Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session C6: Focus Session: Hexagonal BN, Graphene, and Graphene Oxide Synthesis II |
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Sponsoring Units: DMP Chair: Saikat Talapatra, Southern Illinois University at Carbondale Room: 302 |
Monday, March 18, 2013 2:30PM - 2:42PM |
C6.00001: Growth of Single-Layer Graphene Using Alcohol Catalytic Chemical Vapor Deposition on Cu Substrate Xiao Chen, Pei Zhao, Bo Hou, Erik Einarsson, Shohei Chiashi, Shigeo Maruyama CVD on metal substrates has been proved to be effective in the synthesis of graphene. Compared with commonly used carbon sources methane and ethylene, ethanol is safe and easy to use, thus is advantageous as an alternative graphene growth precursor. Here we report a systematic work of graphene growth on Cu substrate using ethanol precursor. Typically, Cu films were exposed to 100 sccm ethanol flow at 100 Pa and 1000$^{\circ}$C for 20 seconds to yield a continuous single-layer graphene film. Characterization using SEM and Raman spectroscopy indicated that the graphene films were homogeneous and of high quality. We conducted a parametric study to prove that high-quality graphene could be grown when the reaction temperature is 900 to 950$^{\circ}$C and the pressure is lower than 100 Pa. Moreover, graphene growth at lower pressure showed a strong tendency to be self-limiting, resulting in only single-layer graphene even with longer CVD duration (30 min). [Preview Abstract] |
Monday, March 18, 2013 2:42PM - 2:54PM |
C6.00002: Tailoring Graphene Morphology and Orientation on Cu(100), Cu(110), and Cu(111) Robert Jacobberger, Michael Arnold Graphene CVD on Cu is phenomenologically complex, yielding diverse crystal morphologies, such as lobes, dendrites, stars, and hexagons, of various orientations. We present a comprehensive study of the evolution of these morphologies as a function of Cu surface orientation, pressure, H$_{2}$:CH$_{4}$, and nucleation density. Growth was studied on ultra-smooth, epitaxial Cu films inside Cu enclosures to minimize factors that normally complicate growth. With low H$_{2}$:CH$_{4}$, Mullins-Sekerka instabilities propagate to form dendrites, indicating transport limited growth. In LPCVD, the dendrites extend hundreds of microns in the 100, 111, and 110 directions on Cu(100), (110), and (111) and are perturbed by twin boundaries. In APCVD, multiple preferred dendrite orientations exist. With increasing H$_{2}$:CH$_{4}$, the dendritic nature of growth is suppressed. In LPCVD, square, rectangle, and hexagon crystals form on Cu(100), (110) and (111), reflecting the Cu crystallography. In APCVD, the morphology becomes hexagonal on each surface. If given ample time, every growth regime yields high-quality monolayers with D:G Raman ratio \textless 0.1. The understanding gained here provides a framework to rationally tailor the graphene crystal morphology and orientation. [Preview Abstract] |
Monday, March 18, 2013 2:54PM - 3:06PM |
C6.00003: Van der Waals MBE growth of graphene on dielectric substrates Sheng Wang, Ulrich Wurstbauer, Jorge M. Garcia, Lara Fernandes dos Santos, Lei Wang, Antonio Levy, Jungsik Park, Cory R. Dean, Loren N. Pfeiffer, James Hone, Aron Pinczuk Graphene growth on dielectric substrates has potential to enable new kinds of devices and applications. We explore graphene growth by direct deposition of carbon on different dielectric substrates in a MBE environment. Here we consider h-BN and sapphire substrates. The quality of fabricated graphene layers depends on growth conditions such as carbon deposition rate, substrate temperature and total amount of deposited carbon. Characterizations by spatially resolved Raman spectra and AFM images suggest the formation of high quality graphene. On h-BN substrates, single layer growth occurs as nano-domains. On sapphire, large area growth happens with monolayer thickness fluctuations. These results are consistent with a van der Waals growth mode of graphene on dielectric substrates. [Preview Abstract] |
Monday, March 18, 2013 3:06PM - 3:18PM |
C6.00004: Kink kinetics of graphene growth on Ir(111) Paul C. Rogge, Shu Nie, Kevin F. McCarty, Norman C. Bartelt, Oscar D. Dubon Graphene growth of aligned domains on Ir(111) and Ru(0001) is controlled by the attachment of clusters of carbon adatoms. Here we study the growth of rotational variants on Ir(111) and show that the growth is dependent on both cluster attachment and kink kinetics. We simultaneously measure the growth velocity of individual facets and the local concentration of carbon adatoms. The faceted domains tend to lie along the equilibrium zigzag or armchair direction. As the carbon adatom concentration increases, the facets deviate from their equilibrium orientation. This increases the kink density, allowing faster growth. The kink density is a function of the carbon adatom supersaturation. We will discuss how these findings account for the different growth velocities between aligned and rotated domains. This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, of the U.S. Department of Energy Contract No. De-Ac04-94AL85000 (SNL). ODD acknowledges support from the NSF (Grant No. DMR-1105541). PCR acknowledges support from a DoD NDSEG fellowship (32 CFR 168a). [Preview Abstract] |
Monday, March 18, 2013 3:18PM - 3:30PM |
C6.00005: Unoccupied states on Graphene/Cu(111) system Shengmin Zhang, Xuefeng Cui, Cong Wang, Hrvoje Petek Based on the Graphene/Cu(111) system we prepared by the chemical vapor deposition method, we explored the surface states and image potential states by two photon photoemission (2PPE) and angle-resolved photoemission using ultrashort laser pulses. Graphene on the Cu(111) surface can be recognized through 2PPE spectra, based on the theoretical band structure, which showed clear angle dispersions under different wavelength measurements. In addition, the surface state of Cu(111) could also be observed in the 2PPE spectra, and under some certain wavelength, there is a strong resonance of the surface state on Cu(111) and the image potential state on Graphene. With the angle-resolved photoemission, the effective masses of the surface state and image potential state were obtained by simply fitting the dispersion curves. [Preview Abstract] |
Monday, March 18, 2013 3:30PM - 3:42PM |
C6.00006: In situ observation of the graphene domain shape on Ni(111) single crystal films Meifang Li, Jiebing Sun, James Hannon, Rudolf Tromp, Eric Chason Graphene has great potential application in electronics due to its high carrier mobility. Graphene can be grown via chemical vapor deposition (CVD) on many metal surfaces, with Cu and Ni being the most studied. Ni(111) is particularly interesting because graphene is epitaxial and is strongly bound to the substrate. As we show, the epitaxial relationship strongly influences the domain shape. Here we describe in situ LEEM experiments to determine the equilibrium shape of graphene domains grown via dissolution and segregation at elevated temperature. We used a novel ``real space diffraction'' method, coupled with diffracted intensity calculations, to determine the crystallographic orientation of the graphene domains relative to the Ni(111) substrate. We find that the equilibrium shape supports zig-zag edges. However, the domain shape is triangular, rather than hexagonal, indicating that only one type of zig-zag edge is favored. [Preview Abstract] |
Monday, March 18, 2013 3:42PM - 3:54PM |
C6.00007: Electrical Transport Properties of Chemically Reduced Graphene Oxide Thin Films Baleeswaraiah Muchharla, Narayanan Tharangattu Narayanan, Kaushik Balakrishnan, Pulickel Ajayan, Saikat Talapatra We will report on synthesis and electrical characterization of reduced graphene oxide (rGO) obtained from graphene oxide (GO) in ascorbic acid. Electrical transport on thin film devices made from these samples was investigated in a wide range (50 K to 400 K) of temperature. We find that the between the temperature range (150 K to 400 K) these samples show Arrhenius-like temperature dependence. At low temperatures, (50 K to 150 K) variable range hopping (VRH) transport of electrons in a two-dimensional electron system was observed for these samples. The effect of magnetic field on the electrical transport on these materials will presented and discussed. [Preview Abstract] |
Monday, March 18, 2013 3:54PM - 4:06PM |
C6.00008: Electrical Characterization of Graphene Flakes Synthesized Using Liquid Phase Exfoliation of Graphite in Isopropyl Alcohol Saikat Talapatra, Baleeswaraiah Muchharla, Mitchell Connolly, Andrew Winchester, Sujoy Ghosh, Swastik Kar Liquid-phase exfoliation processes for synthesis of nano structures is often a simpler route to get functional nanomaterials in large scale. Here we will report on the synthesis of graphene flakes using exfoliation of bulk graphite in isopropyl alcohol. We will also present electrical characterization of thin film devices made from these exfoliated flakes. Temperature dependence of resistance performed for 10K \textless T \textless 300K shows a slow linear increase in resistance with decrease in temperature. Behavior of thin film devices made from these exfoliated flakes under electrochemical gating environment will be presented and discussed. [Preview Abstract] |
Monday, March 18, 2013 4:06PM - 4:18PM |
C6.00009: Transport properties of high-quality reduced graphene oxide M. Enzelberger, S. Eigler, P. Hoffmann, S. Grimm, A. Hirsch, P. M\"{u}ller Chemical production of graphene, especially reducing graphene oxide has gained a lot of interest in recent years. Yet the transport properties of such materials are usually not compatable to those of graphene. We have found a way to overcome this problem using a modification of the standard Hummer's method. Single flakes of reduced graphene oxide have been investigated. The graphene oxide was deposited onto a SiO$_{2}$/Si substrate and subsequently reduced using hydrogen iodine. The resulting reduced graphene oxide samples were patterned by electron beam lithography. We have characterized the quality of the samples by combining Raman spectroscopy and Hall mobility measurements in magnetic fields up to 14 T and temperatures down to 0.3 K. High-quality samples had a Raman D/G ratio of better than 1 and showed Hall mobilities exceeding 1000 cm$^{2}$/Vs. This is nearly two orders of magnitude higher than what is known for standard reduced graphene oxide. The best samples even show Shubnikov-de Haas oscillations and Hall plateaus. S. Eigler, Christoph Dotzer, Andreas Hirsch, Michael Enzelberger, Paul M\"{u}ller, \textit{Chem. Mater.,}~\textbf{\textit{24}} 1276 (2012) [Preview Abstract] |
Monday, March 18, 2013 4:18PM - 4:30PM |
C6.00010: Probing Charge Migration in Progressively Reduced Graphene Oxide using Electrostatic Force Microscopy Sibel Ebru Yalcin, Charudatta Galande, Hisato Yamaguchi, Gautam Gupta, Pulickel Ajayan, Andrew Dattelbaum, Stephen Doorn, Aditya Mohite The discovery of graphene and tremendous attention it took in the last few years led to the discovery of graphene oxide (GO) for the large scale production of graphene. GO provides an ideal platform to manipulate and control its chemical structure, optoelectronic properties and ionic conductivity for a wide range of applications. Therefore, it is critical to understand the physical and electrical properties of GO that are highly dependent on the density and nature of functional groups. Here, using electrostatic force microscopy (EFM), we inject charge and directly probe the charge migration as the GO is progressively reduced (RGO). EFM results on GO flakes indicate that the injected charge is completely localized within the plane of GO. However, with the increasing degree of reduction, the injected charge rapidly delocalizes over a few microns until it ends up at the edge of the flakes. The results suggest that as we go from GO to RGO, there are more percolating pathways of sp2 that are formed that act as conduits for charge migration. Our results are consistent with the observed photoluminescence quenching on GO flakes measured as a function of reduction from GO to RGO. [Preview Abstract] |
Monday, March 18, 2013 4:30PM - 4:42PM |
C6.00011: ABSTRACT WITHDRAWN |
Monday, March 18, 2013 4:42PM - 4:54PM |
C6.00012: Probing Interfacial Processes on Graphene Surface by Mass Detection Nurbek Kakenov, Coskun Kocabas In this work we studied the mass density of graphene, probed interfacial processes on graphene surface and examined the formation of graphene oxide by mass detection. The graphene layers were synthesized by chemical vapor deposition method on copper foils and transfer-printed on a quartz crystal microbalance (QCM). The mass density of single layer graphene was measured by investigating the mechanical resonance of the QCM. Moreover, we extended the developed technique to probe the binding dynamics of proteins on the surface of graphene, were able to obtain nonspecific binding constant of BSA protein of graphene surface in aqueous solution. The time trace of resonance signal showed that the BSA molecules rapidly saturated by filling the available binding sites on graphene surface. Furthermore, we monitored oxidation of graphene surface under oxygen plasma by tracing the changes of interfacial mass of the graphene controlled by the shifts in Raman spectra. Three regimes were observed the formation of graphene oxide which increases the interfacial mass, the release of carbon dioxide and the removal of small graphene/graphene oxide flakes. [Preview Abstract] |
Monday, March 18, 2013 4:54PM - 5:06PM |
C6.00013: Evolution of Thermally Annealed Graphitic Amorphous Carbon toward Graphene: Structure, Vibrational Dynamics, Electron Emission and Band Gap JR Dennison, Jodie Gillespie, Sterling Smith Standard structural models of graphitic amorphous carbon (g-C)---a ubiquitous form of disordered carbon present in the production of graphenes, nanotubes, fullerenes, diamond films, and graphite---postulate that g-C is composed primarily of sp$^{2}$-bonded nearly planar rafts with a structural distribution of carbon rings with 4 to 8 atoms. An embedded ring approach is used to model vibrational dynamics for planar disordered materials and determine the structural evolution of thermally annealed g-C, based on fits to Raman spectra of g-C annealed to temperatures ranging from 22 $^{\circ}$C to 1050 $^{\circ}$C. This vibrational model assumes that constituent atoms of a material are arranged in n-membered planar rings embedded in the effective medium, a continuous random network of atoms. From the relative intensities of the different frequency peaks resulting from in-plane normal modes, our procedures provide quantitative ring statistics for the structure of g-C. Unannealed g-C is found to have many 5- and 7-membered rings, but the fraction of 6-membered rings increases with annealing temperature consistent with the known result that g-C evolves to nanocrystalline graphite under high T annealing. The structural model is used to explain measurements of the band gap and electron emission of g-C as it is thermally annealed toward a graphene-like structure. [Preview Abstract] |
Monday, March 18, 2013 5:06PM - 5:18PM |
C6.00014: Gold Decorated Graphene for Rapid Dye Reduction and Efficient Electro Catalytic Oxidation of Ethanol R.S. Sai Siddhardha, Lakshman Kumar V, A. Kaniyoor, R. Podila, V.S. Muthu Kumar, K. Venkataramaniah, S. Ramaprabhu, A. Rao, S.S. Ramamurthy A well known disadvantage in fabrication of metal-graphene composite is the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. Here, we demonstrate a novel one pot synthesis of gold nanoparticles (AuNPs) by laser ablation of gold strip and simultaneous decoration of these on functionalized graphene derivatives. Not only the impregnation of AuNPs was linker free, but also the synthesis by itself was surfactant free. This resulted in \textit{in-situ} decoration of pristine AuNPs on functionalized graphene derivatives. These materials were well characterized and tested for catalytic applications pertaining to dye reduction and electrooxidation. The catalytic reduction rates are 1.4 x 10$^{2}$ and 9.4x10$^{2}$ times faster for Rhodamine B and Methylene Blue dyes respectively, compared to earlier reports. The enhanced rate involves synergistic interplay of electronic relay between AuNPs and the dye, also charge transfer between the graphene system and dye. In addition, the onset potential for ethanol oxidation was found to be more negative $\sim$ 100 mV, an indication of its promising application in direct ethanol fuel cells. [Preview Abstract] |
Monday, March 18, 2013 5:18PM - 5:30PM |
C6.00015: Colloidal Stability of Graphene Oxide Nanosheets in Aqueous Solutions Janice Wynn Guikema, Yung-Li Wang, Kai Loon Chen Carbon-based nanomaterials are increasingly used in commercial products as well as in research and industrial applications. Due to its extraordinary properties, graphene has attracted intense research interest and has been demonstrated in many potential applications including solar cells, conductive ink, and transistors. Graphene oxide has also been studied extensively and has been used to produce biocompatible antibacterial paper. Chemical reduction of graphene oxide is commonly used to produce inexpensive graphene in large quantities. With the increasing use of graphene and graphene oxide in consumer products, these nanomaterials may inevitably be released to aqueous systems, resulting in potential risk to environmental ecosystems and human health. The fate and mobility of graphene and its oxides in aquatic systems is dependent on their colloidal stability. We will discuss our study of the early-stage aggregation kinetics of graphene oxide in aqueous solutions. We prepared a suspension of single-layer graphene oxide nanosheets in water and used time-resolved dynamic light scattering to study the influence of electrolytes and pH on the aggregation kinetics of the nanosheets. Atomic force microscopy was employed to further examine the graphene oxide nanosheets. [Preview Abstract] |
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