The interface between diamond-like amorphous hydrogenated carbon (a-C : H) and A1,03 was analysed by sputter depth profile analysis via x-ray photoelectron spectroscopy. X-ray photoelectron spectra were also recorded during direct ion beam deposition (CH4, E = 400 eV) monitoring the initial build-up of the interface. No stoichiometric interface compound was detected, although Al,O, is reduced to A1,0,-, (x -0.5-1) enabling an interaction with the carbon atoms. This results in an excellent adhesion of a-C : H to the chemically inert A1,03.