Ultrananocrystalline Diamond / Amorphous Carbon Composite Films – Deposition, Characterization and Applications

UNCD/a-C composite films have been deposited by microwave plasma chemical vapour deposition from methane/nitrogen mixtures with 17% CH4 in the temperature range 500-770 degrees C on various substrates such as monocrystalline silicon wafers, polycrystalline diamond, c-BN, TiN, GaAs, and other materials of technological interest. The resulting films have been thoroughly characterized with respect to their morphology, crystallinity, composition, and bonding structure. It was found that they are composed of diamond nanocrystallites (3-5 nm in diameter) surrounded by 1-1.5 nm amorphous carbon grain boundary material; the ratio of the volume fractions of crystalline and amorphous phase is close to unity. The investigations of the application-relevant properties of the UNCD/a-C films revealed that they are attractive for a number of mechanical, tribological, structural, and biomedical applications.