Photon-Induced Redox Reactions in Amorphous Materials

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Thermal decomposition reaction of <TO_2> (T=Sior Ge) melts at high temperature and photon-induced redox reactions related to Ge or P in <SiO_2> glasses were studied by use of ESR, Raman scattering, optical absorption and photo-luminescence. A model reaction was proposed which can totally explain formation of the defects detected in <SiO_2> or <SiO_2> : <GeO_2> glasses. They are E', NBOHC, T-T homobonds, peroxy linkages (or O-O homobonds) and T O or T( <II> ) species. The initial reaction is radical decompositionof T-O bonds at high temperatures and the defects are product of secondary reactions between the initial radical species. The net reaction is expressed as <2TO_2> 2TO+ <O_2> , Which predicts the dependence of concentration of the radical species on <pO_2> during glass preparation.Germanium traps an electron upon low temperature-irradiation of the glasses with -ray and the positive hole is trapped on an oxygen. This is similar to the results for the phosphorus-doped glasses.