STRUCTURAL ORIGIN OF THE 5.16-EV OPTICAL-ABSORPTION BAND IN SILICA AND GE-DOPED SILICA

The origin of the 5.16 eV absorption band observed in silica and Ge-do ped silica was studied using optical and electron spin resonance (ESR) measurements. The band was observed only in samples containing Ge, su ggesting that it is related to the Ge impurity in silica, while a lack of correlation between the ESR intensity of the induced hydrogen-asso ciated doublet and the absorption coefficient of the 5.16 eV band indi cates that it is not related to two-coordinated Si or Ge. The observat ion of the absorption coefficient increased as the square root of the Ge concentration demonstrates that the 5.16 eV band is not related to two-coordinated Ge defects but that it is an oxygen deficiency center of the divacancy type associated with Ge.