The dependence of $T_c$ upon 2-MeV ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ damage has been investigated in ${\mathrm{Nb}}_3$Ge, ${\mathrm{Nb}}_3$Sn, ${\mathrm{V}}_3$Si, and ${\mathrm{V}}_3$Ge superconducting thin films. Similar $T_c$ versus dose plots are observed for all materials. At high doses $T_c$ saturates at 3.5 K (${\mathrm{Nb}}_3$Ge), 2.95 K (${\mathrm{Nb}}_3$Sn), 2.2 K (${\mathrm{V}}_3$Si), and 1.0 K (${\mathrm{V}}_3$Ge). Optimum values of $T_c$ are obtained for Nb:Ge and Nb:Sn ratios throughout the compositional range of 2.6:1-3:1 in 95% single-phase $A15\mathrm{}$ films.

• Received 10 June 1976

DOI:https://doi.org/10.1103/PhysRevLett.37.1308