Vibrational dynamics of the CH stretching mode of H-terminated diamond surfaces

The vibrational dynamics of hydrogen on low-index diamond surfaces is studied by the molecular dynamics method using an empirical Molecular Mechanics (MM3) potential. We find that the CH stretching peak positions in the vibrational spectra of hydrogen are sensitive to the surface structure and can be used for the experimental in situ analysis of the growing CVD diamond phase. The differences in the spectral features corresponding to the CH bending vibrations have been correlated with the results of the vibrational energy relaxation rate estimates. We find that the major contributions to the lifetimes of the excited CH stretching states come from the anharmonic coupling between the CH stretching and CCH bending vibration modes. The latter is highly coupled with the substrate phonons which leads to the formation of broad spectral regions associated with CCH bending vibrations. The dynamic analysis of the motion induced by the symmetric and antisymmetric stretching excitation on C{100}/(2 x 1)H surface have been performed and the reasons for the unstability of the pure antisymmetric vibrations are discussed. (C) 1997 Elsevier Science B.V.