Electron transport in nanoparticle single-electron transistors

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Title: Electron transport in nanoparticle single-electron transistors
Author: Luo, Kang, 1976-
Abstract: Electron transport in nanoparticle single -electron transistors (SETs ) is a fruitful method to explore a wide range of physical phenomena at the nanometer scale . In this thesis , we investigate electron transport in SETs incorporating various nanoparticles , including gold nanoparticles in both classical and quantum regimes and Pb nanoparticle in both superconducting and normal states . SETs have been successfully fabricated by incorporating individual gold nanoparticles into the gaps between two electrodes . Although single -electron tunneling behavior is prominent , quantized energy levels cannot be resolved in these SETs due to their relatively large particle sizes . A novel method has been developed to achieve SETs incorporating gold nanoparticles whose sizes are small enough to resolve discrete quantum energy levels . The devices consist of spontaneously -formed ultrasmall gold nanoparticles linked by alkanedithiols to gold electrodes . The devices reproducibly exhibit addition energies of a few hundred meV , which enables the observation of single electron tunneling at room temperature . At low temperatures , resonant tunneling through discrete energy levels in the Au nanoparticles is observed , which is accompanied by the excitations of molecular vibrations at large bias voltage . Having explored the SETs in normal state , we have extended the experiments to superconducting single -electron transistors (SSETs ) . We first fabricated and characterized Pb superconducting electrodes with nanometer -sized separation . Our observation clearly shows that conventional Barden -Cooper -Schrieffer theory remains valid to interpret the tunneling behavior between two nanometer -spaced Pb electrodes . Furthermore , by incorporating Pb nanoparticles between the two Pb electrodes , we have fabricated SSETs and investigated the transport properties of these devices . In the superconducting state , the conductance is suppressed by a combination of the single electron tunneling effect and the absence of density of states within the superconducting gap . In the suppression regime , the tunneling spectroscopy shows current features that arise from quasiparticle tunneling caused by singularity matching . At low temperature , the features can only be observed for odd charge states in SSETs . At high temperature , the odd -even parity effect is smeared out . Upon application of a magnetic field , the superconducting state is suppressed and single -electron tunneling behavior for normal metallic nanoparticles is recovered .
URI: http : / /hdl .handle .net /2152 /3747
Date: 2008-08-29

Citation

Electron transport in nanoparticle single-electron transistors. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /3747 .

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