Nature and origin of the 5-eV band in SiO2:GeO2 glasses.

The sources of an absorption band at ∼5 eV observed in SiO 2 :GeO 2 and GeO 2 glasses have not been unambiguously identified. Results reported here are consistent with the source of two types of neutral oxygen vacancies. Samples of 95SiO 2 :5GeO 2 and 90SiO 2 :10GeO 2 were prepared by a chemical vapor deposition soot-remelting method. Optical-absorption and electron paramagnetic resonance spectra were measured. An absorption band centered at 5 eV in as-prepared SiO 2 :GeO 2 glasses is composed of two components