[en] The interdiffusion behavior of chromium oxide films rf-sputtered in O₂ ambient onto substrates of bulk Cu as well as approx.100 nm thin films of Cu was studied using Auger electron and ion scattering spectrometries. Composition depth profiling was carried out for films deposited on substrates which were untreated, thermally oxidized, and plasma oxidized and had other surface pretreatments. Interdiffusion of Cr₂O₃ films with bulk and thin film Cu substrates is observed even in the unannealed samples and increases with annealing treatment. Essentially complete intermixing of Cu and Cr occurred upon annealing at 150⁰C for the Cr₂O₃/Cu film couple. Such layers are potential selective solar absorber coatings