Tunneling and surface properties of oxidized metal overlayers on Nb.

The present status of Bell Labs tunneling and surface physics work on Oxidized Metal Overlayers (OMO) is summarized and placed in perspective with other work in the filed of superconducting tunnel junctions. In this paper we emphasize features of interest to tunneling applications; the related topic of OMO use in tunneling spectroscopy of transition metals is referenced but not discussed. The central result of this work consists of the demonstration that using thin OMO's (M=Al), all-refractory Josephson tunnel junctions with nearly ideal BCS electrical characteristics can be fabricated.