Superconductivity defects and stoichiometry in A15 materials

We have fabricated thin films of Nb3Ge, Nb3Sn, V3Si and V3Ge and investigated their superconducting and structural properties. In the case of the Nb compounds the dependence of Tc, resistance ratio and phase on stoichiometry have been determined. Defects have also been introduced into these films, in a controlled fashion, by irradiation with 1.9 MeV⁴He particles, and the structural and superconducting properties measured. The results indicate a universality of behavior in these materials and suggest that stoichiometry is not the most crucial parameter in affecting Tc.