EXAFS measurements on Nb3Ge thin films

The extended X-ray absorption fine structure (EXAFS) spectra has been measured for superconducting thin films of Nb3Ge prepared at variable deposition temperature by sputtering and electron beam coevaporation. As the deposition temperature is varied from 1050 K to 875 K, the film structure changes continuously from the A15 phase to a quasi-amorphous phase. This amorphous phase is characterized by a mean Ge-Nb distance of 2.66 A, as compared to the A15 distance, 2.87 A. The mean coordination of the Ge sites is reduced from 12 to 8 +- 2, and the mean square spread in Ge-Nb distance (thermal + spatial) has decreased by only 0.01 A2. (author)