Josephson Effects at 77 K in Grain Boundary Bridge Made of Thick Films

Using the screen printing method, YBaCuO high T c superconducting films were fabricated. The thickness of the films was ≃30 µm and maximum grain size was ≃70 µm. T czero=90.7 K and J c=20 A/cm2 at 77 K were obtained. With a razor edge, the films were cut and formed to grain boundary bridges having a few grain boundaries in the bridge region. The devices showed clear Shapiro steps and SQUID patterns at 77 K.