Preparation of NbN by reactive magnetron sputtering using Ne and Kr inert diluents

Abstract

Previous studies of the preparation of NbN by reactive sputtering have employed Ar–N2 gas mixtures. We have shown that high‐Tc films (Tc=14.2 K) can be prepared on substrates held near room temperature by sputtering a Nb target in a dc s‐gun magnetron with that gas mix. This paper reports the results of an investigation of the properties of NbN films sputtered in the same system using alternative inert gas diluents, specifically Ne and Kr. The Tc of these films was found to depend systematically on the N2 partial pressure, total gas pressure, and dc cathode voltage; the maximum transition temperatures obtained using Ne–N2 and Kr–N2 mixtures were 12.8 and 12.7 K, respectively. When Tc is plotted versus ρ a rough general correlation is observed, though data for films sputtered in each inert gas tend to segregate. We conclude empirically that sputtering NbN in an Ar–N2 ambient gives the highest film quality and that using Ne or Kr in place of Ar offers no advantages.