Mechanism of radiation-induced defects in SiO2:: The role of hydrogen

Hydrogen related defects in anhydrous "dry", hydrated "wet" and hydrogen implanted amorphous silicon dioxide (a-SiO2) layers are investigated using cathodoluminescence (CL) technique in a wave length range 200-800 nm at specimen temperatures between room and liquid nitrogen temperature. Particular defect centers have been identified including the non-bridging oxygen hole center (NBOHC) associated with the red luminescence at 650 nm (1.9 eV) and the oxygen deficient centers (ODCs) with the blue (460 nm; 2.7 eV) and UV band (290 nm; 4.3 eV). An additional luminescence band Y in the green-yellow region has been clearly detected in hydrogen-implanted as well as in oxygen-deficient samples. The red luminescence shows quite different CL dose behavior in wet and hydrogen-treated samples due to dissociation and re-association of mobile hydrogen and oxygen from and to the NBOHC. The yellow luminescence at 580 nm (2.1 eV) is discussed in terms of radiolytic water dissociation as well as of ODC's in form of small silicon aggregates in the silica matrix. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.