First principle calculations of the optical properties of a neutral oxygen vacancy in Ge-doped silica

Abstract

We report ab initio configuration interaction calculations of the optical properties of a neutral oxygen vacancy in Ge-doped silica. This defect center, V(SiGe), is assumed to involve a missing O atom between a Si and a Ge atom with formation of a direct SiGe bond, SiGe. Several calculations have been performed using cluster models to obtain a reliable estimate of the excitation energy. The lowest fully allowed singlet–singlet transition in V(SiGe) occurs in a spectral region around 7.3 eV according to the calculations, i.e. not too far from the absorption band at 7.6 eV attributed to a V(SiSi) center in pure silica. The emission properties of V(SiGe) and the reasons for the similar transition energy in V(SiSi) and V(SiGe) centers are discussed.