Correlation of the 5.0- and 7.6-eV absorption bands inSiO2with oxygen vacancy

Bleaching of optical activity induced by UV laser exposure in natural silica

“…We stress that UV irradiation induces a change of the ratio between the intensities of the emission bands at 3.14 eV and 4.28 eV: this ratio, measured to be 5.1±0.4 before irradiation, increases of ~30 % after 3000 laser pulses. In the inset, we report the effect produced by laser exposure on absorption spectrum where one observes a partial bleaching of a band peaked at 5.12±0.02 eV, FWHM= 0.45±0.03 eV (B 2β band [12]). …”

Synthesis and Cathodoluminescence of Morphology-Tunable SiO2 Nanotubes and ZnS/SiO2 Core−Shell Structures Using CdSe Nanocrystals as the Seeds

“…58,59 For example, the 2.7 eV band is ascribed to the neutral oxygen vacancy (≡Si-Si≡), and the 3.0 eV band corresponds to some intrinsic diamagnetic defect center, such as the two-fold-coordinated silicon lone-pair centers (O-Si-O). 60 These defects are clearly due to high oxygen deficiency. These structure defects are radiative recombination centers.…”

Photosensitive defects in silica layers implanted with germanium ions

“…After the spectra were resolved, concentrations N of the corresponding emission-active centers in the surface layer of the test material were determined from the intensity of each band using a modified Smakula formula in the emission form [4]:…”

“…The only evident fact is that all these bands correspond to some types of oxygen-deficient centers (ODC's). For example, the 5.02 and 5.15 absorption bands in pure SiO 2 (frequently referred to as B 2a and B 2b ) are related to an oxygen vacancy "Si-Si" ðV 0 O Þ and a twofold-coordinated silicon atom @Si: ðSi 0 2 Þ, respectively [4,5]. A similar qualitative picture was observed in silica-germanate [6], but the 5.06-and 5.16-eV absorption maxima there were related to a vacancy "Ge-Ge" and a twofold-coordinated Ge 0 2 atom.…”