (Lance) Li

Tuesday PM, April 26, 2011

Room 3009 (Moscone West)

2:30 PM - **Y2.1

Functionalized Graphene Oxide and Graphene: Chemistry and Materials Properties.

Owen Compton ¹, Zhi An ¹, SonBinh Nguyen ¹
¹Department of Chemistry, Northwstern University, Evanston, Illinois, United States

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3:00 PM - **Y2.2

Graphene-based Nanomaterials and Nanostructures: Synthesis, Characterization and Applications.

Hua Zhang ¹
¹School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore

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In this talk, I will summarize the research on synthesis, characterization and applications of graphene-based nanomaterials and nanostructures, which my group has done recently. I will introduce the synthesis and characterization of novel grapheme-based materials [1] and patterned graphene structures [2]. Then I will demonstrate the applications of graphene-based materials in chemical and bio-sensors [3], solar cells [4], electric devices [5], memory devices [6], conductive electrodes [7], cell cultures [8], matrix of MALDI-TOF-MS [9], etc. Reference:[1] (a) X. Y. Qi, K.-Y. Pu, H. Li, X. Z. Zhou, S. X. Wu, Q.-L. Fan, B. Liu, F. Boey, W. Huang, H. Zhang, Angew. Chem. Int. Ed., 2010, DOI: 10.1002/anie.201004497. (b) X. Y. Qi, K.-Y. Pu, X. Z. Zhou, H. Li, B. Liu, F. Boey, W. Huang, H. Zhang, Small, 2010, 6, 663-669. (c) X. Huang, X. Z. Zhou, S. X. Wu, Y. Y. Wei, X. Y. Qi, J. Zhang, F. Boey, H. Zhang, Small, 2010, 6, 513-516. (d) X. Z. Zhou, X. Huang, X. Y. Qi, S. X. Wu, C. Xue, F. Y. C. Boey, Q. Y. Yan, P. Chen, H. Zhang, J. Phys. Chem. C, 2009, 113, 10842–10846.[2] (a) B. Li, G. Lu, X. Z. Zhou, X. Cao, F. Boey, H. Zhang, Langmuir, 2009, 25, 10455-10458. (b) H. Li, J. Zhang, X. Z. Zhou, G. Lu, Z. Y. Yin, G. Li, T. Wu, F. Boey, S. S. Venkatraman, H. Zhang, Langmuir, 2010, 26, 5603–5609. (c) X. Z. Zhou; G. Lu; X. Y. Qi; S. X. Wu; H. Li; F. Boey; H. Zhang, J. Phys. Chem. C, 2009, 113, 19119–19122.[3] (a) Q. Y. He, H. G. Sudibya, Z. Y. Yin, S. X. Wu, H. Li, F. Boey, W. Huang, P. Chen, H. Zhang, ACS Nano, 2010, 4, 3201-3208. (b) Z. J. Wang, X. Z. Zhou, J. Zhang, F. Y. C. Boey, H. Zhang, J. Phys. Chem. C, 2009, 113, 14071–14075.[4] (a) Z. Y. Yin, S. Sun, T. Salim, S. X. Wu, X. Huang, Q. Y. He, Y. M. Lam, H. Zhang, ACS Nano, 2010, 4, 5263–5268. (b) Z. Y. Yin, S. X. Wu, X. Z. Zhou, X. Huang, Q. C. Zhang, F. Boey, H. Zhang, Small, 2010, 6, 307-312.[5] B. Li, X. H. Cao, H. G. Ong, J. W. Cheah, X. Z. Zhou, Z. Y. Yin, H. Li, J. L. Wang, F. Boey, W. Huang, H. Zhang, Adv. Mater., 2010, 22, 3058–3061.[6] (a) J. Q. Liu, Z. Y. Yin, X. H. Cao; F. Zhao; A. Ling; L. H. Xie, Q. L. Fan; F. Boey, H. Zhang, W. Huang, ACS Nano, 2010, 4, 3987–3992. (b) J. Q. Liu, Z. Lin, T. Liu, Z. Y. Yin, X. Z. Zhou, S. Chen, L. H. Xie, F. Boey, H. Zhang, W. Huang, Small, 2010, 6, 1536–1542.[7] S. X. Wu, Z. Y. Yin, Q. Y. He, X. Huang, X. Z. Zhou, H. Zhang, J. Phys. Chem. C, 2010, 114, 11816–11821.[8] S. Agarwal, X. Zhou, F. Ye, Q. He, G. C. K. Chen, J. Soo, F. Boey, H. Zhang, P. Chen, Langmuir, 2010, 26, 2244-2247.[9] X. Z. Zhou, Y. Y. Wei, Q. Y. He, F. Boey, Q. C. Zhang, H. Zhang, Chem. Commun., 2010, 46, 6974–6976.

3:30 PM - Y2.3

Synthesis of High Surface Area Graphene Macroassemblies.

Marcus Worsley ¹, Tammy Olson ¹, Jonathan Lee ¹, Carlos Valdez ¹, Brian Mayer ¹, James Lewicki ¹, Peter Pauzauskie ², Juergen Biener ¹, Joe Satcher ¹, Theodore Baumann ¹
¹Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States, ²Department of Materials Science and Engineering, Unversity of Washington, Seattle, Washington, United States

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3:45 PM - Y2:

BREAK

4:00 PM - **Y2.4

Two-dimensional Layered Chalcogenide Nanoribbons: Energy and Topological Insulators.

Yi Cui ¹
¹Materials Science and Engineering, Stanford University, Stanford, California, United States

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4:30 PM - **Y2.5

Carbon Materials Nanofabrication via Graphene Self-assembly.

Sang Ouk Kim ¹
¹, KAIST, Daejeon Korea (the Republic of)

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The organization of carbon materials, especially planar and mechanically flexible graphene, into complex three-dimensional geometries is a major challenge for their ultimate utilization in various applications. In this presentation, our recent research achievements of graphene assembly into three-dimensional functional architectures will be introduced [1]. In the first approach, reduced graphene films with nanoscale thickness assembled from graphene oxide aqueous solution, has been utilized for the substrate material for vertical carbon nanotubes growth [2-4]. The resultant mechanically flexible and electro-conductive carbon nanotubes-graphene hybrid architecture is potentially useful for electrodes of flexible display or energy storage. In the second approach, Polymer-grafted graphene oxide was assembled into macroporous films by self-organized aqueous droplets [5]. Subsequent pyrolysis yielded mechanically flexible carbon films that exhibited highly ordered morphologies. Incorporation of a nitrogen-doping into the aforementioned protocols enhanced the electrical properties and supercapacitor performances of the carbon-based assemblies, and provided chemical functionality for further chemical derivatization.------------------------------1. S. H. Lee, D. H. Lee, W. J. Lee, S. O. Kim ‘Tailored Assembly of Carbon Nanotubes and Graphene’ Adv. Funct. Mater. (invited feature article).2. D. H. Lee, J. E. Kim, T. H. Han, J. W. Hwang, S. W. Jeon, S.-Y. Choi, S. H. Hong, W. J. Lee, R. S. Ruoff, S. O. Kim ‘Versatile Carbon Hybrid Films Composed of Vertical Carbon Nanotubes Grown on Mechanically Compliant Graphene Films’ Adv. Mater. 22, 1247 (2010).3. B. H. Kim, J. Y. Kim, S. -J. Jeong, J. O. Hwang, D. H. Lee, D. O. Shin, S. Y. Choi, S. O. Kim ‘Surface Energy Modification by Spin Cast, Large Area Graphene Film for Block Copolymer Lithography’ ACS Nano 4, 5464 (2010).4. D. H. Lee, J. A. Lee, W. J. Lee, S. O. Kim ‘Flexible Field Emission of Nitrogen-Doped Carbon Nanotubes/Reduced Graphene Hybrid Films’ Small inpress.5. S. H. Lee, H. W. Kim, J. O. Hwang, W. J. Lee, J. Kwon, C. W. Bielawski, R. S. Ruoff, S. O. Kim ‘Three-Dimensional Self-Assembly of Graphene Oxide Platelets into Mechanically Flexible Macroporous Carbon Films’ Angew. Chem. Int. Ed. inpress.

5:00 PM - Y2.6

Self-aligned Graphene Sheets-polyurethane Nanocomposites.

Mohsen Moazzami Gudarzi ¹, Seyed Hamed Aboutalebi ¹, Qing Bin Zheng ¹, Jang-Kyo Kim ¹
¹Mechanical Engineering, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon Hong Kong

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5:15 PM - Y2.7

Solution-processed Graphene/MnO2 Composite Nanostructures for Electrochemical Capacitors.

Guihua Yu ¹, Liangbing Hu ², Michael Vosgueritchian ¹, Yi Cui ², Zhenan Bao ¹
¹Chemical Engineering, Stanford University, Stanford, California, United States, ²Materials Science and Engineering, Stanford University, Stanford, California, United States

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5:30 PM - Y2.8

Tailoring the Atomic and Electronic Structure of Two-dimensional Carbon and Boron-nitride Systems with Electron and Ion Beams.

Arkady Krasheninnikov ^{1 2}
¹Department of Physics, University of Helsinki, Helsinki Finland, ²Department of Applied Physics, Aalto University, Espoo Finland

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2011-04-27 Show All Abstracts

Symposium Organizers

AlexanderA. Balandin University of California-Riverside

Andre Geim University of Manchester

Jiaxing Huang Northwestern University

Dan Li Monash University

Symposium Support

Cambridge NanoTech Inc

Elsevier Ltd.

Y5: Characterization and Properties of Graphene I

Session Chairs

Alexander Balandin

Vincent Tung

Wednesday AM, April 27, 2011

Room 3009 (Moscone West)

11:30 AM - **Y5.1

Atomically Controlled Graphene and Hexa Boron Nitride Layer Sstack for Advanced Electronics.

Philip Kim ¹
¹Physics, Columbia University, New York, New York, United States

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12:00 PM - **Y5.2

Making Nanographene.

Kian Loh ¹, Jiong Lu ¹
¹Department of Chemistry, National University of Singapore, Singapore Singapore

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12:30 PM - Y5.3

Transport Properties of Graphene on SiO₂ with Gpecific Surface Structures.

Kosuke Nagashio ¹, Takaaki Yamashita ¹, Tomonori Nishimura ¹, Koji Kita ¹, Akira Toriumi ¹
¹Materials Engineering, The University of Tokyo, Bunkyo-ku, Tokyo, Japan

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Mobility of graphene transferred on the SiO₂/Si substrate is limited to ~10,000 cm²/Vs. Without understanding the interaction between graphene and SiO₂, it is difficult to improve transport properties. Although several surface structures for SiO₂ such as OH-termination and O-termination are recognized, the relation between the surface treatment of SiO₂ and graphene characteristics has not been elucidated yet in spite of its importance. This paper discusses the electrical transport properties of graphene on specific surface structures of SiO₂ prepared by plasma treatments and reoxidization. OH-terminated and O-terminated SiO₂ surfaces were prepared by O₂-plasma treatment and reoxidization at 1000 °C for 5 min. in 100%-oxygen gas flow, respectively. The hydrophilic properties of these SiO₂ surfaces were studied by the contact angle measurement. The contact angles of droplets on plasma-treated SiO₂ decreases from ~6° for untreated SiO₂ (HF-last) to nearly zero, indicating that the hydrophilic nature is enhanced due to the increase in OH groups with the strong polarization by removing hydrocarbon contaminants on untreated SiO₂. On the other hand, the reoxidized SiO₂ was hydrophobic (42.6°) because of O-termination with the weak polarization. Graphene was transferred on surface-treated SiO₂ by the mechanical exfoliation of Kish graphite and, then, typical 4-probe FET devices were fabricated by the conventional EB lithographic technique. The mobility of graphene on OH-terminated SiO₂ was much lower than those on untreated SiO₂ and Dirac point considerably deviated positively from VG=0. The polarized OH group of 4~5×10¹⁴ cm^-2 on the SiO₂ surface might interact strongly with graphene and work as scattering centers. Therefore, it is reasonable that the Coulomb interaction results in the considerable mobility degradation and large Dirac point shift. For untreated SiO₂, on the other hand, the hydrocarbon does exist, which separates graphene from OH groups, that is, the weak interaction. Therefore, Dirac point stayed at V_G=~0. Moreover, the mobility and Dirac point shift of graphene on O-terminated SiO₂ were very similar to untreated SiO₂, while the hysteresis was considerably reduced because of hydrophobic nature. Finally, it should be pointed out that “ideal” SiO₂ surface structure is defined as O-termination only at high temperature since the surface is constructed only by constituent atoms of Si and O. The surface structure of untreated SiO₂ (HF-last) is not intrinsic due to the existence of hydrocarbons. Although full OH-termination by O₂-plasma treatment seems to be intrinsic in terms of uniformity, it is very active to the environment and attracts water, hydrocarbons and so on. In terms of the stability to the environment, O-terminated SiO₂ seems to be best due to hydrophobic nature.

12:45 PM - Y5.4

Influence of Chemical Functionalization on the Electron Transport in Graphene.

Fabian Koehler ¹, Arnhild Jacobsen ², Klaus Ensslin ², Wendelin Stark ¹
¹Institute for Chemical and Bioengeneering, ETH Zurich, Zurich Switzerland, ²Solid State Physics Laboratory, ETH Zurich, Zurich Switzerland

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Chemical functionalization of graphene with organic molecules extends the available derivatization methods, namely oxidation of graphene to graphite oxide and hydrogenation of graphene to graphane. Instead of oxygen or hydrogen a carbon atom is attached to the graphene lattice. Previous studies(1,2) showed the potential for the modification of single and bilayer graphene by reaction with diazonium reagents. A combination of Atomic force microscopy and confocal Raman spectroscopy are used to characterize the chemically introduced changes (sp2 to sp3) of the graphene carbon atoms. A clear difference is seen in the reactivities on single and double layer graphene. Surprisingly, the reaction rate is enhanced at the graphene edge regions due to a lower steric hindrance and activation energy. These edge regions grow into the bulk graphene areas, like a domino effect. In a second aspect(3) the influence of water and solvents, used in the reaction step, are investigated. These show a dramatic effect on the Dirac point and mobility of graphene, which is probably due to the removal of residues or dopants. Furthermore, we have performed a transport study of chemically modified graphene and found that the influence of isopropanol treatment is comparable to the influence of functionalization itself. It is shown that isopropanol leads to p-doping similar to that observed after functionalization. In addition, it is observed that isopropanol treatment followed by heating significantly improves the electronic quality of graphene beyond the improvement due to heating alone. In conclusion, this may lead to a better understanding of how organic molecules interact with graphene and influence its electron transport. [1] F.M. Koehler, N.A. Luechinger, D. Ziegler, E.K. Athanassiou, R.N. Grass, A. Rossi, C. Hierold, A. Stemmer, W.J. Stark, Angew. Chem. Int. Ed., 2009, 48, 224[2] F.M.Koehler, A. Jacobsen, K. Ensslin, C. Stampfer, W.J. Stark, Small, 2010, 6(10), 1125[3] A. Jacobsen, F.M. Koehler, W.J. Stark, K. Ensslin, NJP, 2010, accepted

Y6: Characterization and Properties of Graphene II

Session Chairs

Andrea Ferrari

Lain-Jong (Lance) Li

Wednesday PM, April 27, 2011

Room 3009 (Moscone West)

2:30 PM - **Y6.1

Exploiting Graphene Optoelectrionic Properties in Photonic Devices and Novel Characterisation Tools.

Andrea Ferrari ¹
¹, University of Cambridge, Cambridge United Kingdom

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3:00 PM - Y6.2

Rapid Large-Scale Characterization of CVD Graphene Layers on Glass Using Fluorescence Quenching Microscopy.

Jennifer Reiber Kyle ¹, Ali Guvenc ¹, Maziar Ghazinejad ², Jian Lin ², Cengiz Ozkan ², Mihrimah Ozkan ¹
¹Electrical Engineering, University of California Riverside, Riverside, California, United States, ²Mechanical Engineering, University of California Riverside, Riverside, California, United States

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Graphene is a two-dimensional sheet of carbon atoms arranged in hexagonal lattices. Graphene exhibits exceptional electrical, optical, and mechanical properties which has generated a great interest in the material. At first, graphene was fabricated by mechanical exfoliation of highly ordered graphite. However, due to the small size limitation of exfoliated graphene, a new method for fabricating graphene, known as chemical vapor deposition (CVD), was developed. CVD-grown graphene is not limited in size but is subject to quality concerns due to growing conditions that have yet to be optimized. Two important parameters in the performance and properties of graphene are the number of layers and uniformity throughout the sample. In this research project we measure the thickness and uniformity of large CVD-grown graphene samples on microscope glass slides using fluorescence quenching microscopy (FQM). FQM is a novel technique for visualizing graphene that is based on the discovery that graphene quenches fluorescence via resonant energy transfer. FQM offers improvements over alternative graphene imaging techniques such as atomic force microscopy, Raman spectroscopy, transmission electron microscopy, and optical reflection and transmission techniques because it can be performed on arbitrary substrates, imaging time is short, large areas can be measured, and the imaging equipment (a fluorescent microscope) is widely available. Currently, FQM has only been used to visualize graphene-oxide and exfoliated graphene samples and has been unable to achieve quantitative characterization of the graphene samples, specifically, counting graphene layers. FQM is achieved by spin-coating a solution of polymer mixed with a fluorescent dye onto the graphene layer. In this work, we calibrate the fluorescent quenching by the graphene layers, measuring the contrast between the graphene and background for dye layers of different thickness. As the dye layer thickness decreases, the contrast between graphene and the substrate increases, but the contrast between graphene layers decreases. Using the results from our fluorescence quenching calibration, we quantify the thickness and uniformity of an entire CVD-grown sample. This is achieved by creating a large-scale, high-resolution fluorescence montage image of the entire graphene sample using a microscope with a motorized stage. We segment the image based on graphene layer thickness using histogram-based segmentation and calculate the mean thickness and RMS roughness of the graphene sample. This work introduces a new method for graphene quantification that can quickly and easily identify graphene layers in a large area on arbitrary substrates.

3:15 PM - Y6.3

Nanoscale Mapping of Bulk and Interface Elastic and Related Physical Properties of Layered Materials Using Scanning Force Microscopy at Ultrasonic Frequencies.

Oleg Kolosov ¹, Manuel Pumarol ¹, Peter Tovee ¹, Vladimir Falko ¹, Franco Dinelli ²
¹Physics, Lancaster University, Lancaster United Kingdom, ², CNR-INO, Pisa Italy

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We report new scanning probe microscopy approach for the investigation of nanoscale physical properties of two-dimensional materials. It is hard to overestimate the importance of such properties as local elastic moduli, interface adhesion, thermal expansion coefficient, and in-plane, out-of-plane and layer-to-substrate thermal conductivity for the exploration of physical nature of 2D materials as well influence of these properties on the performance of related devices.In order to realise such measurements, we combined atomic force microscope (AFM) that is known to have required nanometre scale resolution, with the ultrasonic excitation of the sample or force sensitive cantilever at high frequencies (HF) ranging from few MHz to hundreds MHz. A first combination, known as Ultrasonic Force Microscope (UFM), uses an excitation of only the sample or the cantilever and was shown to be directly sensing nanoscale mechanical properties of materials including ones of stiff ceramics and ceramic based composites. The Heterodyne Force Microscopy (HFM), where two HF vibrations at adjacent frequencies are detected by the nonlinearity of tip-surface contact, is shown in addition to be sensitive to the time dynamics of these interactions. In addition, both UFM and HFM were shown to reveal the mechanical properties of the interfaces and subsurface delaminations.In this paper, we report novel experimental results of imaging of thin graphene layers ranging from a single graphene sheet to few tens of graphene layers. UFM revealed variability of adhesion of graphene layers to the substrate on the lateral scale of few tens of nanometres (in the flat sheet), and few nm (near the edge of the sheet). The contact elasticity of layer-on-substrate was shown to consistently decrease with the increase of layer thickness between one to four graphene layers, as well as to change a character of delaminations between layer and substrate. In addition, UFM and HFM studies of folded layers showed variability of the intimate elastic contact between layers revealing the nanomechanics of such folding. We also observed a correlation between mechanical and thermal transport properties in two-dimensional structures by using a scanning thermal microscopy of such layered materials as graphene and mica with the thermal resolution on the scale of few tens of nm. Finally, we compare these data with the finite elements simulation of heat conductance of two dimensional materials on the substrate.A. Briggs and O. Kolosov, Acoustic Microscopy, ch. 13, 2nd edition, Oxford University Press, 2010.

3:30 PM - Y6.4

Sub-100 nm Spatial Resolution Imaging of Conductance Inhomogeneities in CVD Graphene.

Alexander Tselev ¹, Nikolay Lavrik ¹, Ivan Vlassiouk ¹, Sergei Kalinin ¹
¹, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States

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Continued interest in graphene is due to its unique atomic structure as well as remarkable mechanical, optical, thermal, and electronic properties. In particular, graphene has attracted substantial attention due to its potential applications in photovoltaics and in energy storage systems. Among many properties of graphene, high electrical conductivity is of primary importance for these applications. From this standpoint, there is a trade-off between more challenging technological approaches that yield in a nearly perfect graphene and those that are more suitable for large-scale fabrication. Growth of large-area graphene on polycrystalline catalytic surfaces using chemical vapor deposition (CVD) is compatible with wafer level fabrication and can readily be scaled up. However, CVD-grown graphene is not always characterized by the high degree of structural perfection and tends to exhibit lower electron mobility and electrical conductivity. This points to an ultimate importance of characterization and mapping of local conductivity of various graphene samples with nanoscale lateral resolution. In this work, we demonstrate that local conductivity in continuous large-area graphene layers can be imaged with a spatial resolution of better than 100 nm using near-field scanning microwave microscopy (SMM). The important feature of the SMM technique is that it does not require deposition of metal contacts to access the local conductivity in contrast to conducting AFM. Due to a relatively high frequency used—about 2 GHz—the electric current path is complete by displacement currents due to capacitive coupling between the sample, probe tip, and the probe shield electrode. To make the system sensitive to local properties of the graphene film, rather than to its overall capacitance in respect to the conducting substrate and the microwave circuit ground, we cover the whole sample with a layer of alumina of about 4 nm thickness using Atomic Layer Deposition. These thickness provides a pinhole-free film insuring a strong enough capacitive coupling between the probe tip and the graphene film. Alumina can be readily removed by a mild chemical etching using a standard recipe. Research at ORNL's CNMS was sponsored by the Scientific User Facilities Division, BES, U.S. DOE. I.V. acknowledges a Eugene P. Wigner fellowship from the ORNL.

3:45 PM - Y6.5

Direct Atomic-Scale Structural Characterization of Epitaxial Graphene on 6H-SiC(0001) by Cross-sectional Scanning Transmission Electron Microscopy.

Xiaojun Weng ¹, Joshua Robinson ^{2 3}, Kathleen Trumbull ², Randall Cavalero ², Mark Fanton ², David Snyder ^{2 4}
¹Materials Research Institute, Penn State University, University Park, Pennsylvania, United States, ²Electro-Optics Center, Penn State University, University Park, Pennsylvania, United States, ³Materials Science and Engineering, Penn State University, University Park, Pennsylvania, United States, ⁴Chemical Engineering, Penn State University, University Park, Pennsylvania, United States

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The interface layer between the epitaxial graphene (EG) and the SiC substrate significantly affects the epitaxial growth and the electronic properties of the EG [1]. It is thus critical to obtain an explicit understanding of the structure and chemistry of the interface layer in order to understand the EG growth mechanism and eventually produce EG layers with desired thickness uniformity and electronic properties. However, the nature of the interface layer is still elusive to date. Other structural properties of EG, e.g. layer spacings and the atomic structure of surface steps, also remain to be ambiguous.Most of the current knowledge of the structure of the interface layer, interlayer spacings, and the thickness and the surface steps of graphene layers in EG/SiC(0001) was either from theoretical studies, or derived from experimental measurements such as plan-view scanning tunneling microscopy, low-energy electron diffraction/microscopy, angle-resolved photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy (TEM). These experimental methods require complicated data analysis or image simulation in order to obtain accurate structural information of EG/SiC. Here, we report the atomic-scale structural properties of EG with 1 to 4 layers on SiC(0001) obtained from directly interpretable cross-sectional high-angle annular-dark-field (HAADF) scanning TEM (STEM).We find that the interface layer between the EG and the SiC substrate possesses a relatively weaker contrast than the other EG layers in STEM images, indicating that it possesses a lower areal density of C atoms than a graphene monolayer. This is in contradiction with the assertion from several recent reports that the interface layer was a graphene-like sheet with the 6√3×6√3R30° structure. Direct measurements of the layer spacings revealed that the EG interlayer spacing was considerably larger than that of bulk graphite. Interestingly, the spacing between the interface layer and the top bilayer of the SiC substrate apparently increased with the EG layer thickness. The surface of the SiC(0001) substrate, often treated as relaxed, was found to be strained. The strain may be due to the point defects induced by the partial decomposition of the surface layers. We find that the top two layers of a 4-layer EG terminated at the step instead of growing continuously. This observation contradicts the commonly believed carpet-like growth mode for the EG layers as determined by other experimental techniques, in which the top EG layers grow continuously over the surface steps of the SiC substrates. We believe that these results provide fundamental structural information for the better understanding of the relationship between the structure and electronic properties, as well as for the theoretical predictions of the electronic properties of EG layers on SiC(0001). [1] J. Hass, W.A. de Heer, and E.H. Conrad, J. Phys.: Condens. Matter 20 (2008) 323202.

4:00 PM - Y6

BREAK

4:30 PM - **Y6.6

Nearly Free Electron States in Graphene Nanoribbon Superlattices.

Jinlong Yang ¹
¹Dept. of Chem. Phys., Univ. of Sci. & Tech. of China, Hefei, Anhui, China

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5:00 PM - Y6.7

Low-frequency Noise of Graphene Nanostructures for Device and Material Characterizations.

Guangyu Xu ¹, Carlos Torres Jr. ¹, Jingwei Bai ², Emil Song ¹, Xiangfeng Duan ³, Yuegang Zhang ⁴, Kang Wang ¹
¹Electrical Engineering, University of California, Los Angeles, Los Angeles, California, United States, ²Material Science and Engineering, University of California, Los Angeles, Los Angeles, California, United States, ³Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, United States, ⁴Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States

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Graphene is a two-dimensional atomically-thin film with great potential in diverse applications. However, most non-suspended graphene sheets can be degraded by external perturbations from the environment. For example, the charged impurity lowers the carrier mobility of graphene devices and creates an inhomogeneous charge distribution along the graphene sheet; the trap-induced carrier switching process near the graphene-substrate interface leads to device variability, which has been broadly characterized using low-frequency (1/f) noise. Study on the 1/f noise behavior of substrated graphene would help to understand and realize high-speed graphene electronics with high signal-to-noise-ratios. It would be also of fundamental interest to investigate how the presence of spatial charge inhomogeneity influences the 1/f noise behavior in graphene. We conduct the low frequency noise measurement of SiO₂-substrated single-layer and bi-layer graphene (SLG/BLG)¹, whose gate dependence of graphene, M-shape for SLG and V-shape for BLG, exhibits strong correlation with the spatial charge inhomogeneity. A new noise model has been set for understanding these noise behaviors in graphene. Taking a step further, we also analyzed the noise behavior in nanowire-patterned graphene nanoribbons (GNRs)², which is advantageous over the wide graphene sheets for switching on/off the devices in the presence of an energy gap. We observe a strong correlation between the enhanced conductance fluctuations (noise) of GNR and its quasi-one-dimensional electronic band structure at 77K. This correlation provides a robust mechanism to directly probe the band structure of GNRs, especially when the subband feature is smeared out in conductance measurement. Our result can further extend to a broad range of low-dimensional nano-materials and promote the noise-based metrology for the electronic band structure of quantum transport systems. The low-frequency noise thus proves its great potential in both the device and material characterization for graphene electronics. 1. G. Xu et. al. Nano Lett. 10, 3312-3317 (2010);2. G. Xu et. al. Nano Lett. 10.1021/nl1025979, ASAP (2010)

5:15 PM - Y6.8

Force Field Spectroscopy of the h-BN Nanomesh on Rh(111).

Thilo Glatzel ¹, Sascha Koch ¹, Markus Langer ¹, Shigeki Kawai ¹, Jorge Lobo-Checa ³, Thomas Brugger ², Thomas Greber ², Ernst Meyer ¹
¹Department of Physics, University of Basel, Basel Switzerland, ³Centre d'Investigaciò en Nanociència i Nanotecnologia (CIN2), Campus Universitat Autònoma de Barcelona, Barcelona Spain, ²Department of Physics, University of Zürich, Zürich Switzerland

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5:30 PM - Y6.9

Imaging and Spectroscopy of Chemical and Structural Defects in Single-layer Materials.

Matthew Chisholm ¹, Veena Krishnan ², Gerd Duscher ^{2 1}, Wolfgang Windl ³
¹Materials Science and Technology, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, ²Materials Science and Engineering Department, University of Tennessee, Knoxville, Tennessee, United States, ³Materials Science and Engineering Department, The Ohio State University, Columbus, Ohio, United States

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2011-04-28 Show All Abstracts

Symposium Organizers

AlexanderA. Balandin University of California-Riverside

Andre Geim University of Manchester

Jiaxing Huang Northwestern University

Dan Li Monash University

Symposium Support

Cambridge NanoTech Inc

Elsevier Ltd.

Y10: Poster Session II

Session Chairs

Alexander Balandin

Jiaxing Huang

Dan Li

Thursday PM, April 28, 2011

Salons 7-9 (Marriott)

1:00 AM - Y10: Poster2

Y10.4 Transferred to Y7.5

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Y7: Characterization and Properties of Graphene III

Session Chairs

Dal Hee Min

Michael Shur

Thursday PM, April 28, 2011

Room 3009 (Moscone West)

9:15 AM - **Y7.1

New Developments in Synthesis and Characterization of Graphene and Layered Boron Nitride.

Alex Zettl ¹
¹, University of California at Berkeley, Berkeley, California, United States

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9:45 AM - Y7.2

Anomalous Strength Characteristics of Tilt Grain Boundaries in Graphene.

Vivek Shenoy ¹
¹, Brown University, Providence, Rhode Island, United States

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10:00 AM - Y7.3

In situ High-temperature Scanning Tunneling Microscopy Studies of Epitaxial Graphene Growth on SiC(0001).

Yuya Murata ¹, Vania Petrova ², Ivan Petrov ², Suneel Kodambaka ¹
¹Materials Science and Engineering, University of California Los Angeles, Los Angeles, California, United States, ²Frederick-Seitz Materials Research Laboratory, University of Illinois, Urbana, Illinois, United States

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10:15 AM - Y7.4

In-situ Analysis of Graphene Growth Process on Magnetic Metal Thin Films.

Shiro Entani ¹, Yoshihiro Matsumoto ¹, Pavel Avramov ¹, Hiroshi Naramoto ¹, Seiji Sakai ¹
¹, Japan Atomic Energy Agency, Tokai Japan

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10:30 AM - Y7.5

Wrinkles and Overlaps: Structure-property Relationships of Graphene Oxide Monolayers.

Laura Cote ¹, Jaemyung Kim ¹, Zhen Zhang ², Cheng Sun ², Jiaxing Huang ¹
¹Materials Science, Northwestern University, Evanston, Illinois, United States, ²Mechanical Engineering , Northwestern University, Evanston, Illinois, United States

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10:45 AM - Y7: Charact

BREAK

Y8: Applications of Graphene I

Session Chairs

Dal Hee Min

Michael Shur

Thursday PM, April 28, 2011

Room 3009 (Moscone West)

11:15 AM - **Y8.1

Large Scale Production of 2D Atomic Crystals by Liquid Phase Exfoliation of Layered Materials.

Jonathan Coleman ¹, Valeria Nicolosi ², Mustafa Lotya ¹, Arlene O'Neill ¹, Shane Bergin ¹, Paul King ¹, Umar Khan ¹, Karen Young ¹, Sukanta De ¹, Ronan Smith ¹, Gregory Moriarty ³, Jaime Grunlan ³
¹, Trinity College Dublin, Dublin Ireland, ², University of Oxford, Oxford United Kingdom, ³, Texas A&M University, College Station, Texas, United States

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11:45 AM - Y8.2

Material Choices For Haptic Interfaces.

Paul Beecher ¹, Piers Andrew ¹, Zoran Radivojevic ¹, Chris Bower ¹, Samiul Haque ¹, Andrea Ferrari ², Tawfique Hasan ², Francesco Bonaccorso ²
¹, Nokia Research Center, Cambridge United Kingdom, ²Engineering, University of Cambridge, Cambridge United Kingdom

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We present a robust, thin and optically transparent interface structure that can be overlaid unobtrusively on top of a display screen. This structure acts as an electrotactile system that directly delivers localized and visually correlated tactile information to the user’s skin, enabling graphic tactile feedback. The device structure operates at very low current level (< 10µA) and with potentials in the range of tens of volts, which is a significant improvement on current electrotactile paradigms. The proposed structure doubles as an input and output device in assisting the user interaction with a touch screen display.The technology is based on electrovibration, in which touch receptors in the skin can be deceived into perceiving texture when a fingertip is swiped across an insulating layer above a metal surface carrying an alternating potential. This effect is due to the varying electrostatic attraction between the conductor and the deeper, liquid-rich conducting layers of the skin – an effect which changes the perceived dynamic friction. Complex stimulation patterns, involving the mixing of multiple AC frequency components (10Hz – 500Hz) and the actuation of several electrodes simultaneously, may allow for the generation of an unprecedented range of “haptic illusions”. These may range from the emulation of real touch sensations, to completely new patterns of tactile feedback, and new ways of interacting with electronic devices. This solution also overcomes the need for the physical displacement of mechanical parts and is therefore several orders-of-magnitude more energetically efficient in providing real time feedback to the user.Our work tackles the expected evolution of mobile devices and displays towards flexible and compliant form factors. Our concept implementation is based on the use of novel nanomaterials and structures that are compatible with the requirements for these new technologies. Conductors that are simultaneously flexible, conductive and transparent have been investigated, ranging from wide-bandgap oxide materials to carbon nanostructures, e.g., carbon nanotube networks and graphene, and also include silver nanowire networks and thin metal grids. These conductors can all be deposited on flexible substrates, and uniformly coated with appropriate dielectric materials. Much focus has been on high-k amorphous oxide materials such as hafnia, but, barium titanate and parylene have also been used. The exploration of an extensive materials library necessitates use of a number different fabrication techniques including sputtering, vacuum deposition, and various solution methods and printing techniques. In addition, the inclusion of scratch resistant, hydrophobic and oleophobic materials on the top surface to combine electrical insulation, scratch resistance and stain/water/fingerprint repellence in a single finishing layer helps maintain and protect a pristine display surface.

12:00 PM - Y8.3

Graphene-based Platforms for Bioanalysis of Enzyme Activities.

Dal-Hee Min ¹
¹, KAIST, Daejeon Korea (the Republic of)

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12:15 PM - Y8.4

Nanoscale Friction and Adhesion Behavior of Atomically-thin Two-dimensional Materials.

Robert Carpick ¹, Xin-Zhou Liu ¹, Qunyang Li ¹, Baolei Zhang ¹, Zhengtang Luo ¹, Luke Somers ¹, Andrew Konicek ², Changgu Lee ³, Ji Feng ¹, J. Li ¹, A. T. (Charlie) Johnson ¹, James Hone ⁴
¹Mechanical Engineering & Applied Mechanics Department, University of Pennsylvania, Philadelphia, Pennsylvania, United States, ², Columbia University, New York, New York, United States, ³, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, ⁴, Sungkyunkwan University, Gyeonggi Korea (the Republic of)

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The remarkable characteristics of two-dimensional (2D) materials not only include physical, chemical, electronic, and optical properties but also extends to their mechanical and frictional (tribological) behavior. We have used friction force microcopy (FFM) to study atomic-scale friction between FFM tips and several 2D materials, down to the level of single atomic sheets1. For mechanically exfoliated samples of graphene, MoS2, NbSe2, and hexagonal BN weakly bound to supporting substrates, we observe atomic scale stick-slip friction that diverges from bulk behavior as the limit of single atomic sheets is approached. Specifically, while frictional energy dissipation is low compared to bare Si and many other common materials, friction increases substantially for fewer layers, with single layers exhibiting roughly 50% higher friction than their thick counterparts. Moreover, the friction force required to slip increases with sliding distance for the first few nanometers of scanning, but then saturates. This unusual layer-dependence of friction is suppressed by exfoliating on to highly adherent substrates. The details revealed by the atomic-scale friction measurements coupled with finite element modeling (FEM) and molecular dynamics simulations indicate that the trend arises from the thinner sheets’ increased susceptibility to out-of-plane elastic deformation. However, measurements of adhesion between nanoscale tips and few-layered graphene reveal that the adhesion does not change appreciably for different layer numbers, consistent with the weak dependence of adhesion on thickness predicted by the FEM simulations. We will discuss the mechanism accounting for this behavior, which, based on preliminary measurements, is rooted in the need to develop deformations of the sheets that is dependent on the scanning history. We have also investigated the mechanical and chemical properties of chemically exfoliated graphene oxide (GO). FFM was used to determine the friction between Si tips and GO samples. Unlike the other 2-D materials, no strong dependence of friction on thickness was observed. We will discuss the distinct behavior of GO with reference to the enhanced chemical interaction of GO with the silicon oxide substrate. An enhancement of friction and adhesion with respect to graphene is observed, suggesting that oxidation of graphene is an effective route for tailoring nanoscale friction and adhesion. The chemical properties of GO are further examined by near edge x-ray absorption fine structure spectroscopy experiments. 1. C. Lee, Q. Li, W. Kalb, X.-Z. Liu, H. Berger, R.W. Carpick & J. Hone, Frictional characteristics of atomically-thin sheets. Science 328, 76-80 (2010).

12:30 PM - Y8.5

Gas Phase Electronic Sensing Using DNA-coated Graphene Field Effect Transistors.

Ye Lu ¹, Brett Goldsmith ¹, Nicholas Kybert ¹, A.T.Charlie Johnson ¹
¹Physics, University of Pennsylvania, Phl, Pennsylvania, United States

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12:45 PM - Y8.6

Study of Plasmon Excitation in Graphene.

Long Ju ¹, Baisong Geng ¹, Jason Horng ¹, Caglar Girit ¹, Micahel Martin ¹, Zhao Hao ^{2 3}, Hans Bechtel ², Xiaogan Liang ⁴, Alex Zettl ^{1 5}, Y. Ron Shen ^{1 5}, Feng Wang ^{1 5}
¹Department of Physics, University of California at Berkeley, Berkeley, California, United States, ²Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, ³Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, ⁴Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California, United States, ⁵Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States

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Y10: Poster Session II

Session Chairs

Alexander Balandin

Jiaxing Huang

Dan Li

Friday AM, April 29, 2011

Salons 7-9 (Marriott)

9:00 PM - Y10.1

Hydrothermally Grown ZnO Nanostructures on Few-layer-graphene Sheets.

Yong-Jin Kim ^{1 2}, Hadi Tukiman ³, Aram Yoon ⁴, Miyoung Kim ⁴, Gyu-Chul Yi ^{1 5}, Chunli Liu ³
¹, Creative Research Initiative Center for Semiconductor Nanorods, Seoul Korea (the Republic of), ²Department of Materials Science and Engineering, POSTECH, Pohang Korea (the Republic of), ³Department of Physics, Hankuk University of Foreign Studies, YongIn Korea (the Republic of), ⁴Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), ⁵Department of Physics and Astronomy, Seoul National University, Seoul Korea (the Republic of)

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The growth of one-dimensional (1-D) semiconductor nanocrystals on graphene layers has attracted much attention because the hybrid nanostructures on graphene layer can be a candidate material system for integrated devices of solid-state electronics and optoelectronics. Graphene has shown a great potential for replacing conventional Si-based electronics due to its high carrier mobility exceeding 10000 cm2/Vs and a high thermal conductivity of 10 kW/m-K. Combined with the excellent electrical and thermal characteristics of graphene layers, graphene-based hybrid 1-D semiconducting nanostructures will provide the diverse and sophisticated device applications. More importantly, recent advances in the large-scale growth of single-layer and few-layer-graphene (FLG) and the transfer of FLG sheets to flexible plastic substrates are promising for stretchable, foldable, and transparent electronics and optoelectronics. However, the growth of 1-D nanostructures has been mostly achieved at high temperature, which is incompatible with flexible and transparent plastic substrates.[1] Compared with high-temperature growth methods, the hydrothermal method is a good candidate for fabricating nanostructures on plastic substrates with FLG sheets. In addition, to fabricate functional components on graphene layers, a facile growth method should be developed to control the dimensions, density, and morphology, as well as to synthesize the nanostructures directly on the FLG sheets without degrading the electrical properties of the graphene.Here, we report on the hydrothermal growth of ZnO nanostructures on FLG sheets with controlled dimensions, density, and morphology. The ZnO nanostructures were directly grown on FLG sheets without seed layer. By changing the hydrothermal growth parameters, including temperature, reagent concentration, and the pH value of the solution, we readily controlled the dimensions, density, and morphology of the ZnO nanostructures. As determined by transmission electron microscopy, single crystalline ZnO nanostructures with c-axis orientation grew vertically on the FLG sheets. Furthermore, high optical quality of ZnO nanostructures on FLG sheets was observed by both photoluminescence and cathodoluminescence spectroscopy. The ability to grow high-quality ZnO nanostructures on FLG sheets at low temperature should greatly increase the versatility and power of these building blocks for stretchable, foldable, and transparent electronics and optoelectronics.References[1] Y.-J. Kim et al., Appl. Phys. Lett. 95, 213101 (2009).

9:00 PM - Y10.10

Pt Deposited Functionalized Graphene Nanosheets/Polypyrrole Composites as a Fuel Cell Catalyst Support.

Burcu Saner ¹, Neylan Gorgulu ¹, Selmiye Alkan-Guersel ¹, Yuda Yueruem ¹
¹Materials Science and Engineering, Sabanci University, Istanbul Turkey

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9:00 PM - Y10.11

Rapid Self-propagating Domino Reactions in Graphite Oxide.

Franklin Kim ¹, Rodolfo Cruz-Silva ³, Jiayan Luo ², Jiaxing Huang ²
¹Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Kyoto Japan, ³Research Center for Exotic Nano Carbon Project, Shinshu University, Nagano Japan, ²Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States

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9:00 PM - Y10.12

The Dynamics of Formation of Graphane-like Fluorinated Graphene Membranes (Fluorographene): A Reactive Molecular Dynamics Study.

Ricardo dos Santos ¹, Pedro Autreto ², Marcelo FLores ², Sergio Legoas ³, Douglas Galvao ²
¹Applied Physics, State University of Campinas, Campinas, Sao Paulo, Brazil, ², Universidade Estadual de Maringa, Maringa, Parana, Brazil, ³Physics, Federal University of Roraima, Boa Vista, Roraima, Brazil

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Graphane is a two-dimensional system consisting of a single layer of fully saturated (sp3 hybridization) carbon atoms [1]. Recently, Elias et al. [2] performed a series of experiments which resulted on the formation of graphane from the graphene membranes under cold plasma exposure. More recently, the experimental realization of fluorographene (graphane-like fluorinated graphene membranes or graphene fluoride) have been reported by different groups [3,4]. In this work we have investigated, using reactive molecular dynamics simulations [5], the dynamics of fluorination of graphene membranes leading to the formation of fluorographene structures. Our results show that the dynamics of formation of flurographene is very similar to the observed to graphane [6], with the main differences being the result of stronger and faster chemical reactivity processes. Fluorographene exhibits the presence of frustrated domains. A frustration is a breaking in the up and down (with relation to the plane defined by carbon atoms) alternating pattern of F atoms. Our results show that a significant percentage of uncorrelated F frustrated domains are formed in the early stages of the fluorination processes leading to membrane shrinkage and extensive corrugations. We have observed that fluorination tends to produce significant defective areas, sometimes with the presence of large holes due to carbon losses. These results suggest that, as in the case of graphanes, large domains of perfect flurographene structures are unlikely to be formed. [1]. J. O. Sofo, A. S. Chaudhari, and G. D. Baker, Phys. Rev. B v75, 153401 (2007).[2] D. C. Elias, R. R. Nair, T. M. G. Mohiuddin, S. V. Morozov, P. Blake, M. P. Halsall, A. C. Ferrari, D. W. Boukhvalov, M. I. Katsnelson, A. K. Geim, K. S. Novoselov., Science v323, 610 (2009).[3] S.-H Cheng et al, Phys. Rev. B v81, 205435 (2010).[4] R. R. Nair et al, arXiv:condmat/1006.3016.[5] A. C. T. van Duin, S. Dasgupta, F. Lorant, and W. A. Goddard III, J. Phys. Chem. A v105, 9396 (2001).[6] M. Z. S. Flores, P. A. S. Autreto, S. B. Legoas and D. S. Galvao, Nanotechnology v20, 465704 (2009); arXiv:condmat/ 0903.0278v1.

9:00 PM - Y10.13

``Graphene-like” Exfoliation of Quasi-2D Crystals of Titanium Ditelluride: A New Route to Charge Density Wave Materials.

Javed Khan ¹, Criag Nolen ¹, Desalehne Teweldebrhan ¹, Roger Lake ¹, Alexander Balandin ¹
¹, UC Riverside, Riverside, California, United States

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