Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session V31: Nanotubes: Transport |
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Sponsoring Units: DCMP Chair: Laxmidhar Senapati, Naval Research Laboratory Room: Baltimore Convention Center 328 |
Thursday, March 16, 2006 11:15AM - 11:27AM |
V31.00001: Ab initio charge transport through N-doped carbon nanotubes: microscopic understanding of carbon nanotube sensors Frederico D. Novaes, Mariana Rossi, Ant\^{o}nio J. R. da Silva, A. Fazzio We calculate, using an ab initio non-equilibrium Green's function formalism, the conductance of metallic carbon nanotubes with pyridine-like defects. We show that there is a decrease of the conductance at the Fermi energy due to these defects, which is caused by nitrogen related levels within an energy window of 1.5 eV below the Fermi energy. We then investigate how exposure to NH3 can affect the conductance. At the pyridine- like structure the NH3 dissociated into NH2 and H, with both molecules binding to nitrogen atoms. This configuration leads to an increase of the conductance, and cannot, therefore, explain the increase of resistance that has been experimentally observed. We then investigate other configurations, and suggest that a possible cause of the resistance increase is adsorption of atomic or molecular species at the wall of pristine nanotubes. [Preview Abstract] |
Thursday, March 16, 2006 11:27AM - 11:39AM |
V31.00002: A Semi-Empirical Approach to Bandstructure, Chemistry and Transport: Extended H\"uckel Theory applied to Carbon Nantotubes and Silicon - Diego Kienle, Jorge Cerda, Kirk Bevan, Gengchiau Liang, Lutfe Siddiqui, Avik Ghosh, M.P. Anantram We apply semi-empirical Extended H\"uckel Theory (EHT) to calculate electronic structure and zero bias density-of states and transmission for two technologially important materials: carbon nantotubes and silicon. We demonstrate that the EHT-parameters optimized for bulk-silicon and 2D-graphene are transferable to describe qualitatively and quantitatively the electronic structure of structural deformed systems such as small diameter CNTs and relaxed silicon surfaces for different orientations. Finally, we show that the non-orthogonal EHT-approach can handle electronic structure and bonding chemistry simultaneously considering a carbon-monoxide-CNT heterostructure as example for a molecule sensor.To study transport through large nanoscale devices along with attached molecules a semi-empirical approach such as EHT might offer a good compromise between computational expensive DFT-methods and effective mass models which do not capture molecular features. [Preview Abstract] |
Thursday, March 16, 2006 11:39AM - 11:51AM |
V31.00003: Ab initio Bandbending and Schottky Barriers of a Carbon Nanotube and Boron Nitride Device Khorgolkhuu Odbadrakh, Pawel Pomorski, Christopher Roland The quantum transport characteristics of two semiconducting nanotubes (i.e., single-wall (8,0) carbon and boron nitride nanotubes) coupled to metallic leads (i.e., Al (100)) was investigated with a combined nonequilibrium Greens function/density functional theory formalism. The resulting transmission depends very muchon the size of the nanotubes: very short tubes are characterized by metallic current-voltage behavior because of transmission via evanescent modes, while longer tubes are dominated by bandbending and Schottky barrier phenomena. An analysis of the latter phenomena as a function of nanotube characteristics, charge transfer, and gate voltage will be presented. [Preview Abstract] |
Thursday, March 16, 2006 11:51AM - 12:03PM |
V31.00004: Effect of Strain and Defects on Transport Properties of Carbon Nanotubes Yao He, Chun Zhang, Chao Cao, Hai-Ping Cheng Strain dependence of electronic transport properties of carbon nanotubes has been studied using first-principles calculations. We have found that the quantum conductance decreases monotonically with increasing strain, due to the strain-dependent contribution of molecular orbitals. Transport properties are also affected by the presence of defects. Our results have demonstrated that the electronic transport properties of a nano-scale device are closely related to the nature of the band structure of the metallic lead and the details of chemical bonding in the scattering region. Acknowledgement: DOE/BES under grant FG02-02ER45995 [Preview Abstract] |
Thursday, March 16, 2006 12:03PM - 12:15PM |
V31.00005: Dependence of transport through carbon nanotubes on local Coulomb potential. Alexey Zhukov, Alexander Makarovski, Matthew Prior, Gleb Finkelstein With home made atomic force microscope we perform scanned probed imaging of single-walled carbon nanotube devices at 4.2 K. We also observe changing of the heights and positions of the conductivity peaks in Coulomb Blockade regime with displacement of the AFM conductive tip. Influence of the Coulomb potential of the AFM tip on single-electron charge states in carbon nanotube is discussed. [Preview Abstract] |
Thursday, March 16, 2006 12:15PM - 12:27PM |
V31.00006: Origin of hysteresis in gate-modulated transport in single-wall carbon nanotubes Swastik Kar, Aravind Vijayaraghavan, Saikat Talapatra, Caterina Soldano, Saroj K. Nayak, Omkaram Nalamasu, Pulickel M. Ajayan Transfer characteristics of gate-modulated transport in single-wall carbon nanotubes show significant hysteresis. This hysteresis is usually attributed to a screening of the gate voltage due to mobile charges/ions in the presence of a trapping/de-trapping mechanism within the gate architecture. From a temperature dependence of the hysteresis behavior, we suggest an alternate mechanism, where the screening charges are injected from the nanotube itself into the surrounding dielectric. Any trapping/de-trapping mechanism does not appear to play a significant role, and the experimental results can be understood in terms of a capacitive charging of the surrounding dielectric. [Preview Abstract] |
Thursday, March 16, 2006 12:27PM - 12:39PM |
V31.00007: Electrical transport properties of selective area CVD grown single wall carbon nanotube devices Zhixian Zhou, Rongying Jin, Gyula Eres, David Mandrus Individual single wall carbon nanotube (SWNT) devices were constructed by the direct assembly of an individual SWNT on two opposing Au electrons using an acetylene based low temperature selective area Chemical Vapor Deposition (CVD) method. Standard electron beam lithography and subsequent electron-gun assisted metal deposition were used to fabricate both the electrodes and catalyst islands. Electrical transport properties of the SWNT circuits were measured by applying a gate voltage to the Si substrate at various temperatures down to 0.3 K. Both semiconducting and metallic individual SWNTs were found bridging the Au electrodes with relatively small contact resistances. The semiconducting SWNTs exhibit a significant electrical field effect at room temperature with the conductance modulation approaching 5 orders of magnitude. High bias measurements on both suspended and substrate-supported metallic SWNTs reveal strikingly different phenomena. The details of the electrical transport results will be discussed. [Preview Abstract] |
Thursday, March 16, 2006 12:39PM - 12:51PM |
V31.00008: Electron transport in as-grown suspended semiconducting carbon nanotubes Vikram Deshpande, Marc Bockrath Recently it was reported [1] that as-grown suspended single-walled carbon nanotubes (SWNTs) contacted with Pt or Mo leads afford devices that are devoid of perturbations due to substrate interaction and relatively defect-free. Previously, low-resistance contacts to semiconducting SWNTs have been obtained with Au [2], since the work-function of Au aligns with the valence band of the SWNTs creating ohmic contacts in the p-type region. We present fabrication of as-grown SWNTs with Au contacts, to fully exploit this behavior. We discuss electron transport in semiconducting devices obtained as above, with the aim of understanding the role of electron interactions in transport. Metallic SWNTs are known to exhibit Luttinger liquid behavior as is evident in the power-law dependence of conductance and density of states in a tunneling experiment [3]. We explore Luttinger liquid behavior in devices obtained using our fabrication technique. We will present latest experiments and inferences. [1] Cao et al, Nature Materials (2005) [2] Yaish et al, PRL (2004) [3] Bockrath et al, Nature (1999) [Preview Abstract] |
Thursday, March 16, 2006 12:51PM - 1:03PM |
V31.00009: The effect of purification on electron transport properties of single-wall carbon nanotubes Hisashi Kajiura, Masashi Shiraishi, Masafumi Ata, Anil Nandyala, Ulas Coskun, Alexey Bezryadin The effect of purification on room temperature electronic transport properties of laser-produced single-wall carbon nanotubes (SWNTs) was studied by submerging the nanotubes into liquid mercury. As-produced SWNTs were purified using H2O2, HCl, and NaOH solutions and heated at 923K at 0.01Pa for 1 h. Purified SWNTs having clean surface wall showed weak dependence of the electrical resistance on the length of the nanotube segment connecting electrodes. This provides evidence of quasi-ballistic electron transport in SWNTs. The estimated electronic mean free path of the purified SWNTs reached a few microns, which is longer than that of as-produced tubes. The electronic mean free path in purified SWNTs is consistent with the calculation based on the electron scattering by acoustic phonons. [H. Kajiura et al. Appl Phys Lett 86, 2005, 122106.] [Preview Abstract] |
Thursday, March 16, 2006 1:03PM - 1:15PM |
V31.00010: Probing the transport property of each individual wall within a multiwall carbon nanotube X. Yan, J.Y. Huang, S. Chen, Z. Wang, G. Chen, M.S. Dresselhaus, Z.F. Ren We report the atomic-scale imaging with concurrent transport measurements of the breakdown$^{ }$of individual multiwall carbon nanotubes inside a transmission electron microscope equipped with a piezo manipulator [1]. We found unexpectedly three distinct breakdown sequences, namely, from the outermost wall inward, from the innermost wall outward, and alternatively between the innermost and the outmost walls. Remarkably, a significant amount of current drop was observed when an innermost wall is broken, proving unambiguously that every wall is conducting. Moreover, the breakdown of each wall in any sequence initiates in the middle of the nanotube, not at the contact, proving that the transport is not ballistic. [1] J. Y. Huang et al., Phys. Rev. Lett. 94, 236802 (2005). [Preview Abstract] |
Thursday, March 16, 2006 1:15PM - 1:27PM |
V31.00011: Electronic transport in single-walled nanotubes of known chiral indices R. Caldwell, F. Wang, Y. Wu, M. Huang, L. Huang, S. O'Brien, T.F. Heinz, J. Hone By measuring the Rayleigh scattering spectra of individual single-walled carbon nanotubes, we are able to measure the optical transition energies and therefore deduce the chiral indices (n,m).~ Using a simple mechanical transfer process, we can transfer the optically characterized tubes to a substrate.~ Following fabrication of metallic leads using e-beam lithography, the electrical transport properties of these tubes can be probed.~ We will present data on semiconducting, chiral metal and armchair metal SWNTs. [Preview Abstract] |
Thursday, March 16, 2006 1:27PM - 1:39PM |
V31.00012: Hopping Conduction in Individual Template-Produced Multiwalled Carbon Nanotubes D. P. Wang, B. R. Perkins, A. J. Yin, D. E. Feldman, A. Zaslvasky, J. M. Xu We report electrical transport measurements of individual multiwalled carbon nanotubes grown catalytically in a nonporous anodic aluminum oxide template by thermal chemical vapor deposition of acetylene. The conductance shows an exp[-($T_{0}$/$ T)^{1/2}$] dependence on temperature $T$ and exp[-$\xi _{0}$/$\xi $] dependence on the applied electric field $\xi $ in the high field regime, suggesting that hopping conduction between the grains is the dominant transportation mechanism. As the nanotubes are granular and highly defective, annealing has been used to change the granularity. Similar $T$- and $\xi $- dependence of conductance is observed for annealed nanotubes with different granularity-related coefficients $T_{0 }$and $\xi _{0}$. Small magnetoresistance is observed for both types of nanotubes. Comparison with theory is presented and the $T_{0 }$and $\xi _{0}$ coefficients are used to extract the characteristic conducting grain size. [Preview Abstract] |
Thursday, March 16, 2006 1:39PM - 1:51PM |
V31.00013: Thermal effects in non-linear electronic transport in metallic carbon nanotubes Marcelo Kuroda, Jean-Pierre Leburton Recent experiments have shown that metallic carbon nanotubes exhibit different $IV$ characteristics depending on whether or not they lie on a substrate. These interesting features range from current saturation to negative differential resistance at high bias. In this talk, we present a model based on the solution of the Boltzmann transport equation that accounts for the interplay between thermal and electronic transport in the metallic system. Our results reproduce the experimental observations and emphasize the role of heat dissipation in the nanotube non-linear characteristics. [Preview Abstract] |
Thursday, March 16, 2006 1:51PM - 2:03PM |
V31.00014: Thermal Transport in MWNT sheet. Ali Aliev, Mei Zhang, Shaoli Fang, Sergey Lee, Anvar Zakhidov, Ray Baughman We present the comparative study of the anisotropic thermal conductivity and the thermal diffusivity of aligned multiwalled carbon nanotube sheet using two methods: laser flash and 3 omega methods. The highly aligned transparent nanotube sheets are drawn from a sidewall of a multiwalled carbon nanotube (MWNT) forest that was synthesized by chemical vapor deposition. The sectional analysis by AFM tip shows that suspended sheet consists on average one layer of 10 nm MWNT. Increase of the sheet density by stacking the layer to layer decreases the thermal conductivity and thermal diffusivity due to phonon-phonon interaction. High thermal conductivity and thermal diffusivity of studied specimens combined with extremely high surface area suggests a variety of application of MWNT sheets. [Preview Abstract] |
Thursday, March 16, 2006 2:03PM - 2:15PM |
V31.00015: Nanotube-Metal Junctions: 2- and 3- Terminal Electrical Transport San-Huang Ke, Weitao Yang, Harold U. Baranger We address the quality of electrical contact between carbon nanotubes and metallic electrodes by performing first-principles calculations for the electron transmission through ideal 2- and 3-terminal junctions, thus revealing the physical limit of tube-metal conduction. The structural model constructed involves surrounding the tube by the metal atoms of the electrode as in most experiments; we consider metallic (5,5) and n-doped semiconducting (10,0) tubes surrounded by Au or Pd. In the case of metallic tubes, the contact conductance is shown to approach the ideal $4e^2/h$ in the limit of large contact area. For three-terminals, the division of flux among the different transmission channels depends strongly on the metal material. A Pd electrode has nearly perfect tube-electrode transmission and therefore turns off the straight transport along the tube. The carrier injection is found to occur only at the edge of the contact region. Our results are in good agreement with some recent experimental reports and clarify a fundamental discrepancy between theory and experiment. [Preview Abstract] |
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