ELECTRICAL-PROPERTIES OF BOUNDARY BETWEEN YBA2CU3O7-DELTA AND BA1-XKXBIO3 THIN-FILMS

We have fabricated a contact between an epitaxially grown YBa2Cu3O7-δthin film and a polycrystalline Ba1-xKxBiO3thin film. This contact exhibits the typical I-V characteristics of quasi-particle tunneling which are observed for junctions consisting of electrodes having different superconducting energy gaps. From the I-V characteristics, the superconducting energy gap, 2 Δ, is estimated to be 1.5 meV along the c-axis for YBa2Cu3O7and 3 meV for Ba1-xKxBiO3. The 2 Δ/kTcfor the Ba1-xKxBiO3is about 3.5, which is equal to that derived from a boundary Josephson junction. These properties show that the contact boundary between YBa2Cu3O7-δand Ba1-xKxBiO3works as the tunneling barrier. © 1990 IOP Publishing Ltd.