Spectroscopic evidence for valence-alternation-pair defect states in vitreous SiO2

Abstract

Two bands attributed to intrinsic defect states have been identified through studies of the infra-red and Raman spectra of pristine and neutron-irradiated vitreous (v-) SiO₂. Vibrations in the 900–950 em⁻¹ regime are assigned to non-bridging oxygen atoms (C₁-) in agreement with previous studies. It is demonstrated that the vibrations near 600 cm⁻¹, the origins of which have been uncertain up to now, can be assigned to three-coordinated oxygen atoms (C₃ ⁺). Thus the intrinsic defects are described in terms of the valence-alternation-pair model, previously applied to chalcogenide amorphous semiconductors.