Superconductivity and localization in thin polycrystalline tungsten-germanium films

We report magnetoresistance measurements on a high-resistivity (≊200 μΩ cm) crystalline material that becomes superconducting. Our samples are thin polycrystalline ${\mathrm{W}}_{100\mathrm{-}\mathit{x}}$ ${\mathrm{Ge}}_{\mathit{x}}$ (x=16–18) films, measured above the superconducting transition temperature. This is an opportunity to test the predictions for electron-phonon scattering in the presence of strong elastic scattering. The films are deposited using a low-temperature chemical-vapor-deposition process and show the crystalline β-W structure (A15) with a ${\mathit{T}}_{\mathit{c}}$ of around 3 K and ${\mathit{H}}_{\mathit{c}2}$ near 8 T. Contributions from both superconducting fluctuations and weak localization to the magnetoresistance are discussed and the inelastic-scattering rate is found to be determined by electron-phonon scattering.