Study of the correlation between the structure and critical temperatureTc of sputtered Nb-Ge films

Nb-Ge layers with continuous change of chemical and phase composition were prepared by the d.c. sputtering method. The dependence of critical temperatureTc on phase composition, Ge-content, lattice imperfections and composition irregularities were studied. Films with highTc contain beside the A-15 Nb3Ge phase also the hexagonal and tetragonal modification of the Nb5Ge3 phase. Correlation betweenTc and Nb3Ge phase composition determined from the lattice parameter was found. In samples with highestTc the lattice parametera0=0·5135 nm corresponding to 22–23 at.% of germanium was determined.