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Title: X-ray studies of defects in diamond and gallium arsenide
Author: Clackson, Stephen Gregory
Awarding Body: University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1989
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Diamonds from mines in South Africa, and the Argyle Mine in Western Australia, have been compared using synchrotron transmission Laue photography (Laue topography), and the Argyle stones were found to be more variable in quality. By measuring the asterism of the Laue spots, quantitative estimates of lattice distortion have been made. The various types of crystal distortion, and their effects on Laue patterns, have been considered, and it has been determined that distortion in the Argyle diamonds primarily takes the form of mosaic structure. A modification of the technique of x-ray spike topography, where parts of the specimen were obscured by a tantalum screen, has been used to estimate platelet dimensions at different positions in type 1a diamonds. Direct measurements of the platelets in some of the samples have been made from transmission electron micrographs, and show that the method is reasonably reliable for platelets below about 400 A in diameter. In the range 1361.3 to 1371.3 wavenumbers, a correlation has been confirmed between 'platelet peak' position in the infrared spectrum and platelet size, in the sense of smaller wavenumbers being associated with larger platelets. Topographs of gallium arsenide wafers, used for device fabrication, have been taken. A dislocation lineage has been studied in a (100) wafer with field effect transistor arrays fabricated onto it. It has been found to cause a drop of approximately 40 mV in the pinch-off voltage of transistors it touches. The feature has been shown to have an associated Burgers vector of the 211-type, and to be accompanied by a lattice tilt in the wafer of nearly 30". Previous work in each area of investigation is reviewed, and brief introductions on diamond and gallium arsenide given, together with introductions to the techniques of topography, using both characteristic x-rays and synchrotron radiation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Condensed Matter Physics