Synchrotron-radiation photoemission studies of interface formation between metals and superconductors: Al and In on YBa/sub 2/Cu/sub 3/O/sub 6. 9/

The interfaces formed when the group-IIIA metals Al and In are deposited onto the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 6.9/ have been studied using high-resolution synchrotron-radiation photoelectron spectroscopy. Both Al and In deplete oxygen from the substrate to form their own oxides, which efficiently prevent further reaction between the substrate and the deposited metal. Subesequent deposition of metallic Al or In results in the formation of clusters. These heterogeneously reacted interfaces therefore exhibit superconducting, insulating, and metallic phases