INFLUENCE OF MICROSTRUCTURE IN THE LOW-TEMPERATURE CRITICAL CURRENTS OF YBA2CU3O7-DELTA THIN-FILMS

Epitaxial YBa2Cu3O7-delta films nucleate in c-axis oriented single-cry stalline islands. The surface of the single-crystalline SrTiO3 substra tes exhibit steps of one third of the YBa2Cu3O7-delta c-axis. These st eps generate a mismatch in the island boundaries between the CuO2 supe rconducting blocks. We show that these defect regions are strong candi dates for being the pinning centers responsible for the large critical currents observed in Laser Ablated and Sputtered thin films.