Character of the reaction between molecular hydrogen and a silicon dangling bond in amorphous SiO2

The passivation by diffusing H2 of silicon dangling bond defects (E′ centers, O3tSi•) induced by laser irradiation in amorphous SiO2 (silica) is investigated in situ at several temperatures. It is found that the reaction between the E′ center and H2 requires an activation energy of 0.39 eV and that its kinetics is not diffusionlimited. The results are compared with previous findings on the other fundamental paramagnetic point defect in silica, the oxygen dangling bond, which features completely different reaction properties with H2. Furthermore, a comparison is proposed with literature data on the reaction properties of surface E′ centers, of E′ centers embedded in silica films, and with theoretical calculations. In particular, the close agreement with the reaction properties of surface E′ centers with H2 leads to the conclusion that the bulk and surface E′ varieties are indistinguishable from their reaction properties with molecular hydrogen.