Surface second-harmonic generation from Si(111)(1x1)H : theory versus experiment

Comparing calculations of the second-harmonic generation (SHG) from the monohydride-terminated Si(111)(1x1)H surface with experimental spectra covering the two-photon energy range from 2.4 eV to 5.0 eV, we present a quantitative test of available state-of-the-art theory of surface SHG from a well-characterized semiconductor surface. We conclude that the density-functional theory within the local-density approximation approach with quasiparticle corrections leads to a semiquantitative agreement between theory and experiment and that the SHG arises from transition across bulk states which are perturbed by the surface. The calculations show that the spectra are sensitive to relaxations of the second-layer Si atoms.