Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session L30: Metallic and Semiconducting Nanotubes |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Alex Efros, Naval Research Laboratory Room: Morial Convention Center 222 |
Tuesday, March 11, 2008 2:30PM - 2:42PM |
L30.00001: Surface scattering in metallic nanowires Xi Chen, Randall Victora We theoretically study the electronic transport with surface scattering in metallic nanowires. The Landauer formula along with a recursive Green's function technique is employed to calculate the transport properties of wires with surface disorder. In the diffusive regime, the resistance increases linearly with the wire length, with a slope determined by the elastic mean free path (MFP). For strong scattering, MFP grows linearly with the wire diameter in a way that violates the semi-classical Fuchs-Sondheimer model. The mechanism for the violation is discussed. In the weak scattering limit, MFP grows with the diameter in an oscillatory manner owing to the quantum size effect. We propose an analytical theory that explains the observed behavior. The MFP is also shown to strongly depend on the surrounding environment of the nanowire. For wires with realistic sizes, we quantitatively show that the surface scattering alone can cause a resistivity that is several times larger than the bulk value. This work is supported by the National Science Foundation under Award Number ECS-0621868 and by the University of Minnesota Supercomputing Institute. [Preview Abstract] |
Tuesday, March 11, 2008 2:42PM - 2:54PM |
L30.00002: Phonon mode and Breakdown of a Au nanowire between electrodes Liqin Ke, Mark Van Schilfgaarde The deformation behavior of an atomic Au wire placed between Au electrodes, was investigated by using a generalization of the method of linear muffin-tin orbitals (LMTO) within the local-density approximation (LDA). We studied the dynamical motion of the atoms in the wire. Soft phonon modes were studied. It has been found that the lowest phonon eigenstate are associated with motions of atom in the middle of the chain. Atomic motion of this mode was studied by solving the muclear wavefunction of this atom. The quantum and classical effects are compared. At certain stages of the wire breaking process, atomic fluctuations become very large. We also show that the wire conductance is sensitive to the details of the deformation, which implies that the intrinsic noise in the conductance is of the order as the conductance itself. Large displacements which resulted in wire breakage were also studied. The energy barrier associated with this process has been calculated. [Preview Abstract] |
Tuesday, March 11, 2008 2:54PM - 3:06PM |
L30.00003: Semiconducting chains of gold and silver Ricardo Nunes, Frederico Fioravante The authors introduce a geometry for ultrathin Au and Ag wires that {\it ab initio} calculations indicate to be more stable than previously considered planar zigzag geometries for these systems, by about 0.1 eV per atom. This structure is insulating for both metals and for related Ag$_{0.5}$Au$_{0.5}$ alloys, with gaps of 1.3 eV for Au, 0.8 eV for Ag, and varying between 0.1 eV and 1.9 eV for the alloys. The insulating nature of the geometry is not a result of Peierls instabilities, and is analyzed in terms of an interplay between geometric and electronic structure effects. [Preview Abstract] |
Tuesday, March 11, 2008 3:06PM - 3:18PM |
L30.00004: Bonding, Conductance and Magnetization of Oxygenated Au Nanowires Chun Zhang, Robert Barnett, Uzi Landman Spin-density-functional calculations of tip-suspended gold chains, with molecular oxygen, or dissociated oxygen atoms, incorporated in them, reveal structural transitions for varying lengths. The nanowires exhibit enhanced strength for both oxygen incorporation modes, and upon stretching tip atoms join the wire. With incorporated molecular oxygen the wire conductance is about 1(2e$^{2}$/h), transforming to an insulating state beyond a critical length. The nanowire conductance with embedded oxygen atoms is low, 0.2 (2e$^{2}$/h), and it develops magnetic moments localized on the oxygens and the neighboring Au atoms. \textbf{Physical Review Letters (in press)} [Preview Abstract] |
Tuesday, March 11, 2008 3:18PM - 3:30PM |
L30.00005: ABSTRACT WITHDRAWN |
Tuesday, March 11, 2008 3:30PM - 3:42PM |
L30.00006: Superconductivity and metal-insulator transition in Bi nanowires. Mingliang Tian, Jian Wang, Nitesh Kumar, Qi Zhang, Thomas Mallouk, Jianendra Jain, Moses H.W. Chan Semi-metallic bismuth has long been a prototype system for quantum transport and finite-size effect studies, due to its long electron mean-free path, low carrier density and small carrier mass. We found Bi nanowires (NWs) of less than 100 nm diameter can be superconducting, metallic and insulating closely depending on the details of their microstructures, morphology and surface condition. For granular Bi NWs with grains showing (001) preferred orientation, the NWs are superconducting with Tc's of 7.2 and 8.3 K. Without (001) preferred orientation, the NWs show superresistive behavior. For single-crystalline Bi NWs, when the wires are embedded inside anodized aluminum oxide (AAO) membrane, insulating behavior is found below 1.0 K with low excitation current but metallic at a higher bias current. However, this metallic state can be tuned into insulating again by an applied magnetic field. We have also made measurements on an individual single-crystalline Bi NWs released from the AAO, an thin oxide layer is found on the wire surface. Interestingly, the wire was found to be superconducting below 1.5 K. [Preview Abstract] |
Tuesday, March 11, 2008 3:42PM - 3:54PM |
L30.00007: Evolution of Integer Quantized Conductance in Gold Nnowires Yoshihiko Kurui, Yoshifumi Oshima, Masakuni Okamoto, Kunio Takayanagi Conductance of gold junction was measured during many breaking procedures, while simultaneously acquiring transmission electron microscope images. The conductance histogram exhibits the quantized peaks in the vicinity of $G_{0 }$(=2e$^{2}$/h: conductance quantum), 2$G_{0}$, 3$G_{0}$, and 4$G_{0}$. From the TEM images, we found that these values correspond to single, double, triple and quadric atomic strands, respectively. With the exception of the quadric strand, these strands were arranged in a planar sheet with a ladder or zigzag configuration that respectively resembled the (001) and (111) lattice planes of the gold crystal. [Preview Abstract] |
Tuesday, March 11, 2008 3:54PM - 4:06PM |
L30.00008: Intrinsic Electrical-Transport Properties of Single ZnO Nanowires S.P. Chiu, Y.H. Lin, J.J. Lin, W.B. Jian, Z.Y. Wu, F.R. Chen, J.J. Kai Single-crystalline zinc oxide (ZnO) nanowires (NWs) were synthesized by the thermal evaporation method. The intrinsic electrical-transport properties of ZnO NWs were studied by carrying out four-probe measurements on individual NWs. The electrodes were made by the standard electron-beam lithography technique. The current-voltage characteristics and the zero-bias resistivities, \textit{$\rho $}(T), were measured over a wide range of temperatures between 0.25 and 300 K. We found that, in many cases, the temperature behavior of \textit{$\rho $} could be well-described by the thermal-activation model involving three activation energies ($E_{1}$, $E_{2}$ and $E_{3})$. Our values of $E_{1}$ (approximately, several tens meV) extracted from the \textit{$\rho $}(T) around 300 K are close to the ionization energies of the major known shallow donors in ZnO. Our values of $E_{2}$ (approximately, several meV) extracted from the \textit{$\rho $}(T) in the intermediate temperature regime might originate from electron activation from the lower impurity band to the upper Hubbard subband ($D^{-}$ band). Finally, at very low temperatures ($<$ 5 K), the measured \textit{$\rho $}(T) indicated diminishing values of $E_{3}$ (approximately, thousandths meV), suggesting essentially metallic behavior. [Preview Abstract] |
Tuesday, March 11, 2008 4:06PM - 4:18PM |
L30.00009: Electrical-transport studies of individual RuO$_2$ nanowires and their nanowire contacts Y.H. Lin, K.J. Lin, F.R. Chen, J.J. Kai, J.J. Lin Single-crystalline RuO$_2$ nanowires (NWs) have been prepared by the thermal evaporation method. With the help of e-beam lithography, individual NWs were contacted by submicron electrodes from above. By employing 4- and 2-probe configurations, not only the intrinsic electrical resistivities of the NWs but also the electronic contact resistances, $R_{\mathrm{c}}(T)$, have been determined. Our measured resistivity behavior of the NWs is found to agree well with the current understanding of this rutile material within the framework of the Boltzmann transport theory. On the other hand, we found that, for high-resistance contacts, $R_{\mathrm{c}}$ increases rapidly with decreasing temperature and finally saturates at liquid-helium temperatures. This behavior of $R_{\mathrm{c}}$ can be satisfactorily explained in terms of the ``thermally fluctuation-induced tunneling'' conduction through a microscopic junction incidentally formed at the interface between the electrode and the NW. [Preview Abstract] |
Tuesday, March 11, 2008 4:18PM - 4:30PM |
L30.00010: Anomalous Long-Range Proximity Effect in Template-Fabricated Single-Crystal Superconducting Nanowires Wenhao Wu, Haidong Liu, Zuxin Ye, Zhiping Luo, K. D. D. Rathnayaka We report an anomalous proximity effect observed in single-crystal nanowires of Zn, Sn, and Pb of length up to 60 $\mu $m. These nanowires were electrochemically deposited into the pores of anodic aluminum oxide membranes and polycarbonate membranes. Using an \textit{in situ} self-contacting method, single nanowires were electrically contacted on both ends to a pair of macroscopic film electrodes of Au, Sn, and Pb pre-fabricated on both surfaces of the membranes. We observed that superconductivity in the nanowires was strongly suppressed when Au electrodes were used. When superconducting electrodes with higher transition temperatures were used, the nanowires became superconducting at the transition temperatures of the electrodes. We will present measurements of the sample resistance and the $I-V$ characteristics at various temperatures and magnetic fields. Scanning electron microscopy and transmission electron microscopy analyses of the structure and the composition of the nanowires will also be presented. [Preview Abstract] |
Tuesday, March 11, 2008 4:30PM - 4:42PM |
L30.00011: Electronic Transport of TiO$_{2}$ Nanowire Devices Geetha Dholakia, Steven Kuo, Emily Allen Titanium dioxide (TiO$_{2})$ is a wide band-gap semiconductor with applications in photovoltaics and sensing. Large scale integration of nanowires onto functional devices requires new techniques to manipulate them at the nanoscale. Currently engineering strategies for efficient assembly of nanoscale objects is very limited. Here we report the use of dielectrophoresis to assemble TiO$_{2}$ nanowires onto devices. We use a sol-gel template based synthesis of TiO$_{2}$ nanowires. The nanowires have typical diameters of 100-150 nm and range in length from 3-10 $\mu $m. Devices for two probe and four probe measurements were fabricated by standard lithography. AC dielectrophoresis was used to assemble the TiO$_{2}$ nanowires on devices. A dielectrophoretic translational force and a torque aligns the nanowires onto the devices. FIB assisted platinum deposition on the aligned TiO$_{2}$ nanowires ensures ohmic contacts. Two probe room temperature I-V measurements show a resistivity of 0.22 $\Omega $-cm, which is comparable to 0.26 $\Omega $-cm for a thin film$^{1}$. Temperature dependent transport measurements are being pursued. We have demonstrated an efficient method of assembling and fabricating nanowire device structures. T. Miyata et. al. Thin Solid Films, \textbf{496}, 136 (2006). [Preview Abstract] |
Tuesday, March 11, 2008 4:42PM - 4:54PM |
L30.00012: Conductivity of MgZnO nanoparticles as a function of gas exposure and temperature Chris Berven, Joseph Dick, Leah Bergman, Jesse Huso, John Morrison Changes in the current-voltage (I-V) characteristics of Mg$_{x}$Zn$_{1-x}$O (x = 0.15) nanoparticles as a function gas exposure and temperature are reported. The nanoparticles were prepared using wet chemical techniques on insulating thermally grown SiO$_{x}$ Si substrates. Contact to the nanoparticle film was by gold wires laid across about 2 mm apart. The experiments were performed in a custom-built environmental chamber with the ability to evacuate or introduce various gases. For these experiments, the temperature was tuned over a range of about 300 K to 420 K. Our measurements showed a possible history-dependant behavior in changes of the conductance of the nanoparticle film. When the device was heated to $\sim $120 K in vacuum or in an Ar the current increased by the same amount. When repeated with H$_{2}$, the current increase was less. Initially, the effect was quite pronounced with a relative change by a factor of 20. With repetitions of the experiments, the same effect was observed but to a lesser degree suggesting a saturation phenomena. When the experiment was modified so that the H$_{2}$ gas was introduced at a high temperature to an evacuated chamber the current dropped but not by the same degree as before. A similar response to exposure to H$_{2}$ was found for exposure to O$_{2}$. Possible explanations for the observations will be presented. [Preview Abstract] |
Tuesday, March 11, 2008 4:54PM - 5:06PM |
L30.00013: Noise Characterization of Semiconductor Nanowires C.A. Richter, H.D. Xiong, V.M. Stanford, Wenyong Wang, Xiaoxiao Zhu, Qiliang Li, Woong-Ki Hong, Takhee Lee A thorough understanding of the noise properties of emerging nanoelectronic devices such as those based on semiconductor nanowires is critical because the signal-to-noise ratio is a fundamental factor limiting their performance. We present the systematic characterization of the low frequency noise properties of Si and ZnO semiconductor nanowire field effect transistors. At room temperature, the noise power spectra have a classic 1/f dependence while random telegraph signals (RTS's) are observed in the drain current at 4.2 K leading to a Lorentzian type noise spectra. The RTS's are characterized by estimating a hidden Markov model based on a Gaussian mixture, and quantified using a Viterbi decoder to measure the discrete current switching events. This analysis enables the estimation of parameters such as event lifetime, event amplitudes, and trap cross-section. Under some conditions, three-level switching is observed that can be attributed to two near-interface oxide traps. These data illustrate that the characterization of two- and multi-level RTS's is a valuable tool to determine the energetic and spatial position of individual defects in semiconductor nanoelectronic devices. [Preview Abstract] |
Tuesday, March 11, 2008 5:06PM - 5:18PM |
L30.00014: Remarkable Effects of Gating on the Photoconductivity of Porphyrin Nanorods C. K. Riley, X. Huang, W. F. Smith, D. E. Johnston, A. T. Johnson Tetrakis(4-sulfonatophenyl) porphine self assembles into well-defined nanorods with intriguing photoelectronic properties.$^{1}$ For example, when light is applied, the conductivity immediately jumps up from zero, then grows further over several hours. This may be due to a light-induced structural change. In recent experiments, we imaged the nanorods with AFM while measuring the photoconductivity; we observed no change in morphology. We also deposited nanorods onto oxidized silicon substrates. We find that the photoconductivity is not sensitive to the \underline {value} of the gate voltage applied to the underlying silicon, but only to \underline {changes} in the gate voltage. The photoconductivity increases when the gate voltage is increased, but then relaxes back to its original level over about one hour. When the gate voltage is decreased, the photoconductivity decreases, and again slowly relaxes back. These results may be associated with structural changes caused by the electric field of the gate, which may affect filling of trap states. $^{1}$A.D. Schwab \textit{et al.}, Nano Letters \textbf{4}, 1261 (2004). [Preview Abstract] |
Tuesday, March 11, 2008 5:18PM - 5:30PM |
L30.00015: Adsorption Kinetics of Alkanes on Purified HiPco Nanotubes Dinesh Rawat, Murat Bulut, Aldo Migone We present results for the adsorption kinetics of methane, ethane and butane on purified HiPco SWNTs. We studied the adsorption kinetics by monitoring the evolution of the gas pressure with time from the instant at which a dose of adsorbate is added to the sample, until the moment at which equilibrium is reached. The waiting times for comparable coverages increase with increasing alkane chain length. For methane and ethane, the equilibration time decreases with increasing fractional coverage. For the butane, on the other hand, the kinetic measurements display a reverse trend: the equilibration times increase with increasing fractional coverage. We speculate that this observed increase in the waiting time is due to a possible reorientation of adsorbed molecules in the film. The observed differences in adsorption kinetics suggest the possibility of using adsorption as a means to achieve the separation of gaseous alkane mixtures. [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. |
© 2024 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