INTERFACE BETWEEN GOLD AND SUPERCONDUCTING YBA2CU3O7-X

Gold (Au) and silver (Ag) are known to be important contact metals on YBa2Cu3O7-x (YBCO). Both metals have been used as additives in fabrica ting tapes of YBCO and Bi2Sr2CaCu2O8 (BSCCO) materials, and have favor able results in improving not only the flexibility but also the weight ed critical currents of the resulting composites. Previous results on superconductor/normal metal/superconductor junctions made using YBCO/A u/YBCO and YBCO/Au/Nb demonstrated that a supercurrent can be induced in the normal metal layers through the proximity effect. Our transmiss ion electron microscopy study of the Au/YBCO interfaces shows a well-b onded interface with no extraneous phases present. Lattice fringes of the (001) plane in YBCO terminated at the interface abruptly. This obs ervation supports previous results of contact resistance of x-ray phot oelectron spectroscopy (XPS). Both (001) integral steps and multiples of 1/3 (001) steps were observed at the Au/YBCO interface. When the to p gold layer was absent locally, surface degradation was observed as t he (001) lattice fringes stopped short from the surface by 10 nm. Our results support that Au is a desirable contact metal and a dependable surface passivation material for YBCO.