Synthesis and structural study of nano/micro diamond overlayer films

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. (C) 2002 Elsevier Science B.V. All rights reserved.