Author: Engang Fu

Publisher: Open Dissertation Press

Published: 2017-01-27

Total Pages:

ISBN-13: 9781374667174

This dissertation, "Study of Epitaxial Thin Films of YBa2Cu3O7-[delta] on Silicon With Different Buffer Layers" by Engang, Fu, 付恩剛, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled STUDY OF EPITAXIAL THIN FILMS OF YBa Cu O ON 2 3 7-δ SILICON WITH DIFFERENT BUFFER LAYERS submitted by Fu Engang for the degree of Master of Philosophy at The University of Hong Kong in August 2005 Silicon is the most widely used semiconductor in the microelectronic industry. Highly epitaxial thin films of YBa Cu O (YBCO) grown on Si wafers are of 2 3 7-δ special interest for development of superconductor/semiconductor hybrid microelectronic devices and circuits. However, severe interaction between Si and YBCO layer, large mismatch in their lattice constant, and strain due to different thermal expansion often degrade the crystallinity and superconductivity of the grown YBCO layers. In this study, yttria-stabilized zirconia (YSZ) and Eu CuO (ECO) 2 4 were introduced as double buffer layers to improve the growth and properties of the YBCO thin films grown on silicon. Preparation and characterization of epitaxial YBCO/ECO/YSZ/Si multilayer structures were studied. YBCO thin films and the double buffer layers of ECO/YSZ were deposited on the silicon (100) substrate by the pulsed laser deposition (PLD) method. Firstly, the YSZ thin layer was grown epitaxially on silicon (100) substrate to separate YBCO from the Si substrate. Effects of substrate temperature and operating gas pressure on the structure and surface roughness of YSZ thin film were examined and the optimum deposition parameters were determined based on experimental results and comprehensive analysis. X-Ray diffraction (XRD) patterns and rocking curve revealed an epitaxial growth with a perfect c-axis orientation. The YSZ thin films grown on silicon substrate have smooth surface, providing a base on which ECO and YBCO thin film can be grown epitaxially. To further improve the quality of YBCO films, an additional layer of ECO with very stable 214-T' crystal structure was inserted between YBCO and YSZ/Si. The influence of substrate temperature and oxygen gas pressure on the properties of ECO thin films grown on YSZ/Si were experimentally analyzed and the growth conditions were optimized. Finally, the epitaxial YBCO thin films were grown on silicon substrate with double buffer layers of ECO/YSZ. The influences of substrate temperature, oxygen gas pressure and different buffer layers on the properties of YBCO thin films were studied. It was found that the crystal structure, surface roughness and superconductivity of YBCO films could be significantly improved by adding such a double buffer of ECO/YSZ. The quality of the YBCO thin films has been significantly enhanced when compared with that grown on Si with a single YSZ buffer layer and with double buffer layers of Nd CuO (NCO)/YSZ. Such highly 2 4 epitaxial thin films of YBCO grown on silicon should be of great interest for various applications including high-frequency elements, millimeter-wave receivers, and superconducting quantum interference devices. DOI: 10.5353/th_b3637488 Subjects: Thin films Silicon Epitaxy