The vacuum ultra-violet stimulated evaporation of amorphous material, and the formation of O vacancy defects in the latter, was found to be temperature dependent. At temperatures below 500C, surface O atoms were depleted, a SiOx layer formed, and the amorphous material was etched at a constant rate by the photon-stimulated desorption of constituent atoms. At temperatures of between 500 and 700C, the amorphous material itself decomposed and evaporated by forming SiO molecules. A thick layer that did not evaporate accumulated on the surface and reduced the rate of evaporation. At temperatures above 700C, evaporation of the amorphous material proceeded at a constant rate and maintained the surface stoichiometry at SiO2. Any SiOx layer which was created then vanished instantly.

H.Akazawa: Physical Review B, 1995, 52[16], 12386-94