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Some AB initio studies of positron annihilation in semiconductorsLi, Ming, 李銘 January 1998 (has links)
published_or_final_version / Physics / Doctoral / Doctor of Philosophy
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Probing defect and magnetic structures on the nanoscaleKallis, Alexis January 2010 (has links)
This thesis reports on experimental research on structural defects and magnetic species on the nanoscale. The latter project involved considerable development work on the production of a spin-polarised mono-energetic positron beam. The construction of the system is described through various trial steps with emphasis on the methods of maximum practical polarization of the positron beam and of electrons in the sample with the smallest possible loss of beam intensity. A new sodium-22 source capsule was purchased, having beryllium foil backing to minimise the depolarisation effects of backscattering, and the source-moderator spacing was increased. Different types of sample were tested, varying in atomic structure, purity, magnetic susceptibility, electronic structure, and electric conductivity - including iron of different purity and structure, mu metal and solid oxygen. After these tests measurements were taken on single crystal iron, and the results suggest that the positron response to magnetic structures is very small, and that prospects for depth profiling of dilute magnetic systems are not favourable at this time. A large number of other investigations have been performed on non-magnetic defect structures in various materials. Variable Energy Positron Annihilation Spectroscopy – here involving beam-based Doppler broadening – was applied to novel materials of relevance to photonic or electronic structures on the nanoscale. These included thin films of technological interest such as AlGaN and Ar plasma-treated TiO2: silicon and silicon-on-insulator samples implanted with He and Si ions to engineer vacancies: Si-rich SiO2 and SiN to form nanocrystals for photonic applications in which new findings on the evolution of the nanocrystals, and the role of the nanocrystal-oxide interface in optical emission, could be very useful in the technological development of such systems: and a study of the structural phase and nano-pore properties of water ice films grown from vapour on a cold copper surface. The variety of these experimental studies serves to underline the wide applicability of positron beam spectroscopy in research on defect and nanostructure structures. A list of papers published to date resulting from this work is given at the end of the thesis; a number of others are planned.
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Positron beam studies of the metal-GaAs (110) interface凌志聰, Ling, Chi-chung, Francis. January 1994 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
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Positron lifetime study of Zn-doped GaSb雷美琪, Lui, Mei-ki, Pattie. January 2001 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
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Defect characterization in binary aluminum-copper alloys by position annihilation spectroscopyLamport, Robert Anthony 05 1900 (has links)
No description available.
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The temperature dependence of positronium formation in high density polyethyleneNahid, Farzana. January 2008 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.
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A novel design of a variable energy positron lifetime beamChen, Dan, January 2007 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.
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Annihilation of positrons in solids [submitted] for the partial fulfillment of the degree of Master of Science in the Institute of Nuclear Science, National Tsing Hua University /Ma, Ing-Jiunn. Chen, Tuan-Wu. Chien, Ji-Peng. January 1900 (has links)
Thesis (M.S.)--National Tsing Hua University, (1960?). / Research done at the University of Michigan.
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Some AB initio studies of positron annihilation in semiconductors /Li, Ming, January 1998 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 103-105).
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Positron beam studies of the metal-GaAs (110) interface /Ling, Chi-chung, Francis. January 1994 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1994. / Includes bibliographical references (leaves 95-99).
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