INTERACTIONS AT THE SUPERCONDUCTOR-METAL INTERFACE

The interfacial chemistry between a superconducting oxide (Y(1)Ba(2)Cu (3)O7(-x)) and metallic adsorbates has been studied with the idea of u nderstanding what processing steps can modify the interface. X-ray Pho toelectron Spectroscopy has been used to study the growth of Ag on thi s oxide during the initial stages of bond formation. These results hav e been compared to that of a more reactive metal such as Ni. It is see n that even though Ag grows as metallic atom and Ni grows as Ni-O at t he first interfacial monolayer, the surface reduction of Cu is identic al in the two cases. This indicates that in the absence of a thermodyn amic redox reaction, there is no direct correlation between the oxygen affinity of the adsorbate and the extent of chemical reduction seen i n surface copper ions. This apparent reduction, which may therefore ar ise from adatom-induced restructuring, can be prevented if the superco nductor is exposed to bromine gas prior to silver deposition. These re sults have been analyzed in light of the available literature in this area. The possible impact of this finding on Ag-superconductor composi te processing has been discussed.