Tunneling and interface structure of oxidized metal barriers on A15 superconductors

Al5-based tunnel junctions have been prepared with barriers of oxidized Al; Si, and Y. Properties of the superconductor/barrier interface which are crucial for low-leakage junctions were established by correlating XPS spectra of oxidized bilayers and RHEED patterns of the surface of each layer with tunneling characteristics. Comparisons were made between oxidized Al barrier properties for Nb and Nb3Sn base electrodes. Some differences between evaporated and dc magnetron sputtered barriers have emerged.