Combined effects of argon addition and substrate bias on the formation of nanocrystalline diamond films by chemical vapor deposition

Abstract

The article reports combined effects of Ar addition and substrate bias on the grain size, microstructure, and growth rate of the diamond films prepared in microwave plasma-enhanced chemical vapor deposition. The nanocrystalline diamond (NCD) films with grain size of 50–100 nm, characterized by Raman spectra, scanning and transmission electron microscopy, were produced at 90–99 vol % Ar concentration under −50 V substrate biasing. The growth rate of the NCD films was 0.7–0.8 μm h−1, larger apparently than those grown by only Ar addition or by substrate bias effect alone. The NCD formation by various mechanisms is discussed, and a revised C2 insertion mechanism by the promotion of H+ ions is proposed to interpret the higher growth rate of the NCD films.