Reactions of SiCl groups in amorphous SiO2 with mobile interstitial chemical species: Formation of interstitial Cl2 and HCl molecules, and role of interstitial H2O molecules

Abstract

Reactions of the network-bound chloride (SiCl) groups in amorphous SiO2 (a-SiO2 or SiO2 glass) with mobile interstitial oxygen (O2), water (H2O), and hydrogen (H2) molecules thermally loaded from ambient atmosphere and with mobile radicals created by exposure to F2 laser light (λ=157nm,hν=7.9eV) were investigated. Reactions of the SiCl groups with O2 and H2O produce interstitial chlorine (Cl2) and hydrogen chloride (HCl) molecules, respectively. An infrared-absorption band appearing at ∼2815cm−1 is assigned to the interstitial HCl. The SiCl groups do not react with H2 below 400°C. However, sequential gas loading first with O2, then with H2 leads to the production of interstitial H2O, which decomposes the SiCl groups into HCl. Furthermore, the formation of the interstitial HCl with exposure to F2 laser light, most likely due to the cracking of the Si–Cl bonds with photogenerated hydrogen atoms (H0), was demonstrated. These findings yield a general picture of the reactions of the chlorine-related species in a-SiO2 and demonstrate the significant influence of even minor amounts (<1018cm−3) of interstitial H2O on defect formation and annihilation processes.