Silicon-titanium-doped a-C:H, deposited via plasma assisted chemical vapor deposition and its chemistry at the titanium carbide interface has been studied via X-ray photoelectron spectroscopy In the a-C:H film, as well as at the interface, the carbide species TiSiC is formed. Thermal treatment of Si,Ti-a-C:H films on TiC causes an increase in TiSiC at the interface leading to a better adhesion performance. (C) 2003 Elsevier B.V All rights reserved.