Synthesis and structural study of nano/micro diamond overlayer films

Abstract The nano/micro diamond overlayer films have been successfully fabricated by means of bias growth technique using microwave plasma-enhanced chemical vapor deposition method. During the diamond growth, as a negative bias (−100 V) is applied midway on the substrate side, the nanocrystalline diamond layer can be controllably deposited on the as-grown microcrystalline diamond to form a nano/micro overlayer structure. Transmission electron microscopy images reveal that the nanocrystalline layer consists of ultra-fine diamond crystallites, of which the average grain size is only about 4–5 nm. The formation mechanism of diamond nanocrystals on diamond micrograins under the bias conditions is discussed. Moreover, by the repeat-biasing way, three or more layered diamond films can be produced as well.