Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session W26: Focus Session: Graphene XVI: Functionalization and Growth I |
Hide Abstracts |
Sponsoring Units: DMP Chair: Xiaosong Wu, Georgia Institute of Technology Room: 328 |
Thursday, March 19, 2009 11:15AM - 11:27AM |
W26.00001: Impact of Atomic Hydrogen Adsorption on Transport Properties of Graphene Jyoti Katoch, Jianhao Chen, Masa Ishigami We have measured transport properties of graphene as a function of surface coverage by atomic hydrogen in ultra high vacuum. Hydrogen adsorption is reversible at moderate temperatures and alters electronic properties of graphene at atomic scale. We will discuss dependence of minimum conductivity and field-effect carrier mobility on the density of adsorbed hydrogen. [Preview Abstract] |
Thursday, March 19, 2009 11:27AM - 11:39AM |
W26.00002: Determination of the Crystallographic Orientation of Graphene by Raman Spectroscopy Mingyuan Huang, Hugen Yan, Changyao Chen, Daohua Song, Tony Heinz, James Hone We present a systematic study of the Raman spectra of the G band in graphene monolayers under tunable uniaxial tensile stress. The G band splits into two distinct sub-bands (G$^{+}$, G$^{-})$ because of the strain-induced symmetry breaking. Raman scattering from the G$^{+}$ and G$^{-}$ bands shows a distinctive polarization dependence that reflects the angle between the axis of the stress and the underlying graphene crystal axes. Polarized Raman spectroscopy therefore constitutes a purely optical method for the determination of the crystallographic orientation of graphene. [Preview Abstract] |
Thursday, March 19, 2009 11:39AM - 11:51AM |
W26.00003: Growth and Characterization of CVD Graphene Alfonso Reina, Xiaoting Jia, John Ho, Daniel Nezich, Hyungbin Son, Vladimir Bulovic, Mildred S. Dresselhaus, Jing Kong Large-area ( $\sim $cm$^{2})$ graphene films are grown by ambient pressure chemical vapor deposition (CVD) on evaporated Ni films. We show that proper engineering of the Ni film properties, such as grain structure and surface roughness, and the use of ultra-diluted hydrocarbon flow yield films consisting of 1 to $\sim $10 graphene layers in thickness. Furthermore, the produced graphene can be transferred, by wet-etching the underlying Ni, to a variety of substrates allowing graphene coverage over large areas on different materials such as glass, polymers or other semiconductors. Raman Spectroscopy, electron diffraction and transmission electron microscopy suggest disordered stacking of regions with multilayer graphene. Growth mechanisms will also be discussed. Opto-electronic properties and ambipolar transfer characteristics of the produced material is also demonstrated. [Preview Abstract] |
Thursday, March 19, 2009 11:51AM - 12:03PM |
W26.00004: Chemical exfoliation procedure for graphene deposition Michelle Zimmermann, Mahito Yamamoto, Brad Conrad, Jianhao Chen, Ellen Williams Mechanical exfoliation techniques for graphene production yield flakes which are too small and too rare for feasible large-scale experiments or commercial device fabrication. We present a systematic evaluation of the steps involved in chemical exfoliation of graphite to generate suspended graphene sheets. The approach is based on the solubilizing of a graphite intercalation compound in a polar solvent, analogous to solubilization of CNT salts [1] and recently reported for graphene [2]. A shift in the Raman G peak of graphite provides a metric of the degree of intercalation of lithium and naphthalene into graphite flakes. To optimize deposition onto SiO$_{2}$ substrates, we compare drop casting, spin-coating and dip-coating, as well as the effects of different surface treatments (UV ozone, oxygen plasma, functionalization). [1] A. P\'{e}nicaud, et al., \textit{J. Am. Chem. Soc. }\textbf{127}, 8 (2005). [2] C. Vall\'{e}s, et al., \textit{J. Am. Chem. Soc.} \textbf{130}, 15802 (2008). [Preview Abstract] |
Thursday, March 19, 2009 12:03PM - 12:15PM |
W26.00005: Anomalously high conductivity in bromine-intercalated graphite A.F. Hebard, S. Tongay, J. Hwang, D.B. Tanner, D. Maslov We have found that when graphite is intercalated with bromine, the \textit{ab}-plane ($c$-axis) conductivity sharply increases (decreases). Characterization of the Br intercalated samples by exposure time, weight uptake, sputter Auger spectroscopy and X-ray diffraction show a Br concentration that is uniformly distributed within a graphite host having an expanded interplanar spacing $d_{c}$. The \textit{ab}-plane conductivity is enhanced by several orders of magnitude in the temperature range from 300~K down to 1.7~K and shows no sign of saturation with increasing Br concentration. Hall measurements confirm a pronounced increase in the density of negative carriers consistent with an increased optical reflectivity (below 3000~cm$^{-1})$. The inferred plasma frequencies and extrapolated dc conductivities are consistent with the transport measurements. The diamagnetic susceptibility decreases with increasing Br concentration and follows a temperature dependence from which a Fermi energy that increases with increasing Br concentration is extracted. By increasing $d_{c}$, the \textit{ab}-plane conductivity of Br intercalated graphite begins to resemble the additive contributions of parallel connected doped graphene sheets and thus has implications for carbon based electronics. [Preview Abstract] |
Thursday, March 19, 2009 12:15PM - 12:27PM |
W26.00006: Influence of substrates on graphene layers: Raman study Jorge Camacho, Liyuan Zhang, Tony Valla, Igor Zaliznyak Electrical contacts and a substrate can significantly influence electronic and physical properties of graphene. Charge transfer, strain, introduction of various impurities and defects are some of the factors that can alter graphene properties. Therefore, the interaction with substrate and contacts has to be considered in any real graphene-based device. Here we use Raman spectroscopy to study effects of different substrates and adsorbates on graphene Raman-active modes. We find that the intensity, frequency and line-width of some modes are very sensitive to the chemical environment of graphene sheets, reflecting the changes in interactions of these modes with charge carriers and degree of disorder introduced in the system. [Preview Abstract] |
Thursday, March 19, 2009 12:27PM - 12:39PM |
W26.00007: Doping effect of electrode on Graphene Keyu Pi, Kathy McCreary, Wei Han , Yan Li, WenZhong Bao, Chun Ning Lau, Roland Kawakami Graphene as a carrier tunable transport media has drawn a lot of interest since its discovery. It has recently been reported that invasive electrode contacts cause electron-hole asymmetry [1] which will affect the transport properties. To study this effect, we developed an in-situ measurement system that combines Molecular Beam Epitaxy (MBE) with transport measurement. Fine control of the material deposition rate allows us to study the doping effect on graphene at the early stages of electrode formation. [1] B. Huard et al., PRB. \textbf{78}. 121402(R), 2008 [Preview Abstract] |
Thursday, March 19, 2009 12:39PM - 12:51PM |
W26.00008: Multi-layer graphene derived from graphite fluoride S.H. Cheng, K. Zou, A. Gupta, H.R. Gutierrez, P. Eklund, J.O. Sofo, J. Zhu, F. Okino We produce multi-layer graphene through the reduction of graphene fluoride. Graphite fluoride (CF) is synthesized by reacting F$_2$ with graphite at 500 - 600$^{o}$C. We obtain few- layer CF sheets through mechanical exfoliation and characterize their properties with electron diffraction, TEM, AFM, Raman and transport measurements. Electron diffraction spectra of fluorinated few-layer CF show the persistence of six-fold hexagonal symmetry and long-range in-plane crystalline order. Domains of varying thickness in both AFM and TEM measurements suggest an incomplete fluorination. Raman spectra of few-layer CF show the appearance of a D band ($\sim$1350 cm$^{-1}$) as expected from sp$^{3}$ bonding. Few-layer CF sheets are defluorinated in flowing H$_2$/Ar (10$\%$/90$\%$) at 500 - 600$^ {o} $C. AFM studies of defluorinated CF show a pronounced decrease in roughness and thickness, suggesting the removal of fluorine. Raman spectra of defluorinated CF show a reduced background with an enhanced 2D peak ($\sim$2700 cm$^{-1}$). We present transport measurements in field effect transistors fabricated from CF and defluorinated sheets and compare with that of pristine graphene and graphene-oxide reduced graphene. [Preview Abstract] |
Thursday, March 19, 2009 12:51PM - 1:03PM |
W26.00009: Size Selection of Metal Nanoparticles on Few Layer Graphene Luke A. Somers, Zhengtang Luo, E.J. Mele, A.T. Charlie Johnson We find layer number dependence in the size of metal nanoparticles grown on 1 to 10 layer graphene. Graphene is an attractive substrate for investigating and using nanoparticles due to its loose interaction with them. To preserve this condition it is ideal to grow particles in place rather than deposit them from solution. We find that annealing of evaporated metal nanoparticles on graphene and few layer graphene surfaces tightens their size distribution. The number of graphene layers changes the selected size. These results are in quantitative agreement with a model incorporating surface, bulk, and coulomb free energies. [Preview Abstract] |
Thursday, March 19, 2009 1:03PM - 1:15PM |
W26.00010: Growth of atomically smooth MgO films on graphene by molecular beam epitaxy. Kathleen McCreary, Wei Han, Wei-Hua Wang, Keyu Pi, Wenzhong Bao, Feng Miao, Roland Kawakami, Chun-Ning Lau Graphene has been the focus of many recent studies involving both electronic and spintronic devices due to its tunable charge carriers, high mobility, and possibility of long spin coherence lifetimes. To improve the spin injection into graphene spintonic devices, dielectric layers, such as MgO, are often used to minimize the conductivity mismatch between graphene and electronic contacts. We investigate the growth of MgO films on graphene by molecular beam epitaxy and find that surface diffusion promotes a rough morphology. To reduce the mobility of surface atoms, the graphene surface is dressed by Ti atoms prior to MgO deposition. With as little as 0.5 ML monolayer of Ti, the MgO overlayer becomes atomically smooth. Single layer graphene has been patterned into nanoscale devices to study the effect of the Ti dressing layer and MgO overlayer on the electronic and spintronic properties. [Preview Abstract] |
Thursday, March 19, 2009 1:15PM - 1:27PM |
W26.00011: Optimization of high quality epitaxial graphene growth on SiC Ming Ruan, Michael Sprinkle, Yike Hu, Claire Berger, Walter de Heer We have developed an RF inductance furnace to grow epitaxial graphene(EG) of very high quality on SiC. EG has attracted much attention during the past years due to its potential as next generation of material for electronic devices. The formation of graphene on silicon carbide by sublimation of Si is a complicated process that is not well understood yet. We present here our latest result on the growth of epitaxial graphene in low vacuum. The research is carried out for multilayer graphene growth on 4H SiC (000$\overline{1}$) and (0001) face. Atomic force microscopy(AFM), ellipsometry, Raman spectroscopy and resistivity measurement are adopted as characterization tools. The stepped terrace structure on the SiC surface changes with the graphene layer growth conditions. Terraces larger than 20$\mu$m with flat graphene layers extended over the steps are achieved. We demonstrated a path towards mass production of high quality EG chips. [Preview Abstract] |
Thursday, March 19, 2009 1:27PM - 1:39PM |
W26.00012: Growing Epitaxial Graphene on an Insulator by MBE Chandra Mohapatra, James Eckstein We have used electron beam evaporation of solid carbon (C) to deposit graphene on MgO $<$111$>$ at 850C. The growth appears epitaxial as observed by in-situ RHEED which also reveals that the hot scattering surface transitions from an insulator to a conductor after deposition of 1 monolayer of C. Growth at higher temperatures gives better crystallinity. We further characterize the film by ex-situ Raman spectroscopy, AFM and transport. Raman reveals all the characteristic G, D and 2D peaks of graphene and the 2D peak can be fit to a single lorentzian typical for graphene. AFM pictures show that the surface consists of flat connected domains, which are uniform across the substrate. Electrical transport shows insulating behavior with resistance (R) varying as $1/T^2$. This work was supported by the DOE BES at the F. Seitz Materials Research Laboratory at the University of Illinois, Urbana. [Preview Abstract] |
Thursday, March 19, 2009 1:39PM - 1:51PM |
W26.00013: The effect of self-assembled monolayers on graphene conductivity and morphology T. L. Moore, J. H. Chen, B. Riddick, E. D. Williams Graphene transport properties are limited by charge defects in SiO$_{2}$, and by large charge density due to strong interaction with SiC. To modify these effects we have treated 300 nm SiO$_{2}$ with tricholosilanes with different termination groups including pure and fluoro and amino-terminated hydrocarbons for use as substrates for mechanical exfoliation of graphene. XPS measurements verify the presence of the expected termination groups. AFM measurements reveal modified monolayer roughness and correlation lengths; for a fluorinated carbon chain the RMS roughness is 0.266 $\pm $ 0.017 nm and the correlation length is 10.2 $\pm $ 0.7 nm compared to 0.187 $\pm $ 0.011 nm and 19.8 $\pm $ 2.5 nm for SiO$_{2}$. Surface free energies of the monolayers and the SiO$_{2}$ blank have been computed from static contact angle measurements and all decrease the SiO$_{2 }$surface free energy; for the fluorinated carbon chain monolayer a decrease of 20 mJ/m$^{2}$ from SiO$_{2}$. We will discuss the ease of exfoliation, and the morphology and conductivity of graphene on these monolayers. [Preview Abstract] |
Thursday, March 19, 2009 1:51PM - 2:03PM |
W26.00014: The effect of SiO$_{2}$ surface states on the electronic characteristics of graphene FET devices Jorge Sofo, Ning Shen, Hugo Romero, Peter Eklund Electronic states localized at the surface of oxide semiconductors are a common cause of their low ionization potential. We study the properties of the SiO$_{2}$ surface states using density functional theory (DFT) and show that they strongly affect the intrinsic doping of graphene on oxidized silicon substrates. We present simple empirical model that it is parameterized from the DFT calculations. The model demonstrates that Dirac voltages as large as 50~V and intrinsic n-doping are produced by the presence of these surface states. We extend it to include the effect of other adsorbates, such as water, that modify the dielectric properties of the device. [Preview Abstract] |
Thursday, March 19, 2009 2:03PM - 2:15PM |
W26.00015: Efficient manipulation of zigzag and armchair edges in graphene nanoribbons by joule heating Xiaoting Jia, Mario Hofmann, Vincent Meunier, Bobby Sumpter, Jessica Campos-Delgado, Jose Romo-Herrera, Hyungbin Son, Ya-Ping Hsieh, Alfonso Reina, Jing Kong, Mauricio Terrones, Mildred Dresselhaus Edge study in graphene nanoribbons has attracted lots of interest in recent years, due to the different electronic properties of the ribbons arising from zigzag and armchair edges. Here we demonstrate and monitor an efficient crystallization process for graphite nanoribbon edges by Joule heating inside an integrated transmission electron microscope (TEM) equipped with a scanning tunneling stage STM (TEM-STM system). With this system we were able to produce for the first time atomically smooth zigzag or armchair edges from defective rough edges present in graphite nanoribbons, by applying a controlled voltage, while observing the structural behavior in-situ. Edge motion along certain preferred crystallographic orientations is observed, and the transformational effects of Joule heating and applied electric field are described. This work demonstrates both the possibility of self-eliminating lattice defects by applying a bias voltage, and an effective way to produce clean zigzag and armchair edges, which could be useful for both fundamental studies of edge reactivity, magnetism and the development of future electronics applications. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2025 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700