Superconducting critical current of sputtered Nb-Ge films

The temperature dependence of the superconducting critical current density J_c(T) in zero applied field from 4.2 K to T_c has been measured for 15 films of Nb-Ge with varying composition, deposition conditions, and radiation damage. The results show (i) the enhanced superconductivity observed in stoichiometric Nb₃Ge as well as nonstoichiometric films is “bulk like” rather than filamentary, (ii) a simple correlation of the form which is reasonably independent of how the T_c has been achieved, and (iii) some additional evidence that the enhanced T_c of the films is not due to their chemical composition alone.