Growth, Fabrication, and Measurement of Superconducting BARIUM(1-X) Potassium Bismuth OXYGEN(3) Thin Films and Devices

This thesis discusses growth, fabrication and measurement of rm Ba_{1-x}K _{x}BiO_3 (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_ {1-x}K_{x}BiO_3 is a superconducting compound at a small range of potassium concentration, with the highest transition temperature being about 32^circrm 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_{c0} = 25-29^circrm K, rm J_{c} >= 1 rm MA/cm^2 (4^circrm K), and rm R_{s} ~ 1 rm mOmega (at 4 ^circrm K and 10GHz) for the best films. Dissipation in fields up to 5 Tesla suggests that the superconducting coherence length xi ~ 38A and upper critical field rm H_{c2}(0)~ 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 2Deltarm /k_{B }T_{c} = 3.8. Prospects for practical BKBO superconducting devices are discussed.