High-resistance SNS sandwich-type Josephson junctions

We have investigated the behavior of SNS and SIS junctions with barriers in the vicinity of the Metal-Insulator (M/I) transition. We use Nb for the superconductor and amorphous-(Nb-Si) for the barrier. All junctions were made by means of electron-beam evaporation on Al2O3substrates. The junction areas were defined by the Selective Niobium Anodization Process (SNAP). We have made junctions down to 8 × 8 μm²and barrier thicknesses in range from 250 Å to 600 Å. The composition of the barrier was varied from 5 % Nb to 15 % Nb. Working on the metallic side of the M/I transition we observe μ-bridge-like I-V characteristics with RNA m²and IcRN V.