It was recalled that, among the many point defects in film samples which were detected by means of electron paramagnetic resonance, 2 of them (at g = 2.0017 and g = 2.0027) appeared to be associated with high-temperature treatments in dry N. Earlier work had suggested that the former was a multiple O vacancy center, while the latter was postulated to be an impurity-related variant of the EX center. The model for the 2.0027 center was based upon its chemical properties, which closely mirrored those of the EX center. An additional contrasting feature of the 2 centers was revealed. It was found that, although the presence of O quenched the generation of the line at 2.0027, the density of the 2.0017 center was little changed by an oxidizing ambient. The latter observation cast doubt on proposed models for the generation of the associated center. The out-diffusion of O and/or the production of SiO were thought to generate this multiple-O vacancy center. However, neither appeared to occur in a flowing O environment. It was instead thought to be more likely that the detection of the center was linked to the elimination of a H-related species. The role of O in decreasing the 2.0027 center was unclear. It was proposed that, as the oxide grew, structural relaxation permitted EX defects to anneal. The O heat-treatment of as-grown films might then accelerate the relaxation and annealing processes.

M.E.Zvanut, T.L.Chen: Materials Science Forum, 1997, 239-241, 7-10