CHEMISORPTION OF ATOMIC-HYDROGEN ON THE SI(111)7X7 RECONSTRUCTED SURFACE AT LOW-COVERAGE

We present a theoretical study of the chemisorption, at low coverage, of atomic H on the Si(111)7 X 7 reconstructed surface, using the cryst alline extension of the extended Huckel method. Hydrogen adsorption on surface dangling bonds eliminates the associated surface states near the Fermi level. Two main peaks, P-1 and P-2, appear. Their positions are in qualitative agreement with the experimental data. Densities of states (DOS) calculations emphasize the fundamental role of the dangli ng bonds of the adatoms in the formation of these peaks. Cluster model s show that the presence of peaks P-1 and P-2 is to be associated with an in-phase overlapping between the 1s H orbital and the 3p Si orbita l for P-1 or the 3s Si orbital for P-2. Another peak, P-3, might origi nate from the adsorption of hydrogen on the rest-atom dangling bonds.