High quality Nb-AlO/sub x/-Nb junctions for microwave receivers and SFQ logic device

The specific capacitance of high-quality (V/sub m/>50 mV) Nb-AlO/sub x/-Nb tunnel junctions is determined by the following methods: the measurement of zero field step resonances in specially prepared long Josephson junctions, and the definition of the resonant voltages in two-junction interferometers based on Nb-AlO/sub x/-Nb junctions. The results obtained by these methods were compared with each other and with the figures calculated from the measurements of tunnel barrier parameters. The application of the procedure for the fabrication of single flux quantum (SFQ) logic devices is discussed.