Nanocrystalline and nanocomposite CrCu and CrCu–N films prepared by magnetron sputtering

Abstract

This paper reports on the properties of CrCu and CrCu–N thin films sputtered from a hot-pressed Cr 40 Cu 60 target in Ar and Ar+N 2 at the same total pressure of 0.5 Pa, respectively. Films were sputtered at different substrate temperatures, T s , ranging from room temperature (RT) to 650°C and different substrate biases, U s , ranging from floating potential U fl to −700 V. It was found that the Cu content in the films decreases with increasing negative bias U s . The CrCu–N film deposited at U s = U fl and T s =300°C contains 43 at.% Cu, 30 at.% Cr, 27 at.% N and exhibits a relatively low microhardness HV=17 GPa. On the contrary, the CrCu–N film sputtered at the same T s but at U s =−500 V and substrate ion current density i s =1.6 mA/cm 2 contains only 1 at.% Cu, 48 at.% Cr and 51 at.% N and exhibits a high microhardness HV=35 GPa. The content of Cu in the CrCu–N film also strongly affects its structure. The films containing less than 8 at.% Cu are composed of relatively large (50–90 nm) CrN(111) grains; no crystalline Cu phase is observed. On the contrary, films containing more than 25 at.% Cu exhibit a disordered structure with very small grains , 5 nm in size only. These films are characterized by two small and broad (about 5°) reflections from (i) Cu(200) grains and (ii) an identified reflection at 2 θ =52°.