Growth mechanism and the order of appearance of diamond (111) and (100) facets

Experiments with local gas feeds of methane or acetylene indicate that both ${\mathrm{C}}_2$ ${\mathrm{H}}_2$ and ${\mathrm{CH}}_3$ contribute to the growth of (111) surfaces, whereas only ${\mathrm{CH}}_3$ contributes to that of the (100) surface. High-resolution electron-energy-loss spectroscopy has been used to investigate the termination modes of grown diamond (111) and (100) facets. The diamond (111) facets grown at 800 °C and 0.2% ${\mathrm{CH}}_4$ consist of (111) faces and {110} steps; atomic deuterium first replaces the hydrogen atoms adsorbed on (111) faces, and the growth rate of (111) facets is controlled by the concentration of ${\mathrm{C}}_2$ ${\mathrm{H}}_2$ at the film surface. After further growth of grown diamond (111) facets at 0.2% ${\mathrm{CH}}_4$ of local feed for 30 min, ${\mathrm{CH}}_3$ vibrational modes on (111) facets have been detected. The diamond (100) facets grown at 800 °C and 1.0% ${\mathrm{CH}}_4$ are terminated with ${\mathrm{CH}}_2$ radicals. Besides the ${\mathrm{CH}}_2$ vibration loss, CH bend loss of monohydrogenated dimer is detected for the (100) facets grown at 1000 °C. Based on the above results, it is suggested that the morphology of diamond film is controlled by the ratio of ${\mathrm{C}}_2$ ${\mathrm{H}}_2$ to ${\mathrm{CH}}_3$ concentration at the film surface. The higher the ratio, the faster the (111) facets grow, and thus (100) facets will be shown. Otherwise, (111) facets appear. This explains the rule of diamond crystalline appearance very well.