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Klein-tunneling transistor with ballistic graphene  [PDF]
Quentin Wilmart,Salim Berada,David Torrin,V. Hung Nguyen,Gwendal Fève,Jean-Marc Berroir,Philippe Dollfus,Bernard Pla?ais
Physics , 2014,
Abstract: Today the availability of high mobility graphene up to room temperature makes ballistic transport in nanodevices achievable. In particular, p-n-p transistor in the ballistic regime gives access to the Klein tunneling physics and allows the realization of devices exploiting the optics-like behavior of Dirac Fermions (DF) as in the Vesalego lens or the Fabry P\'erot cavity. Here we propose a Klein tunneling transistor based on geometrical optics of DF. We consider the case of a prismatic active region delimited by a triangular gate, where total internal reflection may occur, which leads to the tunable suppression of the transistor transmission. We calculate the transmission and the current by means of scattering theory and the finite bias properties using Non Equilibrium Green's Function(NEGF) simulation.
Ballistic transport and boundary scattering in InSb/InxAl1-xSb mesoscopic devices  [PDF]
A. M. Gilbertson,M. Fearn,A. Kormányos,D. E. Read,C. J. Lambert,M. T. Emeny,T. Ashley,S. A. Solin,L. F. Cohen
Physics , 2010,
Abstract: We describe the influence of hard wall confinement and lateral dimension on the low temperature transport properties of long diffusive channels and ballistic crosses fabricated in an InSb/InxAl1-xSb heterostructure. Partially diffuse boundary scattering is found to play a crucial role in the electron dynamics of ballistic crosses and substantially enhance the negative bend resistance. Experimental observations are supported by simulations using a classical billiard ball model for which good agreement is found when diffuse boundary scattering is included.
Ballistic transport at room temperature in micrometer size multigraphene  [PDF]
S. Dusari,J. Barzola-Quiquia,P. Esquinazi,N. García
Physics , 2010, DOI: 10.1103/PhysRevB.83.125402
Abstract: The intrinsic values of the carriers mobility and density of the graphene layers inside graphite, the well known structure built on these layers in the Bernal stacking configuration, are not well known mainly because most of the research was done in rather bulk samples where lattice defects hide their intrinsic values. By measuring the electrical resistance through microfabricated constrictions in micrometer small graphite flakes of a few tens of nanometers thickness we studied the ballistic behavior of the carriers. We found that the carriers' mean free path is micrometer large with a mobility $\mu \simeq 6 \times 10^6 $cm$^2$/Vs and a carrier density $n \simeq 7 \times 10^8 $cm$^{-2}$ per graphene layer at room temperature. These distinctive transport and ballistic properties have important implications for understanding the values obtained in single graphene and in graphite as well as for implementing this last in nanoelectronic devices.
Coherent spin transport and suppression of spin relaxation in InSb nanowires with single subband occupancy at room temperature  [PDF]
Saumil Bandyopadhyay,Md. Iftekhar Hossain,Hasnain Ahmad,Jayasimha Atualsimha,Supriyo Bandyopadhyay
Physics , 2014, DOI: 10.1002/smll.201401022
Abstract: A longstanding goal of spintronics is to inject, coherently transport, and detect spins in a semiconductor nanowire where a SINGLE quantized subband is occupied at room temperature. Here, we report achieving this goal in 50-nm diameter InSb nanowires by demonstrating both the spin-valve and the Hanle effect. The spin relaxation time in the nanowires was found to have increased by an order of magnitude over what has been reported in bulk and quantum wells due to the suppression of D'yakonov-Perel' spin relaxation as a result of single subband occupancy. These experiments raise hopes for the realization of a room-temperature Datta-Das spin transistor.
Carbon nanotubes: Ballistic transport or room-temperature superconductivity?  [PDF]
Guo-meng Zhao
Physics , 2002,
Abstract: We theoretically estimate the electron-phonon coupling constant lambda for metallic single-walled carbon nanotubes with a diameter of 1.4 nm. The partial electron-phonon coupling constant for the hardest phonon mode is estimated to be about 0.0036, in good agreement with that deduced from Raman scattering data assuming superconductivity above room temperature. Assuming no superconductivity, we estimate the room-temperature inelastic mean free path l_ep due to electron-phonon scattering to be about 0.46 micrometer, and the total room-temperature inelastic mean free path l_in to be about 0.16 micrometer. We then argue that the electrical transport data of individual multi-walled nanotubes cannot be explained by ballistic transport at room temperature but provide strong evidence for quasi-one-dimensional superconductivity above room temperature.
Room Temperature Ballistic Conduction in Carbon Nanotubes  [PDF]
Philippe Poncharal,Claire Berger,Yan Yi,Z. L. Wang,Walt A. de Heer
Physics , 2002,
Abstract: Multiwalled carbon nanotubes are shown to be ballistic conductors at room temperature, with mean free paths of the order of tens of microns. These experiments follow and extend the original experiments by Frank et al (Science, 280 1744 1998) including in-situ electron microscopy experiments and a detailed analysis of the length dependence of the resistance. The per unit length resistance r < 100 Ohm/micron, indicating free paths l > 65 microns, unambiguously demonstrate ballistic conduction at room temperature up to macroscopic distances. The nanotube-metal contact resistances are in the range 0.1-1 kOhm micron. Contact scattering can explain why the measured conductances are about half the expected theoretical value of 2 G0 . For V>0.1V the conductance rises linearly (dG/dV~0.3 G0 /V) reflecting the linear increase in the density-of-states in a metallic nanotube above the energy gap. Increased resistances (r =2- 10 k Ohm/micron) and anomalous I-V dependences result from impurities and surfactants on the tubes.Evidence is presented that ballistic transport occurs in undoped and undamaged tubed for which the top layer is metallic and the next layer is semiconducting. The diffusive properties of lithographically contacted multiwalled nanotubes most likely result from purification and other processing steps that damage and dope the nanotubes thereby making them structurally and electronically different than the pristine nanotubes investigated here.
Micrometer-scale ballistic transport in encapsulated graphene at room temperature  [PDF]
A. S. Mayorov,R. V. Gorbachev,S. V. Morozov,L. Britnell,R. Jalil,L. A. Ponomarenko,P. Blake,K. S. Novoselov,K. Watanabe,T. Taniguchi,A. K. Geim
Physics , 2011, DOI: 10.1021/nl200758b
Abstract: Devices made from graphene encapsulated in hexagonal boron-nitride exhibit pronounced negative bend resistance and an anomalous Hall effect, which are a direct consequence of room-temperature ballistic transport on a micrometer scale for a wide range of carrier concentrations. The encapsulation makes graphene practically insusceptible to the ambient atmosphere and, simultaneously, allows the use of boron nitride as an ultrathin top gate dielectric.
Geometrical-induced rectification in two-dimensional ballistic nanodevices  [PDF]
Daniela Dragoman,Mircea Dragoman
Physics , 2012, DOI: 10.1088/0022-3727/46/5/055306
Abstract: The paper demonstrates that a two-dimensional ballistic nanodevice in which the electron gas satisfies either the Schroodinger equation (as in quantum wells in common semiconductor heterostructures) or the Dirac equation (as in graphene) is able to rectify an electric signal if the device has a non-uniform cross section, for instance a taper configuration. No p-n junctions or dissimilar electrodes are necessary for rectification.
Room Temperature Device Performance of Electrodeposited InSb Nanowire Field Effect Transistors  [PDF]
Suprem R. Das,Collin J. Delker,Dmitri Zakharov,Yong P. Chen,Timothy D. Sands,David B. Janes
Physics , 2011, DOI: 10.1063/1.3587638
Abstract: In this study, InSb nanowires have been formed by electrodeposition and integrated into NW-FETs. NWs were formed in porous anodic alumina (PAA) templates, with the PAA pore diameter of approximately 100 nm defining the NW diameter. Following annealing at 125C and 420C respectively, the nanowires exhibited the zinc blende crystalline structure of InSb, as confirmed from x-ray diffraction and high resolution transmission electron microscopy. The annealed nanowires were used to fabricate nanowire field effect transistors (NW-FET) each containing a single NW with 500 nm channel length and gating through a 20nm SiO2 layer on a doped Si wafer. Following annealing of the NW-FETs at 300C for 10 minutes in argon ambient, transistor characteristics were observed with an ION ~ 40 uA (at VDS = 1V in a back-gate configuration), ION/IOFF ~ 16 - 20 in the linear regime of transistor operation and gd ~ 71uS. The field effect electron mobility extracted from the transconductance was ~1200 cm2 V-1 s-1 at room temperature. We report high on-current per nanowire compared with other reported NW-FETs with back-gate geometry and current saturation at low source-drain voltages. The device characteristics are not well described by long-channel MOSFET models, but can qualitatively be understood in terms of velocity saturation effects accounting for enhanced scattering
Room temperature-synthesized vertically aligned InSb nanowires: electrical transport and field emission characteristics
Cheng-Hsiang Kuo, Jyh-Ming Wu and Su-Jien Lin
Nanoscale Research Letters , 2013, DOI: 10.1186/1556-276X-8-69
Abstract: Vertically aligned single-crystal InSb nanowires were synthesized via the electrochemical method at room temperature. The characteristics of Fourier transform infrared spectrum revealed that in the syntheses of InSb nanowires, energy bandgap shifts towards the short wavelength with the occurrence of an electron accumulation layer. The current–voltage curve, based on the metal–semiconductor–metal model, showed a high electron carrier concentration of 2.0 × 1017 cm 3 and a high electron mobility of 446.42 cm2 V 1 s 1. Additionally, the high carrier concentration of the InSb semiconductor with the surface accumulation layer induced a downward band bending effect that reduces the electron tunneling barrier. Consequently, the InSb nanowires exhibit significant field emission properties with an extremely low turn-on field of 1.84 V μm 1 and an estimative threshold field of 3.36 V μm 1.
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