Nb/Al-oxide/Nb and NbN/MgO/NbN Tunnel Junctions in Large Series Arrays for Voltage Standards

Abstract

Series arrays of 1440 Josephson tunnel junctions were fabricated out of Nb/AN-oxide/Nb- and Nb/NbN/MgO/NbN/Nb-sandwiches The arrays provide microwave-induced constant voltage steps of at least one volt. The good stability of hard superconductor tunnel junctions against room temperature storage and thermal cyling suggests that these arrays might be very useful for the constructions of practical lasting Josephson voltage standards of high precision.