Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 31: Clean surfaces II

O 31.3: Talk

Tuesday, March 27, 2012, 11:00–11:15, A 060

Vibrational spectra of reconstructed Si(100) surfaces — •Charles H. Patterson — School of Physics, Trinity College Dublin, Dublin 2, Ireland

We present calculations of vibrational spectra of IR-active modes at the Si(100) (2x1), p(2x2) and c(4x2) surfaces and the (2x1)-H surface. Previous calculations of phonons at these surfaces have not included scattering cross-sections. In contrast to existing hypotheses regarding relative scattering cross-sections for vibrational motions parallel or perpendicular to the surface, we find that the largest scattering cross-sections for the clean surfaces are for motions parallel to the surface. This is because parallel motions of chemically unsaturated dimers are accompanied by large charge transfer between dimer atoms which is relatively weakly screened by the less polarisable bulk semiconductor. Results of calculations are compared to HREELS data for the clean and H-covereved Si(100) surfaces and some suggestions for new experiments are made.