On the natures of radiation-induced point defects in GeO_2-SiO_2 glasses: reevaluation of a 26-year-old ESR and optical data set

Abstract

26-year-old electron spin resonance (ESR) and optical data pertaining to isochronal annealing studies of x-ray induced defect centers in a GeO 2 -SiO 2 glass are revisited here with the object of extracting new insights regarding the fundamental natures of these defects. It is concluded that (i) the paramagnetic Ge(1) and Ge(2) centers are two energetically inequivalent configurations of a single trapped-electron defect, in analogy to what is known to be the case for the Ge(II) and Ge(I) centers respectively in α quartz [Isoya et al., J. Chem. Phys. 69, 4876 (1978)], and (ii) the germanium lone pair center (GLPC) stably traps holes only in pairs and hence remains ESR silent.