Reflectance anisotropies of silicon surfaces: Analysis of spectra in terms of surface excess susceptibilities

Reflectance anisotropy (RA) spectra of semiconductor surfaces provide a measure of the contribution of the outermost atomic layers of the solid to the optical reflectivity. Experimental RA spectra are not yet well understood and a suitable means of analysis is needed. Interpretation of features of RA spectra in terms of the surface excess susceptibility is argued to be preferable to interpretation in terms of transitions between occupied and unoccupied states at the surface. RA spectra of the unreconstructed Si(001) and Si(110) surfaces are calculated using the discrete dipole method and these are analysed in terms of surface excess susceptibilities and surface polarization.