Character, mechanism of formation and transformation of point defects in type IV silica glass

Abstract

In the temperature range 600–650°C, transformations of defects in quartz glass are observed. The dependence of a band at 163 nm on annealing temperature is measured. Changes of structure in this temperature range are observed for the SiH and SiOH centers. These are caused by the appearance of a structural relaxating process at ∼ 675°C, the character of which is not determined. It is shown that the band at 163 nm is caused by three-coordinated non-paramagnetic silicon Si 3 + (T 3 + center). The band at 248 nm is attributed to an oxygen vacancy SiSi. It is shown that at temperature < 650°C the formation of SiH centers (absorption band at 2254 cm −1) is due to the interaction of H 2 with oxygen vacancies. At temperatures > 650°C, the interaction of H 2 with T 3 + centers was achieved. The maximum of the band of the SiH centers thus formed is at 2264 cm −1. It was assumed that, in the type IV glass, the formation of SiOH is due to an interaction of H 2 with peroxy linkages. Changes of the fundamental absorption edge are correlated with the changes of concentration of OH groups from 1500 ppm to 2 ppm. In the region < 2 ppm, the linear dependence of these changes on OH concentration is violated.