Dependence of Critical Current Density on Oxygen Exposure in Nb-AlOx-Nb Tunnel Junctions

We demonstrate that a large fraction of the available data relating the critical current density J, of superconducting Nb-A1Ox-Nb tunnel junctions to oxidation parameters can be accounted for by a single, nearly universal dependence. For fixed oxidation temperature, J, does not depend independently on oxygen partial pressure and oxidation time, but only on their product. There are two distinct regimes in this dependence, corresponding to high and low Jc. © 1995 IEEE