Junction Using Ba1-xKxBiO3 Thin Films

We have fabricated a contact junction between an epitaxially grown YBa2Cu3O74 thin film and a polycrystalline Ba ?? xKxBiO3 thin film. This contact junction shows 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, 2Δ, is estimated to be 1.5 meV along the c-axis for YBa2Cu3O74 and 3 meV for Ba ?? xKxBiO3+ The 2Δ/kTc for the Ba ?? xKxBiO3 is about 3.5, which is equal to that derived from a boundary Josephson junction. These properties show that the contact boundary between YBa2Cu3O74 and Ba ?? xKxBiO3 works as the tunneling barrier.