Superconducting properties of In-Ge mixture films

We report on measurements of the perpendicular $H_{c\perp }$ and parallel $H_{c?}$ upper critical fields of superconducting In-Ge mixture films in a wide range of In concentrations. The resistivities of the samples varied from about 10 μΩ?, corresponding to high In concentration, up to about 1300 μΩ cm, corresponding to an In concentration close to the percolation threshold of the system. The critical temperatures of the samples in a zero external field have also been studied. For high metal concentrations the results have been analyzed and found to fit the predictions of the dirty limit for type-II superconductors. Near the threshold, however, where the normal-state resistivity goes to infinity, the critical fields saturate to a finite value. This result is in accordance with the prediction of percolation theory in the anomalous diffusion regime. As the threshold is approached the anisotropy ratio decreases to a constant value of 1.2 from its homogeneous type-II limit 1.69.