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Browsing by Author "Law, Ka Ming"

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    Demonstration of nearly pinhole-free epitaxial aluminum thin films by sputter beam epitaxy
    (Nature Portfolio, 2020) Law, Ka Ming; Budhathoki, Sujan; Ranjit, Smriti; Martin, Franziska; Thind, Arashdeep S.; Mishra, Rohan; Hauser, Adam J.; University of Alabama Tuscaloosa; Washington University (WUSTL)
    Superconducting resonators with high quality factors have been fabricated from aluminum films, suggesting potential applications in quantum computing. Improvement of thin film crystal quality and removal of void and pinhole defects will improve quality factor and functional yield. Epitaxial aluminum films with superb crystallinity, high surface smoothness, and interface sharpness were successfully grown on the c-plane of sapphire using sputter beam epitaxy. This study assesses the effects of varying substrate preparation conditions and growth and prebake temperatures on crystallinity and smoothness. X-ray diffraction and reflectivity measurements yield extensive Laue oscillations and Kiessig thickness fringes for films grown at 200 degrees C under 15 mTorr Ar, indicating excellent crystallinity and surface smoothness; moreover, an additional substrate preparation procedure which involves (1) a modified substrate cleaning procedure and (2) prebake at 700 degrees C in 20 mTorr O-2 is shown by atomic force microscopy to yield nearly pinhole-free film growth while maintaining epitaxy and high crystal quality. The modified cleaning procedure is environmentally friendly and eliminates the acid etch steps common to conventional sapphire preparation, suggesting potential industrial application both on standard epitaxial and patterned surface sapphire substrates.
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    Paving a Road for Novel Material Research: Complementing Sputter Beam Epitaxy with Practicality-Oriented Ab-Initio Method
    (University of Alabama Libraries, 2023) Law, Ka Ming; Hauser, Adam
    Breakthroughs in material science demand high-crystallinity, structurally or atomically complex, new materials. The development of new materials in thin film form provides key advantages for technological integration, due to the prominence of thin film applications such as coatings and heterostructure devices. However, not all thin-film fabrication techniques are ideal for producing thin films of complex materials with high phase purity and atomic ordering, particularly when the epitaxy between substrate and film are not closely related. In this dissertation, I shall discuss the principles and techniques for novel material research, by presenting three studies of mine.