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Title: SR studies in semiconductor, semi-metal and powder systems and the application of a pulsed low energy muon beam line
Author: Donnelly, P. A.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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The work contained in this thesis regards both surface related techniques, and the use of the muon as a hydrogen analogue in the investigation of fast charge-exchange cycles. Using conventional muon beams, muonium interactions with the surface of a fine silica powder are studied, via the addition of condensed rare gases (He, Ar, Kr, Xe) in sub-monolayer converges. We prove for the first time that at least 60% of the muonium yield is formed at the surface of the powder grains, and discount the possibility that bulk formed muonium is dissociated at the surface by ionised gas atoms. An additional mechanism for muonium formation, based on atomic recoil, is also proposed. Muon spin-rotation measurements on silicon show the onset of a substantial paramagnetic shift from the muon Larmor frequency. The inferred fraction of the time spent as neutral paramagnetic muonium is close to unity above 600 K, so the capture rate of conduction electrons greatly exceeds the effective ionisation rate. Configuration-coordinate models for the interplay between site and charge state are described and developed. A number of non-magnetic semimetals and metals are found to exhibit significant muon spin relaxation, which suggests a form of Korringa relaxation, also linked to conduction electron encounter at an interstitial site. The relationship between relaxation rate and muon Knight shift is investigated; we look briefly at the nature of defect screening; and consider the similarities with electronic activity seen in semiconductors at high temperatures.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available