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 positio ns in the vibrational spectra of hydrogen are sensitive to the surface structure and can be used for the experimental in situ analysis of th e growing CVD diamond phase. The differences in the spectral features corresponding to the CH bending vibrations have been correlated with t he results of the vibrational energy relaxation rate estimates. We fin d that the major contributions to the lifetimes of the excited CH stre tching states come from the anharmonic coupling between the CH stretch ing 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 o f the motion induced by the symmetric and antisymmetric stretching exc itation on C{100}/(2 x 1)H surface have been performed and the reasons for the unstability of the pure antisymmetric vibrations are discusse d. (C) 1997 Elsevier Science B.V.