The sputtering of A15 Nb₃Ge with controlled additions of oxygen

Abstract

A series of experiments designed to investigate the role of oxygen during the sputtering of the A15 superconductor Nb3Ge is reported. The overall trend found by other workers, of oxygen enhancing the Tc of ‘Nb3Ge’ in certain circumstances, is confirmed: however, two additional and associated effects are observed with our particular configuration of target and substrate. First, a tendency for the oxygen impurity to reduce the room temperature resistance ratio, and secondly, the appearance of two A 15 phases of slightly differing lattice parameter which are most discernible when oxygen impurity is present. A discussion of these effects and a detailed analysis of X-ray diffraction measurements is presented. It is concluded that oxygen, though beneficial for the formation of ‘Nb3Ge', is not necessarily the most critical parameter in the formation of stoichiometric Nb3Ge.