Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session H30: Graphene: Synthesis and Characterization |
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Sponsoring Units: DCMP Chair: Paul Campbell, Naval Research Laboratory Room: C147/154 |
Tuesday, March 22, 2011 8:00AM - 8:12AM |
H30.00001: Electrical breakdown of graphene and few-layer graphene structures Abhishek Sundararajan, Stephen Johnson, D. Patrick Hunley, Roel Flores, A.T Charlie Johnson, Douglas Strachan The electrical breakdown of graphene and few-layer graphene (FLG) structures are investigated. To better understand the dynamics of these nano-scale thermal effects, we investigate graphene and FLG nanowires of various dimensions and find that significant joule heating occurs inducing the structures to evolve. A distinct change in the behavior during electrical stressing indicates that different mechanisms occur at the various stages of evolution. The results are compared to detailed thermal modeling of our structures and could have implications on the development of high current carrying nanoscale graphene devices. Supported in part by NSF Award No. DMR-0805136, the Kentucky NSF EPSCoR program, the University of Kentucky Center for Advanced Materials, and the University of Kentucky Center for Nanoscale Science and Engineering. [Preview Abstract] |
Tuesday, March 22, 2011 8:12AM - 8:24AM |
H30.00002: Designing all-graphene nano-junctions by covalent functionalization Caterina Cocchi, Alice Ruini, Deborah Prezzi, Marilia J. Caldas, Elisa Molinari We study the effect of covalent edge functionalization, with organic functional groups, on the opto-electronic properties of graphene nano-flakes and nano-junctions. We work within the frame of Hartree-Fock-based semi-empirical methods [1,2]. Our study shows that functionalization can be designed to tune electron affinities and ionization potentials of graphene flakes. The stability of the proposed mechanism is analyzed with respect to the functional groups, the functionalization rate and the width of graphene nanostructures. We show that this effect can be exploited to realize type-II all-graphene nano-junctions. Different frontier orbital alignments can be engineered varying the functionalization, leading to specific optical properties: The conditions to obtain charge transfer excitations are investigated.\\[4pt] [1] Dewar, et al., J. Am. Chem. Soc. 107, 3902 (1985)\\[0pt] [2] Ridley and Zerner, Theoret. Chim. Acta 32, 111 (1973) [Preview Abstract] |
Tuesday, March 22, 2011 8:24AM - 8:36AM |
H30.00003: Schottky diode via dielectrophoretic assembly of reduced graphene oxide sheets between dissimilar metal contacts Muhammad R. Islam, Daeha Joung, Saiful Khondaker Reduced graphene oxide (RGO) has attracted significant attention due to its ability to produced graphene nanostructures in large quantities. It has been also considered as a promising building block for future generation of electronic and optoelectronic devices. Here we demonstrate fabrication of RGO Schottky diodes with high yield via dielectrophoretic (DEP) assembly between two dissimilar metal contacts. Titanium (Ti) was used to make a Schottky contact, while palladium (Pd) was used to make an Ohmic contact. From the current - voltage characteristics, we obtain rectifying behavior with a rectification ratio of up to 600. The ideality factor was high (4.9) due to the presence of a large number of defects. The forward biased threshold voltage was 1 V while the reverse bias breakdown voltage was - 3.1 V which improved further upon mild annealing at 200\r{ } C and can be attributed to an increase of work function of RGO due to annealing. [Preview Abstract] |
Tuesday, March 22, 2011 8:36AM - 8:48AM |
H30.00004: Graphitic carbon molecular beam epitaxy on dielectric substrates Ulrich Wurstbauer, Rui He, Albert Rigosi, Theanne Schiros, Annette Plaut, Loren N. Pfeiffer, Philip Kim, Abhay Pasupathy, Aron Pinczuk, Jorge M. Garcia We report on growth of thin large area graphitic layers on dielectric substrate materials by means of molecular beam epitaxy (MBE) under UHV conditions. This solid source MBE technique offers highly controllable conditions without the need of gas precursors or metal surfaces. Our initial experiments on dielectric substrates such as mica, SiO$_2$ and BN clearly demonstrates the potential of this new growth technique. NEXAFS studies show that the binding mechanism in our sheets is dominated by sp$^2$ bonds and the Raman spectra confirm their graphitic nature. We will also describe STM measurements of the topography and local electronic structure of these films. [Preview Abstract] |
Tuesday, March 22, 2011 8:48AM - 9:00AM |
H30.00005: Stability of epitaxial graphene on pristine Si(111) Branden Kappes, Teresa Davies, Sukky Jun, Adri van Duin, Cristian Ciobanu Incorporation of carbon nanostructures with silicon-based nanoelectronics will involve the direct integration of graphene with silicon chips, but so far graphene has not been grown on pristine silicon surfaces. Because usual synthesis routes would likely lead to the formation of silicon carbide, we calculate the binding energy of graphene transferred onto the Si(111) surface and also analyze its stability at various temperatures. Our calculations based on (commensurate) moir\'e superstructures with periodic boundary conditions show a strong graphene--substrate binding, about 1.5 eV/carbon atom, over a wide range of in-plane orientations of the graphene layer. Molecular dynamics simulations based on bond-order and reactive force field interatomic potentials suggest that the graphene binds to the substrate where carbon is rehybridized sp$^{3}$, and that this rehybridized graphene structure does not lead to the decomposition of graphene into silicon carbide even at temperatures as high as 80\% of the substrate melting temperature. [Preview Abstract] |
Tuesday, March 22, 2011 9:00AM - 9:12AM |
H30.00006: Synthesis and characterization of graphene patterned with Fe$_{3}$O$_{4}$ nanoparticles Sayan Chandra, K. Stojak, D. Ferizovic, M. Munoz, M.H. Phan, H. Srikanth Graphene has emerged as a very exciting material with its outstanding physical, chemical, and mechanical properties. Due to the presence of excess free electrons on a graphene surface, the possibility of graphene-mediated long-range interactions between magnetic nanoparticles would open up new avenues of research and device development. Our studies aimed to deposit $\sim $9 nm Fe$_{3}$O$_{4}$ NPs on graphene layers to understand the role of the metallic interface in mediating the magnetic interactions between the particles. We successfully grew the high-quality graphene on Ni films using CVD and used the Langmuir-Blodgett technique to pattern different layers of the Fe$_{3}$O$_{4}$ nanoparticles on the graphene sheets. The samples were well structurally characterized by XRD, TEM, AFM, and Raman spectroscopy. Interestingly we have observed strong variation in the magnetic properties such as magnetic anisotropy of the NPs pattered graphene samples when compared to just the NPs. These results point to the important role of the metallic interface in mediating the magnetic interactions between the Fe$_{3}$O$_{4}$ nanoparticles. [Preview Abstract] |
Tuesday, March 22, 2011 9:12AM - 9:24AM |
H30.00007: Scaled-Up Synthesis and Characterization of High-Purity Graphene Patricia Johnson, Mark Griep, Kristopher Behler, Rose Pesce-Rodrequez, Shashi Karna, Wendy Sarney, Kate Duncan Graphene, a two-dimensional, single-atom sheet of carbon atoms, discovered in 2004, has emerged as a new class of novel nano-scale material due to its unique chemical and physical properties, and potential applications in a wide range of civilian and military technologies. However, a major challenge in its technological application is a lack of chemical/physical method(s) to produce/synthesize high-purity graphene in viable quantity. Another challenge in the technological application of graphene is a lack of detailed understanding of its structure-property relationship. In order to address these issues, we have developed a chemical exfoliation method that yields high-purity graphene in bulk quantity. The method is scalable to produce large quantities of high purity graphene. In this paper, we present the results of our synthetic approach and structure-property characterization of graphene. [Preview Abstract] |
Tuesday, March 22, 2011 9:24AM - 9:36AM |
H30.00008: Two-Dimensional Molecular Crystals of Phosphonic Acids on Graphene Mariana Prado, Bernardo Neves, Regiane Nascimento, Luciano Moura, Matheus Matos, Mario Mazzoni, Luiz Cancado, Helio Chacham The synthesis and characterization of two-dimensional (2D) molecular crystals comprised of long and linear phosphonic acids atop graphene is reported. Using scanning probe microscopy in combination with first-principles calculations, we show that these true 2D crystals are oriented along graphene armchair direction only, thereby enabling an easy determination of graphene flake orientation. We have also compared the doping level of graphene flakes via Raman spectroscopy. The presence of the molecular crystal atop graphene induces a well-defined shift in the Fermi level, corresponding to hole doping, which is in agreement with our ab initio calculations. [Preview Abstract] |
Tuesday, March 22, 2011 9:36AM - 9:48AM |
H30.00009: Carbon chains grown perpendicularly on graphene: Nanobrush Can Ataca, Salim Ciraci We predict a peculiar growth process, where carbon adatoms adsorbed to graphene readily diffuse above room temperature and form linear chains. These chains grow longer on graphene through insertion of carbon atoms one at a time from the bottom end. Through this growth process two allotropic forms of carbon, namely graphene and polyyne are combined to make several novel nanostructures. Brush like graphene sheets with protruding polyynes can achieve chemical activity and attain new functionalities. [Preview Abstract] |
Tuesday, March 22, 2011 9:48AM - 10:00AM |
H30.00010: Size Control of Nanographene Directly Grown On Glass Jaewu Choi We directly deposited very thin carbon film was on glass by thermal chemical deposition at 750 $^{\circ}$C without using any catalyst. The directly deposited carbon film consists of nanographene with an in-plane crystal size of $\sim $ 15 nm. The in-plane crystal size of nanographene increased up to 23 nm by annealing of the post-deposited nickel film on the nanographene film at 300 $^{\circ}$C to 500 $^{\circ}$C. This study suggests that nanographene can be directly deposited on glass at low temperature and that the crystalline size can be controlled. [Preview Abstract] |
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