Hysteretic Josephson junctions from high T/sub c/ superconducting thin films

Hysteretic superconductor-insulator-superconductor (SIS) and superconductor-normal metal-superconductor (SNS) Josephson junction devices have been fabricated from epitaxial thin-film structures. The SIS tunnel junctions were made of BKBO (Ba/sub 1-x/K/sub x/BiO/sub 3/) thin-film electrodes and a KNbO/sub 3/ barrier. Tunnel structures with gap voltages as high as 8 mV and switching voltages as high as 5 mV have been demonstrated. Nearly ideal SIS tunnel characteristics for high-temperature superconductive thin-film trilayer structures are reported. Zero bias currents are modulated by small magnetic fields and Shapiro steps are observed under RF-irradiation. SNS devices made from a YBCO (YBa/sub 2/Cu/sub 3/O/sub 7-y/) bottom thin-film electrode, a SrTiO/sub 3/ barrier, and a top BKBO film possessed McCumber parameters in excess of 100 and displayed I/sub c/R (critical-current resistance) products of up to 1 mV at 4.2 K.<>