Molecular dynamics simulations of CH3 sticking on carbon surfaces, angular and energy dependence

Sticking cross-sections for CH3 radicals at different angles of incidence and different energies were calculated using molecular dynamics simulations, employing both quantum-mechanical and empirical force models. The chemisorption of a CH3 radical at 2100 K onto a dangling bond is found to be highly dependent on the angle of incidence of the incoming radical. The sticking cross-section decreases from (10.4±1.2) to (1.4±0.3) Å2 when the angle of incidence of the methyl radical increases from 0° to 67.5°. A simple geometrical model is presented to explain the angular dependence. In the sticking process of CH3 radicals with higher kinetic energies (1, 5, and 10 eV) both a fully hydrogen-terminated surface and a surface with dangling bond were studied. The sticking probability is enhanced as the radical energy increases. We observed sticking onto the fully hydrogen-terminated surface for all cases except for the case when the methyl radicals had energies corresponding to a temperature of 2100 K.