The water adsorption on the Si(111) 7 × 7 surface: a theoretical study

Abstract

We present a theoretical study of the initial steps of the water adsorption on Si(111)7 × 7. Water dissociates on the surface. In a first step, partial dissociation generates the radical species H · and HO · which are adsorbed on the dangling bonds of the surface. The first sites to be saturated are those of adatoms from the faulted half of the Si(111)7 × 7 unit cell. When three molecules per unit cell are adsorbed, one rest-atom site is involved together with adatom sites and the adsorption implies an electron transfer from one unit cell to another. For the subsequent adsorptions, a rest-atom site is involved simultaneously with an adatom site. The OH · goes on the rest-atom site since H ·, which is more selective, goes preferentially on the adatom site. Complete dissociation of H 2O seems to be even more favorable. Water adsorption can displace the adsorbed hydrogen atoms, initiating an oxidative process.