Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session B8: Focus Session: Hexagonal BN, Graphene, and Graphene Oxide Synthesis I |
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Sponsoring Units: DMP Chair: Mauricio Terrones, Pennsylvania State University Room: 307 |
Monday, March 18, 2013 11:15AM - 11:51AM |
B8.00001: TBD Invited Speaker: Pulickel Ajayan |
Monday, March 18, 2013 11:51AM - 12:03PM |
B8.00002: Molecular beam growth of sub-monolayer and multilayer graphene on h-BN flakes Lara Fernandes dos Santos, Sheng Wang, Ulrich Wurstbauer, Jorge M. Garcia, Lei Wang, Antonio Levy, Jungsik Park, Cory Raymond Dean, Loren N. Pfeiffer, James Hone, Aron Pinczuk We report the successful growth of graphene layers on h-BN substrate flakes in a MBE environment. The growth configuration was designed to allow a gradient in the deposition rate (DR) of carbon on the substrate. The growth conditions such as the substrate temperature were highly controlled. Characterization is carried out by spatially resolved Raman spectroscopy and by AFM imaging. We investigated the graphene coverage on the h-BN flakes. The flakes could be partially covered by a sub-monolayer film, fully covered by a single layer or fully covered by a multilayer film. We find high quality graphene in sub-monolayer and single layer growths. We found a striking independence on the carbon DR, which is attributed to the high mobility of carbons atoms on the h-BN surface. This is a characteristic feature of van der Waals molecular beam growth. [Preview Abstract] |
Monday, March 18, 2013 12:03PM - 12:15PM |
B8.00003: Synthesis and Characterization of Large-Area Graphene Directly CVD-Grown on h-BN Minwoo Kim, Young Jae Song, Min Wang, Seong-Kyu Jang, Sungjoo Lee, Won-Jun Jang, Se-Jong Kahng As an ideal substrate for graphene, hexagonal boron nitride (h-BN) has been utilized and studied extensively by transfer technique, which still has a high chance to have impurities at the graphene/h-BN interface. Here we report direct CVD growth of graphene on large area h-BN film. AFM and Raman spectroscopy measurements show that there is only one monolayer of graphene, and whose unperturbed electronic structures are also confirmed by electron transport measurements and scanning tunneling spectroscopy. High resolution TEM images for cross-section taken before and after transferring graphene/h-BN on to SiO2 indicate this CVD-grown hybrid structure is robust enough. Based on this new method, high quality and large area graphene on h-BN film with a clean interface can be synthesized for the application of electronic devices, and can fill the missing steps to grow fully CVD-grown super-structure of graphene and h-BN. [Preview Abstract] |
Monday, March 18, 2013 12:15PM - 12:27PM |
B8.00004: Initial Growth of h-BN Chanyong hwang, E.K. Seo, Jun Park, Wondong Kim, Inho Lee Recently h-BN has drawn a lot of attention due to its use as an insulating layer for graphene application. Its growth on several transition metal surfaces such as Ni has been focused on their local atomic structure and superstructure formed on surfaces. However, the growth of h-BN in a large has not been studied so far. We found very interesting growth mode of h-BN on Cu surface. The shape of island is strongly dependent on the orientation of the Cu surface, which is quite different from that of the graphene on Cu. Based on the growth model, a fairly large grain size of h-BN(order of 0.1 mm) can be made. More detailed process on the growth of h-BN will be discussed. [Preview Abstract] |
Monday, March 18, 2013 12:27PM - 1:03PM |
B8.00005: In-situ detection of nano-crack of graphene using polarized optical microscopy Invited Speaker: Jong-Hyun Ahn Recent works for producing large-area, high quality graphene films through chemical vapor deposition (CVD) and transferring them onto various large-area substrates have offered the possibility of their use as transparent conductive films in various optoelectronic devices. However, various kinds of defects such as pinhole, nano-crack and grain boundaries incorporated for CVD growth process or transfer process of graphene to target substrates degrade the electrical and mechanical performance, which limit the quality needed for the practical use of graphene films. In particular, knowledge of the mechanism of defect generation in graphene under high strain is important to apply graphene in flexible and stretchable electronic devices. Therefore, various methods have been studied to understand the mechanism of defect generation and observe such defects directly. For example, microscopic tools such as TEM, AFM and STM have a way to observe grain boundaries and defects of graphene. However, these methods have drawbacks such as requirement of a complicated sample preparation, a time delay and limited size of observation. In this talk, we present in situ visualization method to identify the distribution of defects in graphene such as pinhole and crack created by growth and transfer process. In addition, we suggest the alignment of liquid crystal molecules on graphene shows strong correlation with domain size of graphene. [Preview Abstract] |
Monday, March 18, 2013 1:03PM - 1:15PM |
B8.00006: Enhanced catalytic reactivity of graphene and h-BN by selective substitution Junhao Lin, Bin Wang, Sokrates Pantelides Recent experiments have demonstrated that nitrogen-doped graphene is an efficient metal-free catalyst for the oxygen reduction reaction in fuel cells, but the underlying mechanism still needs to be explored. Using first-principles calculations, we find that in N-doped graphene oxygen molecules can only dissociate at carbon atoms surrounded by nitrogen. We attribute the enhanced chemical reactivity of these carbon atoms to the strong localized states near the Fermi level, which results from misalignment of pz orbitals of nitrogen and carbon atoms. We further show that the dissociation of oxygen molecules can also occur in hydrogenated graphene and h-BN based on the same mechanism. Therefore, we propose a generic way for functionalization of graphene to achieve enhanced catalytic reactivity. [Preview Abstract] |
Monday, March 18, 2013 1:15PM - 1:27PM |
B8.00007: CVD graphene growth via magnetic inductive heating of metal substrates Richard Piner, Huifeng Li, Xianghua Kong, Li Tao, Jongho Lee, Deji Akinwande, Rodney Ruoff A new route to the CVD synthesis of graphene with inductive heating of metal substrates is presented. The design and implementation of a new type of reactor that uses magnetic induction to heat metal substrates is presented. The advantages of this reactor and important parameters for the successful growth of high quality graphene or few layer graphene will be presented. Optical and SEM images, Raman spectra, and electron and hole mobility will be presented and compared to results for more traditional CVD methods [Preview Abstract] |
Monday, March 18, 2013 1:27PM - 1:39PM |
B8.00008: Synthesis of Large-grain, Single-crystalline Monolayer and AB-stacking Bilayer Graphene Luyao Zhang, Yung-Chen Lin, Yi Zhang, Han-Wen Chang, Wen-Cheng Yeh, Chongwu Zhou We report the growth of large-grain, single-crystalline monolayer and AB-stacking bilayer graphene by the combination of ambient pressure chemical vapor deposition and low pressure chemical vapor deposition. The shape of the monolayer graphene was modified to be either hexagons or flowers under different growth conditions. The size of the bilayer graphene region was enlarged under ambient pressure growth conditions with low methane concentration. Raman spectra and selected area electron diffraction of individual graphene grain indicated that the each graphene grain is single-crystalline. With electron beam lithography patterned PMMA seeds, graphene nucleation can be controlled and graphene monolayer and bilayer arrays were synthesized on copper foil. Electron backscatter diffraction study revealed that the graphene morphology had little correlation with the crystalline orientation of underlying copper substrate. [Preview Abstract] |
Monday, March 18, 2013 1:39PM - 1:51PM |
B8.00009: CVD growth of large-grain graphene on Cu(111) thin films David L. Miller, Kyle M. Diederichsen, Mark W. Keller Chemical vapor deposition of graphene on polycrystalline Cu foils has produced high quality films with carrier mobility approaching that of exfoliated graphene. Growth on single-crystal films of Cu has received less attention, despite its potential advantages for graphene quality and its importance for eventual applications. This is likely due to the difficulty of obtaining large ($\ge$ 1 mm) grains in Cu thin films, as well as dewetting and roughening of Cu films at temperatures near the Cu melting point (1084 C). We found that 450 nm of Cu(111), epitaxially grown by sputtering onto Al$_2$O$_3$(0001), formed $> 1$ mm grains when annealed at 1065 C for 40 minutes in 40 Torr of Ar and 2.5 mTorr of H$_2$. After this annealing, adding 3 mTorr of CH$_4$ for 8 minutes produced a monolayer graphene film covering $> 99\%$ of the Cu surface. Stopping growth after 4 minutes produced dendritic graphene islands with 6-fold symmetry and diameter of 20 $\mu\textrm{m}$ to 100 $\mu\textrm{m}$. After growth, the Cu film remained smooth except for thermal grooving at grain boundaries and a few holes of diameter $\approx$ 10 $\mu\textrm{m}$ where Cu dewetted completely ($\approx10$ holes on each 5 mm x 6 mm chip). [Preview Abstract] |
Monday, March 18, 2013 1:51PM - 2:03PM |
B8.00010: Drastic reduction in the growth temperature of graphene on Cu substrates via enhanced London dispersion force Jin-Ho Choi, Zhancheng Li, Ping Cui, Xiaodong Fan, Changgan Zeng, Zhenyu Zhang London dispersion force is ubiquitous in nature, and is increasingly recognized to be an important factor in a variety of surface processes. Here we demonstrate unambiguously the decisive role of London dispersion force in non-equilibrium growth of ordered nanostructures on metal substrates using aromatic source molecules. Our first-principles based multi-scale modeling shows that a drastic reduction in the growth temperature, from $\sim$1000 $^{\circ}$C to $\sim$300 $^{\circ}$C, can be achieved in graphene growth on Cu(111) when the typical carbon source of methane is replaced by benzene or p-Terphenyl. The London dispersion force enhances their adsorption energies by about (0.5-1.8) eV, thereby preventing their easy desorption, facilitating dehydrogenation, and promoting graphene growth at much lower temperatures. These quantitative predictions are validated in our experimental tests. The general trends established are also applicable in graphene growth using other aromatic carbon sources, and more broadly in molecular assembly and synthesis of surface-based nanostructures. [Preview Abstract] |
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