CHEMISORPTION STUDIES OF CHLORINE AND FLUORINE ON THE SILICON (111) SURFACE

Electronic energy structure calculations were performed for a 12-layer slab of Si (111) with and without monolayer of adsorbates. Overlapping Gaussian-fitted atomic potential with Slater's X alpha -exchange approximation was employed to approximate the crystal potential. Using alpha equals 0. 9 we obtained non-self-consistent band structure and density of states for relaxed Si(111) and Si(111) -Cl which are in good agreement with the results of experiment and other theoretical calculations. Having established the reliability of our approach on these well-known systems, we applied our method to the more reactive and technologically important Si/F system. We investigated both onefold and threefold sites for F chemisorption and found a net charge transfer of minus 0. 8e to F on both of these sites. More importantly, we found marked differences in the location of F(2p) -related levels for the two sites.