Ultra-nanocrystalline diamond (UNCD) films prepared by microwave plasma enhanced chemical vapor deposition were implanted using 0.3 MeV nitrogen ions under a dose of 1013, 1014, and 1015 ions cm− 2. While the surface morphology of the UNCD films was not pronounced modified, the crystallinity of the films was changed appreciably due to ion implantation. The scratch test has been used to study the adhesion of the film to the substrate, which illustrated that the critical load, used as a measure of the adhesive strength, is found to increase with ion dose. Secondary ion mass spectroscopy (SIMS) analyses on the interfacial morphology indicated that the main factor in improving the adhesive strength is the modification on interfacial structure through inter-diffusion between film and substrate.
