V3Si-SiOx-Mo3Re2superconducting tunnel junctions

The possibility of obtaining sandwich-type Josephson junctions that can be operated at temperatures higher than 10 K is examined. A high-Tcsuperconductor which can be deposited at substrate temperatures below room temperature is found, and the tunnel junctions are fabricated, therewith. Tunnel junctions are made by using the high-Tcsuperconductors V3Si and Mo3Re2for the base electrode and counterelectrode, respectively. These films are prepared by a co-evaporation technique. Oxide-barrier formation is performed by oxidizing a Si thin film 2 to 3 nm thick which is deposited before exposing the V3Si film surface to air. The superconducting onset temperature of the V3Si thin film is 16 K. The Mo-Re thin film has a metastable A-15 type phase in the Re concentration range of 25 to 50 at.%. The Tcof the Mo3Re2thin films deposited on the room temperature substrate is 10-11 K. However, the Tcvalue decreases as the substrate temperature is lowered with a background gas pressure of about 10^-4Pa. In fabricating the V3Si-SiOx-Mo3Re2junctions, the Mo3Re2thin film is deposited with the substrate at lower than room temperature. Superconducting characteristics are observed in the current-voltage curve of the junction.