Photoluminescence of Intrinsie Defects in Glassy GeO2. Twofold Coordinated Ge and Nonbridging Oxygen

Photoluminescence (PL) bands at 4.1 eV with decay time τ < 20 ns and at 3.0 eV with τ = 78 μs are excited in the oxygen defieiency-related optical absorption band at 5.06 eV. These PL bands are closely similar to the PL bands in Ge-doped glassy SiO2. They are attributed to the transitions from 1B1 and 3B1 excited states of a twofold coordinated Ge atom (Ge center). In reaction with atomic hydrogen this PL center converts to the well-known paramagnetic “H(II)” center charcterized by hydrogen hfs of 12.0 mT. γ-irradiation of glass GeO2 induces a PL band at 1.84 eV with τ = 4.6 μs, which similarly as in glassy SiO2 is ascribed to the non-bridging oxygen hole centers.