MODIFICATION OF THE SI(111)-7X7 LOCAL ELECTRONIC SURFACE-STRUCTURE INDUCED BY SILANE ADSORPTION

The initial stages of SiH4 adsorption on Si(lll) 7 X 7 at room temperature have been studied by scanning tunneling microscopy and scanning tunneling spectroscopy (differential conductivity method). A characteristic high conductivity triangular bridge between the corner hole center and the reacted adatom has been observed at a sample bias larger than + 1.5 V after SiH4 adsorption, clearly different from the modifications in the spatial distribution of the differential conductivity signal induced by hydrogen adsorption alone. Likewise, the tunneling spectra over this site show a characteristic increase of the dI/dV signal. The spectroscopic data prove that after reaction both of the reaction products, SiH7 and H, are adsorbed in close vicinity, in the corner hole (SiH3) and on the adjacent Si corner adatom (H). The resulting corner complex leads to the triangle-like feature in the electronic structure.