ENHANCEMENT OF SUPERCONDUCTIVITY AND OBSERVATION OF ANTILOCALIZATION IN THIN METAL-FILMS BY SUPPRESSION OF ELECTRON-INTERACTION EFFECTS

We have studied superconductivity and temperature dependence of resistance in thin Ta films covered by a layer of anodic oxide. It was shown that deposition of a thick gold film on top of the oxide dielectric layer enhances the superconductivity of the thin film and changes the sign of the temperature dependence of resistance through changing the dominant quantum correction from electron-electron interaction to antilocalization. The results demonstrate that the proximity of a thick metal film, even without any electrical contact to the thin film, reduces the Coulomb interaction between conduction electrons in the thin film, thereby turning off most of the interaction quantum correction to conductivity. Consequently, the only quantum correction remaining is weak localization. This does not affect the superconductivity and has the antilocalization sign in Ta, as is expected for a metal of large atomic number. © 1994 The American Physical Society.