CHARACTERIZATION OF YBA2CU3O7-X COPLANAR JOSEPHSON-JUNCTIONS USING FOCUSED ION-BEAM

YBa2Cu3O7-delta co-planar Josephson junctions by Focused Ion Beam were characterized by changing the thickness of YBa2Cu3O7-delta films. The junctions had the thickness dependence of the characteristics. The ch aracteristics were dominantly divided into two types. One had the I-V curve of a Aux-flow junction and a weak magnetic response. The other h ad the I - V curve of RSJ, the IcRn product from 0.1 mV to 0.5 mV at 4 .2 K, and a good magnetic response. The critical current density of th e junctions increased exponentially with increasing film thickness. Fr om the observation of the junction surface, the junction length was de creased with increasing film thickness by the horizontal growth of the normally grown YBaCuO. In the thicker film (above 240 nm), the micros horts of the normally grown YBaCuO on the abnormally grown YBaCuO area were observed. It is considered that the main part of Josephson curre nt for the junctions changes from the abnormally grown YBaCuO to micro shorts when increased with the film thickness.