Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session V11: Transport Phenomena and Electronic Properties of Nanostructures |
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Sponsoring Units: DCMP Chair: Luis da Silva, Oak Ridge National Laboratory Room: 305 |
Thursday, March 19, 2009 8:00AM - 8:12AM |
V11.00001: Momentum statistics of tunneling electrons in nanoelectromechanical systems Steven D. Bennett, Aashish A. Clerk When a mesoscopic conductor is used to measure the position of a nanomechanical oscillator, electrons in the conductor exert a fluctuating back-action force on the oscillator. What is the statistical distribution of the momentum transferred to the oscillator by this force? Motivated by recent experiments that studied a mechanical oscillator coupled to a single tunnel junction \footnote{N. E. Flowers-Jacobs {\it et al.}, Phys. Rev. Lett. {\bf 98}, 096804 (2007).} or a quantum point contact \footnote{M. Poggio {\it et al.}, Nat. Phys. {\bf 4}, 635 (2008).}, we investigate theoretically the statistics of back-action force in these systems as well as correlations between the force and the current. Our approach is based on a scattering matrix that depends parametrically on the oscillator position, allowing us to go beyond weak tunneling and study conductors with arbitrary transmission. We identify two mechanisms of momentum transfer: one involves forces exerted in the scattering region and dominates in the limit of weak tunneling; the other is associated with transferred electron momentum and dominates in the limit of perfect transmission. We also discuss the effects of a spatially asymmetric conductor on the force noise and on the quantum limit of position detection. [Preview Abstract] |
Thursday, March 19, 2009 8:12AM - 8:24AM |
V11.00002: Mechano-electronic Superlattices in Silicon Nanoribbons M. Huang, C.S. Ritz, B. Novakovic, F. Flack, D.E. Savage, P.G. Evans, I. Knezevic, D. Yu, Y. Zhang, F. Liu, M.G. Lagally Single-crystal silicon nanomembranes (SiNMs) have the mechanical compliance fundamentally different from bulk materials or supported thin films that can produce unique structural and electronic effects. The growth of nanostressors on SiNMs utilizes this mechanical compliance to create a ``strain lattice'' consisting of tiny regions of local curvature in the SiNMs, the order occurring because the locally bending SiNMs provides a strong feedback for self-organization of the nanostressors. We demonstrate that a high degree of order occurs when Ge or SiGe nanostressors are grown on both sides of free-standing but end-tethered Si nanoribbons. Our calculations prove that the strain lattice in the Si produces a modulation in the electronic band structure, and thus an electronic superlattice. Our calculations also demonstrate that discrete minibands can be observable in such an electronic superlattice at 77K. It is expected that an electric conductivity will be increased in the superlattice. We predict that it is possible to observe discrete minibands at room temperature if other nanostressors are used. [Preview Abstract] |
Thursday, March 19, 2009 8:24AM - 8:36AM |
V11.00003: `Spring-Like' and Photo-actuated Molecular-Junctions between Nanoparticles Kabeer Jasuja, Vikas Berry Here we present a study on (1) ``molecular-spring'' nano-device, where controllable and confined forces are applied on collective molecular-junctions between nanoparticles and (2) photo-actuated nano-junction system where azo-molecules incorporated between nanoparticles apply confined forces to displace them. Both systems are built by using covalently/electrostatically crosslinked polyelectrolyte (cPE) molecules sandwiched between gold nanoparticles (GNP), where cPE molecular-junctions are reversibly compressed and stretched by applying electrically and centrifugally induced forces respectively. The GNPs play a dual role (a) of movable connectors to apply forces and (b) of nanoelectrodes to measure molecular deformation via electron tunneling change. The `molecular-spring' junctions were found to have a spring constant between 10$^{-4}$ to 10$^{-3}$ N/m depending on the thickness of the junction. We will also demonstrate the dynamics of these junctions via a motion-in-viscous-media model. The ability to store the compression energy in a molecular-device-architecture and to manipulate these by actuating junctions has the potential to power future molecular devices by stored molecular-energy and controlling properties of nanocomponent based devices. [Preview Abstract] |
Thursday, March 19, 2009 8:36AM - 8:48AM |
V11.00004: Noise characterization of metal oxide nanowire FETs with electronic properties controlled by surface geometry Wenyong Wang, Hao Xiong, Curt Richter, Woong-ki Hong, Takhee Lee In this talk we present the results of low-frequency noise and random telegraph signal (RTS) characterization of metal oxide nanowire (NW) field-effect transistors (FETs). ZnO nanowires with different surface geometry properties such as corrugated and smooth surfaces have been synthesized. FETs fabricated from these NWs exhibit different electronic transport characteristics. Noise characterization has been performed on NW FET devices with different surface properties. The obtained noise power spectra at room temperature show 1/f frequency dependences, and the Hooge's constants have been calculated from the gate voltage dependence fo the 1/f noise for the devices with different surface geometries. The characteristics of low frequency noise in the drain current have been further investigated through random telegraph signals measurements at 4.2 K, where the channel current RTSs can be attributed to the correlated carrier number and mobility fluctuation due to the trapping and detrapping of the carriers by discrete border/surface traps. The effects of the NW surface properties on the RTS behaviors will be discussed. [Preview Abstract] |
Thursday, March 19, 2009 8:48AM - 9:00AM |
V11.00005: A Biotransistor: Modulating the Current of a Nanodevice with a Living Cell Jennifer Kane, Jason Ong, Ravi Saraf Isolated single nanoparticles and array of nanoparticles act as switching devices sensitive to charging by a single electron. For a typical 5 nm Au particle, the switching barrier energy due to Coulomb blockade from a single electron charging is approximately 100 meV, making room temperature switching difficult and very noisy. In an array, the switching energy can be a few eV (at cryogenic temperatures), but unlike a single nanoparticle, the energy barrier reduces linearly and vanishes at room temperature. We have developed a ``reactive self-assembly'' method to make a network of one-dimensional necklaces of nanoparticles that behaves as a single-electron device at room temperature. Furthermore, upon cementing the particles with an inorganic semiconductor, the switching behavior at room temperature is significantly improved. To demonstrate an interesting application of room temperature single-electron switching, we couple the network to a living microorganism to modulate the device current by regulating the cell's metabolic activity. In the talk we will describe fabrication of the necklace and biotransistor device. [Preview Abstract] |
Thursday, March 19, 2009 9:00AM - 9:12AM |
V11.00006: ABSTRACT WITHDRAWN |
Thursday, March 19, 2009 9:12AM - 9:24AM |
V11.00007: ABSTRACT WITHDRAWN |
Thursday, March 19, 2009 9:24AM - 9:36AM |
V11.00008: Bistable tunneling current through a quantum dot array junction Yia-Chung Chang, David M.T. Kuo We investigate the tunneling current through a six-fold degenerate $p$ --like states of a one- dimensional (1D) or two-dimensional (2D) quantum dot (QD) array in the x-y plane. Due to the coupling of$p_x $ and $p_y $orbitals at neighboring QDs, a 1D or 2D conduction band ($\varepsilon _p )$ is formed, whereas the $p_z $ orbitals remain localized due to their weak in-plane coupling. The on-site repulsive Coulomb interaction in the $p_z $ levels ($U)$ and that between the $p_z $ level and $p_x $/$p_y $ level ($U_{dc} )$ are taken into account in an extended Anderson model, which is used to investigate the tunneling characteristics of the system. Tunneling current through localized $p_z $ state is calculated in the framework of the Green function technique. Due to the effect of $U_{dc} $, the 1D/2D conduction band states are shifted by a self-energy term $2NU_{dc} $. We find that bistable current can be observed for this system in the Coulomb blockade regime, which makes the system a valid candidate for ultra high-density memory device. [Preview Abstract] |
Thursday, March 19, 2009 9:36AM - 9:48AM |
V11.00009: Tunneling Between a Quantum Wire and a Two-Dimensional Electron Gas Dominique Laroche, John Reno, Guillaume Gervais, Mike Lilly We study 1D-2D tunneling between a quantum wire and a 2D electron gas as a function of magnetic field, source drain bias, temperature and 1D subband occupation. The transition from 2D-2D to 1D-2D tunneling is clearly observed through a sharpening of the tunneling resonance, confirming that the measurements are performed in a 1D-2D state. The device used is fabricated in a GaAs/AlGaAs parallel double quantum well heterostructure with an 11 nm wide Al$_{0.9}$GA$_{0.1}$As barrier separating the quantum wells. Quantum wires are created via electron beam lithography defined split gates fabricated on both sides of the sample, albeit only one of the wires is used in the experiment.. The design is such that the 1D density can be independently controlled over a large conduction range and is uniform over the length of the quantum wire. Both wires show non-ballistic quantum steps up until a conductance of 10 $\times $ 2e$^{2}$/h. Magnetotranpsport results are compared to tunneling in the 1D-1D and 2D-2D regimes. [Preview Abstract] |
Thursday, March 19, 2009 9:48AM - 10:00AM |
V11.00010: Temperature Dependence of Electron Tunneling between Quantum Dots and Electron Gas Yoko Sakurai, Shintaro Nomura, Yukihiro Takada, Kenji Shiraishi, Masakazu Muraguchi, Tetsuo Endoh, Mitsuhisa Ikeda, Katsunori Makihara, Seiichi Miyazaki We report that gate voltages required for electron injection to quantum dots (QDs) from electron gas and for emission from QDs strongly depend on temperature. For this experiment, Si-QDs floating gate MOS capacitors were designed and fabricated. Displacement current (I) was measured as a function of the gate voltage (V). Peaks in I-V curves appear as a result of charging and discharging of Si-QDs. We have found that the gate voltages for the electron injection to and for the emission from QDs shift toward more positive and negative values with decreasing temperature, respectively. Theoretical study predicts that electron tunneling is strongly enhanced when initial state of 2DES is localized below the QD [1]. Based on this discussion, the experimentally obtained results suggest that localization of electron gas induced by thermal fluctuation is responsible for enhanced electron tunneling. [Preview Abstract] |
Thursday, March 19, 2009 10:00AM - 10:12AM |
V11.00011: New insight into Tunneling Process between Quantum Dot and Electron Gas Masakazu Muraguchi, Tetsuo Endoh, Yoko Sakurai, Shintaro Nomura, Yukihiro Takada, Kenji Shiraishi, Mitsuhisa Ikeda, Katsunori Makihara, Seiichi Miyazaki, Yasuteru Shigeta We have theoretically investigated the time-evolution of electron wave function in tunneling from a two-dimensional electron gas (2DEG) to a quantum dot (QD). We have revealed that the electronic state in the electron gas significantly influences the electron tunneling. We clearly showed that the electron tunneling is modified depending on the initial electronic state in the 2DEG. The electron tunneling from 2DEG to QD is strongly enhanced when the initial state of the electron in the 2DEG is localized below the QD. This result indicates that the temporal and spatial fluctuation of electron distribution, which depends on temperature, plays a crucial role in the tunneling process. We will show that the obtained temperature dependence of electron tunneling coincides with our recent experiments of capacitance-voltage characteristic in a QD floating gate MOS capacitor. [Preview Abstract] |
Thursday, March 19, 2009 10:12AM - 10:24AM |
V11.00012: Hole Transport and Spin Effects in Cleaved-Edge-Overgrowth Quantum Wires Joseph Sulpizio, Charis Quay, Rafi de Picciotto, K.W. West, L.N. Pfeiffer, David Goldhaber-Gordon Transport measurements on ballistic GaAs electron wires have revealed a rich set of phenomena associated with one-dimensional (1D) quantum systems. Studies of transport in hole systems are a natural extension of these experiments due to the enhanced effective mass, g-factor, and spin-orbit coupling of holes over their electron counterparts. However, only recently has the creation of ballistic hole wire devices been possible due to breakthroughs in molecular beam epitaxy using the cleaved-edge-overgrowth (CEO) technique. We present measurements of hole transport in CEO GaAs quantum wires in magnetic field in a dilution refrigerator. Based on a simple model, we extract the g-factor for different field orientations, and also discuss evidence for observing spin-orbit coupling in a 1D system. [Preview Abstract] |
Thursday, March 19, 2009 10:24AM - 10:36AM |
V11.00013: High-quality quantum point contact in two-dimensional GaAs (311)A hole system Javad Shabani, Jason Petta, Mansour Shayegan We studied ballistic transport across a quantum point contact (QPC) defined in a high-quality, GaAs (311)A two-dimensional (2D) hole system using shallow etching and top-gating. The QPC conductance exhibits up to 11 quantized plateaus and the ``0.7'' structure. The ballistic one-dimensional subbands are tuned by changing the lateral confinement and the Fermi energy of the holes in the QPC. We demonstrate that the positions of the plateaus (in gate-voltage), the source-drain data, and the negative magneto- resistance data can be understood in a simple model that takes into account the variation, with gate bias, of the hole density and the width of the QPC conducting channel. Spacings between the quantized energy levels in this geometry are about 2 to 7 times larger than in previous reports of QPCs in other GaAs hole systems. [Preview Abstract] |
Thursday, March 19, 2009 10:36AM - 10:48AM |
V11.00014: ABSTRACT WITHDRAWN |
Thursday, March 19, 2009 10:48AM - 11:00AM |
V11.00015: Determination Hanbury-Brown Twiss correlations with electrons and photons Eva Zakka-Bajjani, J. Dufouleur, P. Roche, D.C. Glattli, F. Portier What is the statistics of the photons emitted by a quantum
conductor? We
present the first experiment addressing this question, where the
electronic
shot noise power of a 500$\Omega $ tunnel junction is measured in
the 4-8
GHz frequency range in an Hanbury-Brown Twiss geometry (E.
Zakka-Bajjani \textit{et al.}
Phys. Rev. Lett. \textbf{99}, 236803 (2007)). The emitted noise
is analyzed
in two different manners. The fluctuations of the transmitted and
reflected
electronic currents are shown to be anti-correlated. The
auto-correlated
power fluctuations reveal that the junction emits power into the
detection
in the form of photons, and the emitted powers show positive
cross-correlation, proportional to the squared emitted power. The
photons
emitted by a biased low impedance (i.e. R$_{tunnel}< |
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