FABRICATION OF TUNNEL-JUNCTIONS WITH YBCO INSULATOR YBCO LAYERED STRUCTURE USING (013)-ORIENTED FILMS AS BASE LAYER

Tunnel junctions with a Y-Ba-Cu-O (YBCO)/SrTiO3 (STO)/YBCO layered str ucture were fabricated using (013)-oriented YBCO ((013)YBCO) as a base layer, for the first time. We observed obvious gap structures at arou nd 22 mV and around 10 mV, corresponding to twice the gap voltages par allel and perpendicular to CuO2 plane in the junctions, respectively. According to AFM images of the base (013)YBCO layer, the (013)YBCO sur face was not atomically flat. These results suggest that the dominant structures of the (013)YBCO surface were formed not by (013)-planes, b ut by both (010)- and (001)-planes.