Identification of Native Defects in a-SiO2

One of the most powerful experimental tools for the identification of defects in solids is electron paramagnetic resonance (EPR). In a-SiO₂, however, the defects are diamagnetic in their ground state, and are therefore invisible to EPR. Because of this, researchers interested in the structure of defects in SiO₂ have had to rely on the use of ionizing or heavy particle radiation (γ, e-, n, X,..) in order to generate paramagnetic defects which can then be detected by EPR1. While these studies have been very fruitful, and the question of the mechanism by which defects are generated in a glass by the influence of high-energy radiation is an interesting and important one2, they leave open a fundamental question. Namely, since ionizing radiation may create additional structural defects in the glass, either by direct knock-ons or by a radiolytic process such as a recombination-assisted reaction, one gains little or no information about the native defects present before irradiation. The identity and properties of these native defects in a-SiO₂ are important both for technological reasons, and because they help us to understand the nature of glasses in general.