High quality homoepitaxial diamond thin film synthesis with high growth rate by a two-step growth method

Homoepitaxial diamond films grown in the condition of CH4/H-2 ratio lower than 0.15% in a microwave-assisted plasma chemical vapor deposition system had excellent electrical and optical properties without any unepitaxial crystallites (UCs). Under such a low CH4 concentration condition, however, the growth rate becomes too slow to obtain a useful thickness. In order to overcome this problem, we attempted a two-step growth method. In the first step the substrate surface was treated by homoepitaxial growth of diamond in the presence of 0.05% CH4 in H-2; in the second step the CH4 concentration was increased. By considering the origin of UCs with cross-sectional transmission electron microscope studies, it was found that this method is based on surface improvement of the initial substrate by means of ultra-low CH4 concentration growth. This method was quite useful for obtaining high quality films, with high growth rate and reproducibility. (C) 1999 Elsevier Science S.A. All rights reserved.