Influence of geometry factors of in situ dc glow discharge on the diamond nucleation in a hot-filament chemical vapor deposition system

The influence of geometry factors, including the discharge power density and the area ratio of the substrate Si to the cathode electrode, of an in situ dc glow discharge with and without hot-filament activation on the nucleation of diamond films on mirror-polished silicon substrates has been investigated. The nucleation density of diamond films on the center and at the edges of substrate was strongly enhanced by dc glow discharge pre-treatments. However, there was a great difference in the nucleation density on the center and at the edges of the substrate surface due to the secondary discharge at the edge. This difference was related to the dc discharge power density and the electrode geometry factor Φ. Oriented nucleation occurred at the edges under the conditions of higher dc discharge power density. The nucleation enhancement was attributed to the formation of graphite or amorphous carbon during the pre-treatment step.