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Title: Silicon single electron transistors in high magnetic fields for quantum computing
Author: Chapman, P.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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This report describes experimental work performed on highly phosphorous doped silicon single electron transistors (SET) both with and without a nearby isolated double-dot structure (IDD). Measurements are performed at milli-Kelvin temperatures and at 4K for magnetic fields from 0T to 15T. It is found for an SET that in some cases different single particle levels are being used depending on the direction of the voltage bias across the quantum dot. This is confirmed by the differing behaviour of the corresponding Coulomb peaks with magnetic field. Peak splitting with field is observed which is shown not to be an excited-state effect. A method is suggested involving charge-reorganisation on the dot in combination with a large variation of tunnel couplings of differing levels to the drain. A four-way splitting of a Coulomb peak is also observed. A spin-filling scheme is created using the behaviour of Coulomb peaks with magnetic field. Higher order spin transitions of ΔS=3/2 are observed. High polarisation is observed with as many as four electrons of the same spin being added consecutively. Strong hysterysis is noted between forwards and reverse-swept gate voltages using an IDD device. This hysterysis is absent with a bare SET device. Oscillations of current with field, identical over many Coulomb peaks are noted for an IDD device operating in the multi-electron transport regime. Much more variable oscillations with field oscillations with magnetic field are noted for an SET operating in the single-electron transport regime.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available