Bulletin of the American Physical Society
79th Annual Meeting of the APS Southeastern Section
Volume 57, Number 16
Wednesday–Saturday, November 14–17, 2012; Tallahassee, Florida
Session EA: Nanoscale Physics |
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Chair: Mark Jack, Florida A&M University Room: DoubleTree Ballroom |
Thursday, November 15, 2012 3:45PM - 4:15PM |
EA.00001: Synthesis, structure and electrical properties of carbon nanotube junctions Invited Speaker: Wenzhi Li Carbon nanotubes have great promise for applications in electronics, optics, materials science, energy storage, and sensor technology due to their interesting electronic and mechanical properties which are determined by their unique morphologies and structures. In this presentation, the growth mechanism, structure, and electrical property of multi-walled carbon nanotube junctions as well as the mechanical property of single-walled carbon nanotubes will be discussed. Specifically, this talk will discuss (1) the influence of the carbon precursor (thiophene) vapor concentration on the formation of the carbon nanotube junctions during the chemical vapor deposition process, (2) the correlation between the electrical property and the structure of the carbon nanotube junctions, and (3) the radial elasticity of individual single-walled carbon nanotubes measured by using atomic force microscopy (AFM). [Preview Abstract] |
Thursday, November 15, 2012 4:15PM - 4:45PM |
EA.00002: Van der Waals Interactions in Graphene Nanoribbons -- Important Implications revealed via Theoretical Investigations Invited Speaker: Lilia Woods Graphene nanoribbons (GNRs) are quasi-one dimenisional structures with planar geometry. They have extraordinary properties suitable for novel technological applications, especially for high speed electronics. Of particular importance is how GNRs interact with each other and other materials not only to understand their fundamental science, but also to help interpret experimental data and design better devices. Because of their inertness and nature of CC bonding, van der Waals (vdW) forces at small separations dominate GNR interactions. I will present studies revealing the collective microscopic nature of GNR vdW interactions based on a discrete dipole approximation. Calculations utilizing Density Functional Theory (DFT) with semi-empirical correction for the vdW interactions will also be presented for folded GNRs. In all cases, the emphasis will be on understanding the peculiarities of the vdW force in terms of registry dependence, strength, and role in mechanical manipulations involving GNRs. Furthermore, I will emphasize electronic structure modulations in terms of overall changes, energy gaps, magnetic states in various folded configurations as obtained via DFT. [Preview Abstract] |
Thursday, November 15, 2012 4:45PM - 5:15PM |
EA.00003: Electronic Transport Investigations of Reduced Graphene Oxide Sheet Invited Speaker: Daeha Joung Reduced graphene oxide (RGO) sheet, a chemically functionalized atomically thin carbon sheet, provides a convenient pathway for producing large quantities of graphene via solution processing. The easy processibility of RGO sheet and its composites offer interesting electronic, chemical and mechanical properties that are currently being explored for advanced electronics and energy based materials. However, a clear understanding of electron transport properties of RGO sheet is lacking which is of great significance for determining its potential application. In this talk, we will present fabrication of high-yield solution based graphene field effects transistor (FET) using AC dielectrophoreis (DEP) and investigate the detailed electronic transport properties of the fabricated devices. The majority of the devices show ambipolar FET properties at room temperature. However, the mobility values are found to be lower than pristine graphene due to a large amount of residual defects in RGO sheets. We calculated the density of these defects by analyzing the low temperature (300 to 77K) charge transport data using space charge limited conduction (SCLC) with exponential trap distribution. At very low temperature (down to 4.2 K), we observe Coulomb blockade (CB) and Efros-Shklovskii variable range hopping (ES-VRH) conduction in RGO implying that RGO can be considered as a graphene quantum dots array (GQD), where graphene domains act like QDs while oxidized domains behave like tunnel barriers between QDs. This was further confirmed by studying RGO sheets of varying carbon sp$^2$ fraction from 55\%-80\% and found that both the localization length and CB can be tuned. From the localization length and using two band Kane model, we estimate tunable band gap of RGO sheets with varying carbon sp$^2$ fraction. [Preview Abstract] |
Thursday, November 15, 2012 5:15PM - 5:45PM |
EA.00004: Electron interaction effects in graphene Invited Speaker: Daniel Sheehy Graphene, a one-atom thick sheet of graphite, has received a large amount of attention following its recent experimental isolation. At low energies, graphene possesses an emergent relativistic symmetry, and can be described in terms of linearly-dispersing massless ``Dirac'' fermions, with a velocity that is determined by band structure and experimentally measured to be 300 times smaller than the speed of light. This approximate relativistic behavior is, however, broken by the presence of the long-ranged Coulomb interaction, although many experiments can be explained in terms of a non-interacting picture. I will discuss how the Coulomb interaction will be manifested in various experimentally observable quantities, including the heat capacity, diamagnetic response, and optical conductivity. I will also discuss the implications of recent experiments on the optical transparency of graphene. [Preview Abstract] |
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