Low-Leakage Thin-Film Superconductor-Insulator-Normal Metal Tunnel-Junctions On Coevaporated Ba1-Xrbxbio3 And Rf-Sputtered Ba1-Xkxbio3

The oxide superconductors Ba1-xKxBiO3 and Ba1-xRbxBiO3 exhibit ideal BCS-like characteristics with T(c) approximately 30 K. We report the deposition of thin films with zero-resistance temperatures up to 25 K and transition widths less than 1 K by thermal coevaporation and rf sputtering. Thin-film S-I-N tunnel junctions fabricated by evaporating Ag or Au onto a native barrier exhibit low leakage over 1 mm2 junctions and near-ideal BCS-like behavior with a value of 2-DELTA(0)/k(B)T(co) = 3.5 +/- 0.2.