Nucleation and growth during the chemical vapor deposition of diamond on SiO₂ substrates

The early stages of microwave-plasma assisted CVD of diamond on fused silica and silicon substrates were investigated. Nucleation densities on fused silica were somewhat lower than on silicon; however, the diamond growth rates on fused silica were faster. These results suggest that the substrate alters the plasma chemistry near the substrate. Transmission electron microscopy showed a relatively smooth interface between the diamond grains and the SiO₂ surface. At low nucleation densities, the growth kinetics on both substrates were linear (i.e., the average feature size was proportional to the deposition time), which indicates that the growth kinetics were initially controlled by reaction(s) at the growing diamond surfaces. The transition to nonlinear growth kinetics observed at higher nucleation densities was probably caused by mass-transport limits.