Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session S30: Nanotubes, Transport, and Other Properties |
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Sponsoring Units: DCMP Chair: Vincent Crespi, Pennsylvania State University Room: Morial Convention Center 222 |
Wednesday, March 12, 2008 2:30PM - 2:42PM |
S30.00001: Direct observation of gate-controlled Josephson inductance in multiwalled carbon nanotube Antti Paila, Lorenz Lechner, Markus Gaass, Christoph Strunk, Mika Sillanp\"a\"a, Pertti Hakonen Electrometers based on Cooper pair tunneling are, in principle, dissipationless, and thus advantageous due to their small back action noise. We have studied the so called L-SET circuit, in which the frequency of Josephson plasma oscillations in a superconducting junction device is tuned below one GHz by a parallel $LC$ circuit. In the present work, we have used a Josephson junction made out of a multiwalled carbon nanotube with Pd/Nb contacts. We observe gate-tunable critical currents up to $I_c \sim 10$ nA, which are deduced from shifts in the LC-circuit resonance frequency caused by the Josephson inductance ($\propto I_c^{-1}$) of the MWNT junction. This work was financially supported by Academy of Finland and by European Union (CARDEQ, FP6-IST-021285-2). [Preview Abstract] |
Wednesday, March 12, 2008 2:42PM - 2:54PM |
S30.00002: ABSTRACT WITHDRAWN |
Wednesday, March 12, 2008 2:54PM - 3:06PM |
S30.00003: Electronic transport in inhomogeneous quantum wires Jerome Rech, K. A. Matveev We study the transport properties of a long non-uniform quantum wire where the electron-electron interactions and the density vary smoothly at large length scales. We show that these inhomogeneities lead to a finite resistivity of the wire, due to a weak violation of momentum conservation in the collisions between electrons. Estimating the rate of change of momentum associated with non-momentum-conserving scattering processes, we derive the expression for the resistivity of the wire in the regime of weakly interacting electrons and find a contribution linear in temperature for a broad range of temperatures below the Fermi energy. By estimating the energy dissipated throughout the wire by low-energy excitations, we then develop a different method for deriving the resistivity of the wire, which can be combined with the bosonization formalism. This allows us to compare our results with previous works relying on an extension of the Tomonaga-Luttinger model to inhomogeneous systems. [Preview Abstract] |
Wednesday, March 12, 2008 3:06PM - 3:18PM |
S30.00004: ABSTRACT WITHDRAWN |
Wednesday, March 12, 2008 3:18PM - 3:30PM |
S30.00005: Carbon Nanotubes in Helically Modulated Potentials Paul Michalski, Eugene Mele We study the low energy electronic spectrum of metallic and semi-conducting carbon nanotubes (CNTs) under an applied, helically symmetric potential using the long-wavelength, continuum approximation. We find that the effects of the external potential depend on the strength of the potential and on the dimensionless ratio of the nanotube circumference to the pitch of the helical potential, and we explore the system's response as these two parameters are varied. We find that for semi-conducting CNTs the band gap is always reduced. For metallic CNTs the Fermi velocity is reduced, and in very strong fields two small gaps appear at the Fermi surface in addition to the gapless Dirac point. We develop a simple model to estimate the magnitude of the potential strength and its effect on the spectrum of a DNA-CNT complex in aqueous solution. [Preview Abstract] |
Wednesday, March 12, 2008 3:30PM - 3:42PM |
S30.00006: Effective Low Energy Lattice Models for Conducting Carbon Nanotubes Sebastian A. Reyes, Alexander Struck, Sebastian Eggert We obtain effective one dimensional lattice theories for the low energy sector of conducting single walled carbon nanotubes. The effective Hamiltonians are otained by keeping only the conducting bands of the tube, but without taking the a continuum limit. For the zigzag and armchair tubes the theory is particularly simple and reduces to two species of well defined orbitals with only nearest neighbor hopping. These models provide a clear picture of the low energy physics of carbon nanotubes on a lattice without linearization. Correlation functions and density oscillations can be calculated. We show how arbitrary bare electron electron interactions can be included. [Preview Abstract] |
Wednesday, March 12, 2008 3:42PM - 3:54PM |
S30.00007: Heat flow in metallic carbon nanostructures: hot phonons or hot electrons? Marcelo Kuroda, Jean-Pierre Leburton A model for electronic and thermal transport in metallic carbon nanotubes and graphene ribbons under electrical stress is presented. The influence of acoustic and optical phonon scattering is taken into account within a self-consistent electro-thermal scheme. Owing to the linear electronic dispersion relation, two thermalized carrier populations arise as a consequence of inter-carrier scattering. We show that depending on the experimental setup and nanotube parameters, different transport regimes emerge for which non-equilibrium electrons and phonons compete to carry the energy in these carbon nanostructures. [Preview Abstract] |
Wednesday, March 12, 2008 3:54PM - 4:06PM |
S30.00008: A first principles approach for thermal transport in nanostructures with defects Derek Stewart, Ivana Savic, Natalio Mingo Efficient heat transport is essential for developing viable nanoscale devices. On these small scales, defects, impurities, and even isotopic composition can dramatically affect thermal transport in heat conduits such as nanowires and nanotubes. We present a first principles approach that combines a non-equilibrium Green's function formalism for thermal transport with interatomic force constants derived from density functional calculations. We apply this approach to examine the thermal conductance in several potential heat conduits such as carbon nanotubes, boron nitride nanotubes, and silicon based nanowires. These nanostructures are treated in terms of a central region linked to two semi-infinite leads and interatomic force constants are calculated for the three separate regions. The role of defects on thermal conductance is examined for the different devices and the results are compared to empirical potential calculations and commonly used analytical models. [Preview Abstract] |
Wednesday, March 12, 2008 4:06PM - 4:18PM |
S30.00009: Thermal and transport properties of a single nickel nanowire Min-Nan Ou, Yang-Yuan Chen, Maw-Kuen Wu, Tzong-Jer Yang, P. C. Lee, S. R. Harutyunyan, C. D. Chen, S. J. Lai Starting with a 100 nm nickel film grown on a Si$_{3}$N$_{4}$/Si substrate by thermal evaporator, a suspended nickel nanowire (Ni-NW) was fabricated through e-beam lithography and etching processes. The Ni-NW was a part of 4-probes circuit which is designed for electrical, thermal and thermopower measurements. The resistivity (\textit{$\rho $}) and thermal conductivity (\textit{$\kappa $}) of a single nickel nanowire have been measured in the temperature range from 4 to 300 K by 4-probes method and the self-heating-3$\omega $ technique. At 300 K the thermal conductivity of nanowire is $\sim $ 20{\%} of the bulk, it diminishes to lower value as temperature decreases, the consequence is opposite to that in the bulk in which it decreases with temperature increase. The result might be explained by the restriction of mean free paths of electron/phonon--phonon interactions due to the grain boundaries. The small relative resistivity ratio (RRR $\sim $ 2) confirms the polycrystalline characteristic of the nanowire. The thermopower (Seedbeck coefficient $S)$ was also investigated by temperature gradient built up between two ends of the nanowire. The figure of merit ZT=S$^{2}\sigma $/$\kappa $ in the one-dimension specimen will be discussed. [Preview Abstract] |
Wednesday, March 12, 2008 4:18PM - 4:30PM |
S30.00010: Microwave Kinetic Inductance Measurement of a Carbon Nanotube Y. Yin, J. Chudow, D.F. Santavicca, V. Manucharyan, A.J. Annunziata, L. Frunzio, D.E. Prober, B. Reulet, A. True, C.A. Schmuttenmaer, M. Purewal, Y. Zuev, P. Kim The single-wall metallic carbon nanotube is a model molecular nano-system, and has also been proposed as a candidate for future IC interconnects. For both these reasons, measurement of the kinetic inductance is desirable. This inductance arises from the kinetic energy of electrons in the four quantum channels. It is a fundamental prediction of the Luttinger liquid theory. Direct measurements at room temperature have been reported by Intel. That measurement is very challenging due to the large resistance compared to 50 ohms, and the small inductive impedance. We propose and demonstrate a new approach which uses two on-chip transmission line resonators to transform the nanotube impedance to nearly match the 50 ohm range of the microwave network analyzer. Simulations and cryogenic measurements will be presented. [Preview Abstract] |
Wednesday, March 12, 2008 4:30PM - 4:42PM |
S30.00011: Effects of Confinement Potential and Screening on a Quasi One Dimensional Electron Gas Luke Shulenburger, MIchele Casula, Gaetano Senatore, Richard M. Martin We study a quasi one dimensional system of electrons for different densities and strengths of the transverse confining potential. By means of exact quantum Monte Carlo techniques, we analyze the behavior of electrons interacting via an unscreened potential with a long range $1/r$ tail. We also study the effect of screening due to a metallic gate, which allows a more direct comparison with experiments. \vskip 0.1cm While the high density regime is well described by the RPA, we find that the charge compressibility $\chi_c$ is reduced due to electronic correlation as the density decreases. In the absence of screening, this corresponds to the onset of a quasi Wigner crystal, as shown by the finite size scaling of the static structure factor at 4k$_f$. As the density decreases further, the electrons behave as spinless fermions which is evidenced by the energetics and exponentially small spin velocities. The spinless fermion features persist also in the strongly screened system, and the RPA to Wigner crystal crossover is shifted to higher densities for a thinner wire. [Preview Abstract] |
Wednesday, March 12, 2008 4:42PM - 4:54PM |
S30.00012: Zone Unfolding and Approximate Bandstructure Calculations in Tight-Binding Timothy Boykin, Neerav Kharche, Mathieu Luisier, Gerhard Klimeck Tight-binding electronic structure calculations for periodic systems are often carried out in non-primitive unit cells, or for imperfect (e.g. random-alloy) nanostructures, such as nanowires. In the first case bands exist but they are difficult to identify due to the choice of unit cell for the calculation, while in the second case bands only exist in an approximate sense. The Brillouin zone unfolding technique applied to tight-binding calculations provides a powerful tool for extracting the true primitive-cell bands from non-primitive cells. Also, it is the starting point for approximate nanowire band calculations. We discuss zone unfolding in tight-binding and its application to both perfect and imperfect systems. [Preview Abstract] |
Wednesday, March 12, 2008 4:54PM - 5:06PM |
S30.00013: Gate Voltage Dependent Raman Scattering from Semiconducting Carbon Nanotube FETs James Tsang, Marcus Freitag, Vasili Perebeinos, Phaedon Avouris The Raman spectrum of the carbon nanotube in a carbon nanotube FET changes reversibly as a gate voltage is applied, modifying the charge density in the channel. We show that the intensity of the G-line Raman scattering from semiconducting CNTFETs can decrease with applied gate voltage. This is in addition to our previously reported shift of the G-line to higher energies with no change in spectral width as the channel charge density increases. The spectral shift been explained by gate voltage induced changes in the electronic excitations of the carbon nanotube which interact with the G-line. The gate voltage induced G-line shift and intensity changes observed in CNTFETs are similar to the changes observed for the G-line scattering between a suspended carbon nanotube over a trench, and the same tube on the substrate, where the G-line scattering from tube on the substrate shifts to higher energies and is weaker than the G-line scattering from the suspended tube. Gate voltage or substrate induced doping effects can modify the measured intensity of the Raman spectrum of a semiconducting carbon nanotube. [Preview Abstract] |
Wednesday, March 12, 2008 5:06PM - 5:18PM |
S30.00014: Directed Assembly and Electrical Characterization of Carbon Nanotube-Molecule-Metal Junctions Kansheng Chen, P. Xiong, S.A. McGill Molecular-template directed assembly has been shown to be an effective method for bottom-up assembly of high-performance single-walled carbon nanotube field-effect transistors (SWNT-FETs) $^{1}$. Here, we utilize this platform to carry out a systematic study of the electron transport behavior through SWNT-molecule-metal junctions. The devices were fabricated on doped- Si/SiO$_{2}$ substrates: Au source/drain electrodes were first defined by electron beam lithography. Self-assembled monolayers (SAMs) of thiol molecules with polar ends were then created on both electrodes by immersing the sample in molecule solution or on one of the electrodes by dip-pen nanolithography. Finally, SWNTs were selectively self-assembled onto the electrodes by putting a drop of SWNT solution on the template. The electron transport through the molecular SAM between the SWNT(s) and the Au electrodes were characterized through gated I-V measurements. The same devices were measured before after the desorption of the molecular SAM(by baking) to directly elucidate the role of the molecules on the electron transport. The results will be presented and discussed. \newline $^{1}$S.A. McGill et al., Appl. Phys. Lett. \textbf{89}, 163123 (2006). [Preview Abstract] |
Wednesday, March 12, 2008 5:18PM - 5:30PM |
S30.00015: Thermal Imaging of Electrically-Heated Carbon Nanotubes using Raman Spectroscopy Scott Hsieh, Vikram Deshpande, Adam Bushmaker, Steve Cronin, Marc Bockrath Suspended carbon nanotubes have been known to exhibit striking negative differential conductance under high bias voltages$^{1}$. To better probe the physics underlying this phenomenon, we have recently developed techniques to measure Raman spectra simultaneously with electrical transport, resulting in the direct observation of mode selective electron-phonon coupling$^{2}$. Using similar techniques, we present spatially resolved data taken from long, suspended, and electrically contacted individual carbon nanotubes. Along with electrical transport, Raman spectra are taken at several points along the spatial coordinate, creating a spatial map of the Raman-active phonon populations and the lattice temperature profile. We use a finite element simulation to corroborate our data with a Landauer model and extract numerical values for key scattering and relaxation rate parameters and thermal contact resistances. This use of Raman spectroscopy constitutes a novel non-contact technique for probing local thermal data in nanostructures. \newline $^{1}$ Pop \textit{et al., Phys. Rev. Lett.} (2005). \newline $^{2}$ Bushmaker \textit{et al., Nano Lett.} (2007). [Preview Abstract] |
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