Gas-phase room-temperature oxidation of (100) silicon

A microscopic model is proposed for explaining the kinetics of gas-phase (O2 or O2:H2O) room-temperature oxidation of single crystalline (100) silicon. The formation of the first oxide layer is described in terms of oxidation by O2 of weak SiSi backbonds to surface Si(OH)2 groups. The growth of a thicker oxide, which occurs in a layer-by-layer fashion, is described as the final result of a set of hydroxylation-oxidation cycles, whose rate-determining step is cleavage by water of peroxidic bridges at the SiSiO2 interface. After the first monolayer, this process requires thermally assisted tunnelling of the proton from an adsorbed H2O molecule at the SiO2 surface to an oxygen bridge at the interface followed by OH− drift to the proton-hosting site.