BA1-XKXBIO3 THIN-FILM JOSEPHSON TUNNEL-JUNCTIONS

We have fabricated sandwich-type Josephson tunnel junction devices fro m Ba1-xKxBiO3 electrodes and KNbO3 insulating barriers. Near ideal sup erconductor-insulator-superconductor tunnel junction pp structure was seen in high resistance devices at 4.2 K. Lower resistance devices wit h similar gap structure but much higher subgap leakage were hysteretic with switching voltages up to 5 mV. Hysteresis and well-defined gap s tructure persisted past 12 K. Magnetic field modulation of the zero-bi as pair current showed Fraunhofer-like behavior with almost complete q uenching at the nodes.