Series arrays of NbSi barrier Josephson junctions for AC voltage standards

AC Josephson voltage standards are typically based on series arrays of overdamped Josephson junctions, which are presently realized using an Nb x Si 1-x barrier at PTB. The characteristic parameters of these SNS-like junctions can be tuned by the Nb content and the thickness of the barrier over a wide range for operation from 10 GHz to 70 GHz. Based on these junctions, we developed binary-divided 10 V arrays as well as pulse-driven arrays for 1 V output voltages.