Fabrication and Josephson properties of Nb3Ge

Sputtering techniques have been used to fabricate Nb3Ge films on amorphous substrates which exhibit superconductivity up to about 21 K. Of the many sputtering parameters that can be varied, the most important appear to be target geometry and composition and substrate temperature. Initial results of analyzing the composition indicate that a Ge-rich phase nucleates during the initial stages of the deposition. Josephson microbridges have been fabricated from these films and microwave-induced steps in the I-V curves have been observed in micron-sized bridges. An interpretation of the criticality of the bridge size in terms of a vortex state is given.