New Insight Into the Structure of SiO2 Glass from a Point Defect Study

Formation of defect centers in pure silica glass (a-SiO₂) depends greatly on the manufacturing process of the glass. Non-bridging oxygen hole centers (NBOHC: ≡Si-0•) are dominantly created by γ-ray irradiation in high OH-group content (≥ 700 ppm) silica made by the direct glass deposition process1. In low OH-group content silica made by the plasma or soot method, oxygen content in the glass strongly affects the defect formation2,3; drawing induced peroxy radicals, drawing induced NBOHC, ≥-ray induced peroxy radicals and the 1.52 μm band induced by hydrogen treatment are created in oxygen-rich silica, but the 5 eV (245 nm) band and drawing induced E′ center (≡Si•) are created in oxygen-deficient silica. Based on these experimental results, the authors proposed2 the defect in the form of ≡Si-Si≡ as a model of the oxygen deficiency. In the present paper, further experimental evidence which supports the authors’ model and its proof by numerical calculation are presented. The structure of glass is also discussed.