Localization and interaction effects in ultrathin amorphous superconducting films

Abstract

Ultrathin superconducting films of amorphous Mo-Ge were made that remain homogeneous down to \ensuremath{\sim}20 \AA{}. The expected localization behavior was observed in their resistivity-versus-temperature and sheet resistance (${R}_{\ensuremath{\square}}$) data. A systematic reduction of the transition temperature with increasing ${R}_{\ensuremath{\square}}$ was observed for several compositions, consistent with recent theories of localization and Coulomb interaction effects on superconductivity. Critical-field data provide further tests of these theories.