Local Field Contributions to the Bond-Stretching Frequencies of Si–H and Si–H2 Groups on Singular and Vicinal Si(111)

Abstract

Short-range valence forces, and dynamic effects due to dipole–dipole interactions have been used to calculate the bond-stretching frequencies for bonded H (and D) on flat and vicinal Si(111) surfaces. Dipole–dipole interactions have been calculated exactly for flat surfaces and for vicinal surfaces off-cut in the 112- and 1-1-2 directions terminated respectively by monohydride, Si–H, and dihydride, Si–H2, bonding groups at the step edges. Using short-range force constants and effective charges obtained from isolated Si–H and Si–H2 stretching modes in hydrogenated amorphous Si, a-Si, the calculated coupled mode frequencies are in excellent agreement with experiment.