Artificially structured superconductors

We have succeeded in making high T sub c films by three different techniques; sputtering from a stoichiometric YBa sub 2 Cu sub 3 O sub 7-x target, sputtering from Y and Ba sub 2 Cu sub 3 targets, and by co-evaporating BaF sub 2 while sputtering Y and Cu. The structure and composition of these films were characterized by a number of X-ray diffraction techniques. Physical properties measured included resistivity vs. temperature, electron tunneling, and infra-red optical reflectivity. Also during the past year, melt-processed Bi-Ca-Sr-Cu-O materials were fabricated and studied. A number of studies of low T sub c metallic superlattices were completed this past year. These included development of improved techniques for their deposition, as well as studies of their structure, elastic properties, interfacial structure and growth dynamics, superconductivity, and electron tunneling. We reported the successful fabrication of the first monolayer metallic superlattice, consisting of alternating single atomic monolayers of Mo and Ta. Unlike all previous metallic superlattices, this monolayer superlattice maintained long range structural coherence and good metallic behavior.