Tunnel junctions using oxide superconducting thin films epitaxially grown on SrTiO3.

Normal-metal/insulator/superconductor (NIS) junctions were fabricated using thin films of YBa2Cu3O7-x (YBCO) or ErBa2Cu3O7-x. These were epitaxially grown on single-crystal SrTiO3 by the activated reactive evaporation method. For some NIS junctions prepared on SrTiO3 (110) substrates, we observed multipeaks in the differential conductance versus voltage curve. NIS junctions using single-crystal YBCO films on SrTiO3 (100) showed a set of peaks, from which we obtained a gap parameter of 11.5±1.5 meV at 4.4 K and a coupling constant of 3.2±0.4. [ABSTRACT FROM AUTHOR]