Chemical stability of nano-diamond films deposited by the dc-glow discharge process

The precursor for chemically vapor deposited diamond may be formed using a de-glow discharge process for in situ surface pretreatment. The promotion o f diamond deposition by this method is primarily due to the formation of na no-sized diamond particles. In the present work, we used hydrogen plasma ex posure as a chemical probe to study the nature and chemical stability of th e carbon precursor for diamond deposition formed by the dc-glow discharge p retreatment. This method is based on the difference in the etching rates of various carbon phases in hydrogen plasma. Graphitic and amorphous, sp(2)- as well as sp(3)-bonded, carbon structures undergo a very rapid etching pro cess. whereas the etching rate of diamond is negligible. The characterization of the deposited films was carried out using high-reso lution scanning electron microscopy (HR SEM) and near-edge X-ray absorption fine structure (NEXAFS). Based on the NEXAFS measurements, it is shown tha t the hydrogen plasma etching results in a relative decrease in sp(2)-bonde d carbon and a corresponding increase of the sp(3)-fraction in the nearsurf ace layer. The etching rate of nearly continuous nano-diamond films was fou nd to be ca 0.5 mu m/h. HR SEM observations show inhomogeneous character of the etching process. (C) 2000 Elsevier Science S.A. All rights reserved.