Molecular-dynamics simulations of methyl-radical deposition on diamond (100) surfaces

We have performed molecular-dynamics simulations using realistic many-body semiclassical potentials for hydrocarbon interactions to investigate the deposition dynamics of hyperthermal CH₃ on diamond (100) surfaces. The adsorption probability was studied as a function of different incident radical and substrate conditions. Relevant energy exchange processes between incident molecules and the substrate were also analyzed. Three types of events were observed in the simulations: (i) adsorption events where CH₃ bonds onto a surface radical ``site,'' (ii) reflection events where CH₃ backscatters to the gas phase, and (iii) surface-hydrogen knock-out events at high incident CH₃ energy. The adsorption probability was found to be higher for normal incidence to the surface, and to increase for larger incident kinetic energies. The adsorption efficiency is not sensitive to surface H coverage except at lower CH₃ energies. No chemisorption of the radical on a surface that is fully hydrogen terminated is observed, indicating that a radical site is needed for the CH₃ to bind on the surface. Significant energy transfer through collision is observed.