INFLUENCE OF SRTIO3 BICRYSTAL MICROSTRUCTURAL DEFECTS ON YBA2CU3O7 GRAIN-BOUNDARY JOSEPHSON-JUNCTIONS

Using near-field scanning optical microscopy (NSOM), we observe an inh omogeneous distribution of submicron-sized structural defects at the f usion boundary of polished SrTiO3 bicrystal substrates. Both NSOM and scanning force microscopy show that these substrate defects cause the grain boundary of a YBa2Cu3O7 thin film grown on the bicrystal to wand er up to a micron in the film. These structural defects an shown to co rrelate qualitatively with the electrical characteristics of grain-bou ndary Josephson junctions patterned on the YBa2Cu3O7 film. (C) 1997 Am erican Institute of Physics.