Structural, Chemical and Electronic Properties of Superconducting Thin Films andJunctions

摘要

Ba(1-x)K(x)BiO3 (BKBO) has a transition temperature, T(sub c), of 34 K and isunique among the high-temperature oxide superconductors because it is isotropic. It has been little studied and it is desirable to understand its behavior from the perspectives of both potential electronic applications and fundamental understanding of superconductivity. This study has involved a determination of the structural, electronic, and chemical properties of BKBO films and junctions deposited by rf magnetron sputtering. It was found that films with the highest T(sub c) and lowest rocking curve widths were consistently grown on SrTiO3. This material was therefore used as a buffer layer for growing high-quality BKBO films on the more practical substrates LaAlO3 and NdGaO3. SrTiO3 was also used as a barrier to fabricate BKBO/SrTiO3/BKBO SIS junctions for the first time. These junctions exhibited tunneling behavior. Modelling based on electrical measurements and electron diffraction observations of surface structure indicated island-type growth of the barrier material. The thickness variation in the tunnel barrier as a result of island formation limits the practical potential of such junctions in most applications where tunneling current uniformity and junction reproducibility are required. jg.