Microstructure, dimensionality, and depression of the transition temperature in disordered superconducting films

Composite In/${\mathrm{InO}}_{\mathrm{x}}$ films are reproducibly fabricated with two classes of microstructure, islanded at low oxide content and amorphous-composite at high oxide content. The islanded films, near the percolation threshold, exhibit a two-dimensional depression of the mean-field transition temperature proportional to normal-state sheet resistance. The corresponding behavior in the amorphous composite films with similar resistivities is three-dimensional with a quadratic dependence on normal-state resistivity. Consistency with respective theory for each case is discussed.