Properties of RF sputtered Nb3Ga superconducting films

Niobium-gallium films with a composition range of 8 at. % to 35 at. % Ga have been prepared using RF sputtering techniques. A variable composition sputtering target, fabricated from Nb and NbGa3powders, was used to vary the lengthwise composition as deposited on polished Al2O3substrates. The effects of deposition temperature, subsequent heat treatment, and background impurity pressure during sputtering, were studied in relation to crystalline structure, film composition, resistive Tc, and resistivity ratio. Maximum Tcvalues occur in the 30 at. % Ga region of the film when gaseous impurity levels are high, and after the films are given a 700°C vacuum anneal.