Growth and characterization of nanocrystalline diamond/amorphous carbon composite films prepared by MWCVD

Nanocrystalline diamond films in an amorphous matrix have been deposited by microwave plasma chemical vapour deposition from CH 4/N 2 mixtures and characterized with respect to their morphology and structure, composition, crystallinity and bonding structure. The films turned out to be nanocrystalline with crystallite sizes on the order of 3–5 nm and a density of 2.75 g/cm 3. They contain approximately 0.5–1% nitrogen and 10% hydrogen. The nitrogen content of the gas phase has a strong influence on the growth rates and the morphology of the films, whereas the bonding structure is almost unaffected. Raman spectra prove the existence of sp 2 bonded carbon in the matrix; however, according to electron energy loss spectroscopy and X-ray photoelectron spectroscopy investigations the sp 2 content is rather small. Infrared spectra show that the hydrogen is bonded primarily in the form of sp 3 CH x groups.