Oxidation of hydrogenated Si(111) by a radical propagation mechanism

F. A. SORIA; E. M. PATRITO; P. PAREDES OLIVERA

AMER CHEMICAL SOC

Lugar: Washington; Año: 2012 vol. 116 p. 24607 - 24607

he reactivity of the hydrogenated Si(111) surface toward H2O and O2 was investigated in order to elucidate the mechanism of oxidation of the first silicon bilayer in air. Density functional theory calculations were performed to identify elementary reaction steps and their corresponding activation energy barriers. The perfect surface is unreactive toward H2O and O2 at room temperature as deduced from the high energy barriers found. However, isolated Si dangling bonds, (Si3)Si·, surrounded by SiH groups, readily react with O2 (but not with H2O), producing a silanone intermediate of the form (Si2O)SiO· where one of the silicon back bonds is oxidized. This intermediate is reached after a series of elementary steps with very small activation energy barriers. In the next step, the oxygen atom of the silanone group inserts into a Si–Si back bond, and the surface silicon dangling bond is regenerated as a (SiO2)Si· moiety in which the silyl group has two oxidized back bonds. This initiates a s