FABRICATION OF YBACUO NONSUPERCONDUCTIVE-YBACUO/YBACUO COPLANAR JOSEPHSON-JUNCTION BY FOCUSED ION-BEAM

摘要

Thin film of YBa(2)Cu3O(7-delta) grown on the MgO substrate damaged by a focused ion beam loses superconductivity due to an abnormal growth. We have fabricated a YBa2Cu3O7-delta co-planar Josephson junction whose coupling region is a nonsuperconductive YBa2Cu3O7-delta grown on an MgO substrate damaged locally by a scan of a focused ion beam. The I-V characteristic of the junction behaves like a flux how type. At temperatures from 4.2K to 60K, Shapiro steps were observed for the junctions in which the length of the coupling region was from 0.2 mu m to 1 mu m. The highest IcRn product of the junction was 5.0mV. The critical current density decreased exponentially with the junction length. It is considered that nonsuperconductive YBa2CU3O7-delta grown on the damaged substrate works as a normal layer in an S-N-S junction. Also the junction responded to the magnetic field and behaved like asymmetric de-SQUID.