Nb-based SNS junctions with Al and TaO/sub x/ 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, have been fabricated obtaining devices with I/sub C/R/sub N//spl ap/0.5 mV. A second kind of junction has been fabricated using 10 nm thick non-stabilized TaO/sub x/ as a barrier, deposited by bias sputtering. For these devices, using the bias voltage as the main process parameter, I/sub C/R/sub N//spl ap/0.1 mV was obtained. Measurements of the electrical properties of the Nb/Al/Nb and the Nb/TaO/sub x//Nb junctions are reported.