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 tempera ture have been studied by scanning tunneling microscopy and scanning t unneling spectroscopy (differential conductivity method). A characteri stic high conductivity triangular bridge between the corner hole cente r and the reacted adatom has been observed at a sample bias larger tha n + 1.5 V after SiH4 adsorption, clearly different from the modificati ons in the spatial distribution of the differential conductivity signa l induced by hydrogen adsorption alone. Likewise, the tunneling spectr a over this site show a characteristic increase of the dI/dV signal. T he spectroscopic data prove that after reaction both of the reaction p roducts, SiH7 and H, are adsorbed in close vicinity, in the corner hol e (SiH3) and on the adjacent Si corner adatom (H). The resulting corne r complex leads to the triangle-like feature in the electronic structu re.