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Title: The effects of strain on donor spin qubits in silicon
Author: Mansir, John
ISNI:       0000 0004 9352 550X
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2020
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Substitutional group V donors in silicon present a highly attractive spin qubit platform, o ering amongst the longest coherence times of any qubit implementation. Their use as qubits generally requires that they be incorporated into micro- or nano-electronic devices which are operated at cryogenic temperatures. These devices are typically fabricated from a variety of di erent materials which have coe cients of thermal expansion which can di er by as much as two orders of magnitude. As a result, strain in the silicon substrate is inescapable in such devices when cooled to their operation temperature. The current understanding of the e ects of strain on donor spins is based on the valley repopulation model of Wilson & Feher [1]. In this work, we rst present the discovery of a novel, linear mechanism coupling strain to the strength of the donor hyper ne interaction, which overturns this conventional wisdom, and opens up new opportunities for local tuning of donor spins as well as coupling to mechanical resonators. Next, we explore the physics of the donor-bound exciton, a four-particle excited state which presents an as yet unrealized opportunity for hybrid optical/electrical single-donor spin readout. We develop a theoretical model which predicts that strain also has signi cant e ects on the physics of the donor bound exciton transition, and as such we present an experimental investigation of these e ects. We then develop a nite-element simulation technique which allows strain distributions to be predicted inside nanoelectronic devices, and combine these simulations with the theoretical strain model to inform the design of the geometry and optimal donor placement for devices which intend to use the donor-bound exciton transition as a readout mechanism. Finally, the results of experimental attempts to measure the signature of a single donor-bound exciton in a variety of nanoelectronic devices are presented.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available