Room temperature disilane adsorption on Si(111) and Ge(111) studied by UPS: a comparative study

Abstract

Room temperature (RT) adsorption of disilane (Si 2H 6) on Si(111) andGe(111) surfaces has been studied using uv photoelectron spectroscopy (UPS). Si(111) and Ge(111) substrates were atomically cleaned under uhv conditions and subsequently exposed at room temperature to low pressure (10 −5 torr) Si 2H 6 doses. For both surfaces, only characteristic features or monohydride and polyhydride phases are evidenced. For RT disilane adsorption on Si(111), UPS spectra reveal solely polyhydride phase formation whereas Si 2H 6 adsorption on Ge(111) induces both mono and polyhydride phases. However, for equivalent exposure doses, UPS features associated to these two phases are significantly weaker on Ge(111) than on Si(111). For RT disilane adsorption on Ge(111), X-ray photoelectron spectroscopy (XPS) reveals no presence of silicon atoms on the Ge surface, even for heavy exposure doses. The monohydride and polyhydride phases are of comparable importance with those obtained by exposing a Ge(111) surface to molecular hydrogen. We conclude that the Ge(111) surface dissociates the H 2 molecule. The resulting H radicals saturate the available dangling bonds inhibiting the sticking of H 2SiSiH 2 radicals. We also checked that molecular hydrogen is not decomposed by the Si(111) surface. In that case, we explain the presence of an important dihydride phase without associated monohydride by the sticking of H 2SiSiH 2 groups.