Self-Trapped Excitons in Silicon Dioxide: Mechanism and Properties

Abstract

Irradiating silica produces self-trapped excitons (STEs) that spontaneously create atomic-scale distortions on which they localize themselves. Despite enduring interest in STEs and subsequent defects in this key technological material, the trapping mechanism and geometry remain a mystery. Our ab initio study of STEs in $\alpha$-quartz using a many-electron Green’s function approach answers both questions. The STE comprises a broken O-Si bond with the hole localized on the defected oxygen and the electron on the defected silicon atom in a planar $s{p}^2$ conformation. The results further explain quantitatively the measured STE spectra.