Characteristics of Y-Ba-Cu-O/Nb and Bi-Sr-Ca-Cu-O/Nb tunnel-type Josephson junctions

The authors fabricated Y-Ba-Cu-O/Nb and Bi-Sr-Ca-Cu-O/Nb tunnel-type junctions and observed the DC and AC Josephson effects. Gold thin films were deposited for an interlayer to protect the reaction between the base electrode and the tunnel oxide before the tunnel barrier formation. In Y-Ba-Cu-O/Au/MgO/sub x//Nb junctions, superconducting current, hysteresis of current-voltage characteristics, and RF-induced voltage steps as high as 0.13 mV in the current-voltage characteristics were observed. Moreover, the superconducting current was modulated by the magnetic field. In Bi-Sr-Ca-Cu-O/Au/MgO/sub x//Nb junctions, superconducting current and RF-induced voltage steps as high as 0.15 mV were also observed.