Thermal and photochemical oxidation of Si(111): Doping effect and the reaction mechanism

It has been proposed that a ``harpooning''-like silicon-to-O₂ electron-transfer process to form an O₂^--like precursor is the crucial first step in the oxidation of Si(111). Here we use {δ} doping of silicon with boron to reduce the electron population of the silicon-surface adatom dangling bonds. We find that indeed the extent of oxidation and the amount of the O₂^--like species on the surface are greatly reduced by the doping. Moreover, we find an analogous suppression of the photo-oxidation process. The latter result indicates that the photodissociation of the same O₂^--like precursor is involved in the photoenhancement of the oxidation process.