Deposition of nanocrystalline diamond films on silicon nitride ceramic substrates using pulsed microwave discharges in Ar/H2/CH4 gas mixture

Silicon nitride (Si3N4) ceramics coated with nanocrystalline diamond (NCD) films are promising materials for tribological applications. In this work, NCD films are deposited on Si3N4 ceramic substrates in pulsed Ar/H2/CH4 microwave discharges. Comparisons with films elaborated in continuous mode on Si3N4 and Si substrates, and on Si substrates in pulsed mode are achieved. The results give evidence for the growth of diamond films with a relatively high growth rate above 1 μm/h. Good nanocrystalline features are obtained, with a small grain size below 20 nm and a surface roughness lower than 40 nm. The paper emphasizes that the great interest of the pulsed mode is to enable the deposition of good-quality NCD films on ball-shaped Si3N4 ceramics, by preventing the graphite formation observed in continuous regime due to a high plasma heating. Pulsed microwave discharges are then hopeful processes for treating complex-shape Si3N4 ceramics appropriate for specific tribological applications.