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Title:Growth, fabrication, and measurement of superconducting barium(1-x) potassium bismuth oxygen(3) thin films and devices
Author(s):Schweinfurth, Ralph Alan
Doctoral Committee Chair(s):Van Harlingen, Dale J.
Department / Program:Physics
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Physics, Condensed Matter
Engineering, Materials Science
Abstract:This thesis discusses growth, fabrication and measurement of $\rm Ba\sb{1-x}K\sb{x}BiO\sb3$ (BKBO) superconducting thin films and thin film devices. Interest in BKBO has been concerned with both fundamental questions concerning its mechanism of superconductivity and potential applications in superconductor devices. $\rm Ba\sb{1-x}K\sb{x}BiO\sb3$ is a superconducting compound at a small range of potassium concentration, with the highest transition temperature being about $32\sp\circ\rm K$ for 0.35 $<$ x $<$ 0.4 The in-situ growth of high quality superconducting thin films is described, using pulsed laser deposition. Film quality was analyzed with RBS, XRD, and SEM as well as transport. Fabrication of transport, microwave, and tunneling structures and devices is described, including dry etching techniques (ion milling and RIBM) as well as annealing and processing effects. Transport measurements yield $\rm T\sb{c0}$ = 25-29$\sp\circ\rm K,$ $\rm J\sb{c}$ $\ge$ 1 $\rm MA/cm\sp2$ $(4\sp\circ\rm K),$ and $\rm R\sb{s}$ $\approx$ 1 $\rm m\Omega$ (at $4\sp\circ\rm K$ and 10GHz) for the best films. Dissipation in fields up to 5 Tesla suggests that the superconducting coherence length $\xi\approx 38\rm\A$ and upper critical field $\rm H\sb{c2}(0)\approx$ 22T. Tunneling studies were also made using a BKBO electrode, a native oxide barrier, and the following counterelectrodes: Ag, Pb, Nb, and BKBO. Results were consistent with classical tunneling of a weak to moderately coupled superconductor where $\Delta$ = 4.5 meV and $2\Delta\rm /k\sb{B}T\sb{c}$ = 3.8. Prospects for practical BKBO superconducting devices are discussed.
Issue Date:1994
Rights Information:Copyright 1994 Schweinfurth, Ralph Alan
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9503312
OCLC Identifier:(UMI)AAI9503312

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