AB-INITIO STUDY OF HYDROGEN ADSORPTION ON THE SI(111)-(7X7) SURFACE

First-principles total-energy pseudopotential calculations are perform ed to investigate the adsorption interaction of a H atom with dangling bonds on the Si(111)-(7 X 7) surface. The binding energies for adsorp tion of H at the adatom, rest atom, and corner hole sites are calculat ed to be 2.9, 3.2, and 3.5 eV, respectively. Spectral analysis of the electronic states shows that nonlocal changes of chemical reactivity a re induced by charge transfer upon H adsorption. It is found that H ad sorption on the adatoms or rest atoms induces a charge transfer onto t he Si-H bond and a shift in energy of the remaining dangling-bond stat es. Adsorption on the corner hole, however, does not involve any charg e transfer. The relationship between charge transfer and binding energ ies is discussed.