Bridge Type Josephson Junctions in MO-CVD Thin Films

Using Y 1 Ba 2 Cu 3 O 7- x thin films, bridge type Josephson junctions are fabricated. Thin films of Y 1 Ba 2 Cu 3 O 7- x on (100) MgO substrates are deposited by the MO-CVD method. These films exhibit zero resistance at 86 K, and a critical current density of 10 4 to 10 5 A/cm 2 at 77 K. The effect of radio frequency irradiations to the bridge are investigated. Sharp microwave-induced steps are observed up to 800 µV at 77 K for X band irradiation. Clear Shapiro steps are also observed at the millimeter (101 GHz) and submillimeter frequency (303 GHz). The results demonstrate that the thin film bridges made by MO-CVD show an ideal ac Josephson effect.