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

This paper reports on the properties of CrCu and CrCu-N thin films sputtered from a hot-pressed Cr40Cu60 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 degrees C and different substrate biases, U-n ranging from floating potential U-n 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-n and T-s = 300 degrees 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 degrees) reflections from (i) Cu(200) grains and (ii) an identified reflection at 2 theta = 52 degrees. (C) 1999 Elsevier Science S.A, All rights reserved.