Josephson Tunnel Junctions with Nb, NbN Double-Layered Electrodes

Abstract

Josephson tunnel junctions with double-layered base and counter electrodes composed of Nb and NbN have been developed. The tunneling characteristics of the junctions and the effective penetration depth of the double-layered electrodes have been measured as a function of the thicknesses of the NbN and Nb films. It has been found that, by using the double-layered electrodes with a 100 nm-thick-NbN film and a 50 nm-thick-Nb film, the effective penetration depth can be sufficiently decreased without losing the large gap voltage of 4.4 mV and the small subgap conductance of 14 mV.