Showing papers by "Wolf Gero Schmidt published in 1995"

III-V(110) surface dynamics from an ab initio frozen-phonon approach

Abstract: We have applied the ab initio pseudopotential frozen-phonon approach to study phonon frequencies and eigenmodes for III-V(110) surfaces. For GaAs our results at the \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} and X\ifmmode\bar\else\textasciimacron\fi{} points are in good agreement with data from recent high-resolution electron-energy-loss spectroscopy and He-scattering experiments. In the energy range of the controversially discussed ${\mathit{A}}_{1}$ phonon we observe an eigenmode with large atomic amplitudes at the surface, which, however, is mixed with bulk states. In order to investigate the chemical trend, additional calculations for surface \ensuremath{\Gamma}\ifmmode\bar\else\textasciimacron\fi{} phonons of InAs, GaP, and InP are presented. We observe a rather similar dynamical behavior for all these surfaces with modifications mainly due to the different masses of group-III and -V elements.

Hydrogen interaction with Sb-terminated GaAs and InP (110) surfaces.

Abstract: The interaction of atomic hydrogen with InP(110) and GaAs(110) surfaces terminated with a well-ordered antimony monolayer was investigated using spectroscopic ellipsometry and Raman spectroscopy. The characteristic features of the surface dielectric function associated with the Sb monolayer and the Raman lines from the excitation of surface vibrational modes disappear with increasing hydrogen exposure, indicating the etching of the Sb monolayer. No additional structure in the surface dielectric function and no shift in the phonon frequencies were detected during the etching process. By comparing the experimental results with ab initio calculations we conclude that the etching of the Sb monolayer starts at defect sites of the Sb monolayers and then propagates through the Sb surface chains.