MICROSCOPIC THEORY OF ELECTRON TRANSITIONS AT SI(111)-7X7 - OPTICAL-PROPERTIES AND ENERGY-LOSS SPECTRA

We have calculated the electronic and optical properties of the Si(111 )-7 X 7 surface within the dimer-adatom stacking fault (DAS) model. Ba sed on the theoretical surface band structure we have determined the d ifferential reflectivity (DR) between clean and hydrogenated surfaces for s- and p-polarized light. The electron energy-loss (EEL) spectrum has also been calculated. Theoretical findings, interpreted in terms o f electron transitions, agree well with the main experimental peaks ob served in DR and EEL spectra.