Molecular Diffusion in a-SiO2: Its Role in Annealing Radiation-Induced Defect Centers
The reversible annealing of E' centers (paramagnetic bridging oxygen vacancies) in a-Si02 at temperatures lower than about 300°C was studied by electron paramagnetic resonance (EPR) spectroscopy in samples of bulk dry a-SiO2 which were specially prepared with widely differing amounts of dissolved O2. It was found that all decreases in E' concentrations were exactly matched by increases in corresponding SiOO- (superoxide radical) concentrations, and that there was a pronounced persistence of E' centers at higher temperatures in oxygen-deficient samples. The annealing process was modelled by a diffusion-limited quasi-unimolecular reaction between dissolved O2 and fixed trapping centers in the context of the continuous time random walk (CTRW) formalism.
KeywordsElectron Paramagnetic Resonance Continuous Time Random Walk Spin Concentration Annealing Kinetic Degas Sample
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