Nb-based SNS junctions with Al and TaOx barriers for a programmable Josephson voltage standard

We report results achieved in the fabrication of two different Nb-based SNS devices which can be used for the development of a programmable Josephson voltage standard. Junctions with an Al metal barrier, 5 to 100 nm thick, ha ve been fabricated obtaining devices with ICRN approximate to 0.5 mV. A sec ond kind of junctions has been fabricated using 100 nm thick non-stabilized TaOx as a barrier, deposited by bias sputtering. For these devices, using the bias voltage as the main process parameter, ICRN approximate to 0.1 mV was obtained. Measurements of the electrical properties of the Nb/Al/Nb and the Nb/TaOx/Nb junctions are reported.