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Title: High-resolution X-ray scattering studies of thin film superconductors and semiconductors
Author: Lin, Wen-Jih
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1998
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High-resolution x-ray scattering has attracted intensive attention for both fundamental research and industrial applications. Recently, the advance of synchrotron radiation sources has dramatically improved x-ray intensities, brightness and resolution, which has enhanced the ability of x-ray scattering studies. In spite of weak scattering cross-sections, high-brilliance x-ray sources have made the studies of surfaces and interfaces possible. In the last decade, many new x-ray techniques such as glancing-incidence-x-ray-reflectometry, crystal-truncation-rod analysis and reciprocal-space-mapping have been established and had great success in exploring the structure of various materials. This thesis starts with a review of high-resolution x-ray scattering which covers both the theoretical and the experimental backgrounds. Near perfect semiconducting thin films are examined to demonstrate the abilities of high-resolution x-ray scattering. Glancing incidence x-ray reflectometry was used to explore the interface morphology of a Si0.1Ge0.9 heterostructure grown with and without antimony acting as a surfactant. The results demonstrate that the film is smoother when grown with a sub-monolayer of the surfactant. Furthermore, due to the existence of the surfactant during growth, abnormal strong scattering was found from the long-range coherent conformal roughness. YBa2Cu3Ox thin film superconductors grown on various substrates from different growers were studied. Using high-resolution x-ray scattering techniques, the sample quality was measured using the position and the width of the Bragg reflections. By analysing the reciprocal space maps, the surface parallel lattice parameters were also determined. One of the best samples, the YBa2Cu3Ox grown on SrTiO3 by pulsed laser deposition was further studied. The results suggest that an ultra-high-quality crystal with thousands Ã…ngstrom vertical and microns horizontal correlation is occupied nearly 95% of volume. However, due to the interface roughness, the scattering from this crystal can only be observed at low angle Bragg reflections and, therefore, is often ignored. Because this type of film is the best single crystal high-Tc superconductor, it will be the doorway to understanding high-Tc superconductivity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available