Microstructure evolution in diamond CVD: Computer simulations of 111 surface site formation on a growing diamond-100 surface

A Monte Carlo simulation strategy was used to explore the kinetics and mechanisms of 111-surface site formation on a growing diamond-100 surface. The starting point of the simulations was a 30 x 30 carbon atom array with the structure of an ideally reconstructed, Diamond-(100)-(2 x 1) surface. The growth mechanism included 69 reactions relevant to diamond growth from CH3, H, and H-2. Several of the growth steps involved migration of C-1-containing fragments across a diamond surface. The simulations were run for growth conditions similar to those found in hot filament and microwave plasma diamond chemical vapor deposition (CVD) reactors. The temperature and gas-phase composition were varied to investigate the dependence of 111-surface site formation on growth conditions. The extent of 111-surface site formation was inferred from the height distributions of films that had been grown to mean heights of 10 carbon monolayers. Results of the simulations imply that, for typical hot filament and microwave plasma conditions, 111-surface site formation increases with growth temperature, decreases with H-atom concentration, and is relatively independent of methyl concentration. Much of the temperature and composition dependence vanishes when reactions allowing for carbon surface migration are prohibited. It is concluded that surface migration plays an important role in microstructure development in diamond CVD.