6533b7d4fe1ef96bd1262623

RESEARCH PRODUCT

Site-selective luminescence study of defects. in gamma-irradiated glassy germanium dioxide

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Abstract Luminescence of γ-irradiated samples of GeO2 glass was studied using dye laser excitation in the wavelength region between 590 and 656 nm. An inhomogeneously broadened luminescence band with a peak around 1.86 eV, halfwidth of 0.16 eV and decay constant τ ≈ 5.1 μs was found. At temperatures below 20 K a resonance ZPL and a vibronic peak 710 cm−1 below the laser photon energy emerge when laser is tuned to energies between 1.95–1.89 eV. The site-selective luminescence spectra are qualitatively similar to those of the non-bridging oxygen hole center (NBOHC) in SiO2 glass and are attributed to NBOHC in glassy GeO2. The measured ratio between the energies of the observed local vibrations in GeO2 (710 cm−1) and SiO2 (890 cm−1) is close to the ratio, calculated on the basis of the known SiO and GeO central force constants and taking the reduced mass of SiO and GeO molecules for the mode mass. This confirms the assignment of the 710 and 890 cm−1 vibronic lines to the non-bridging oxygen stretching modes of the NBOHC in glassy GeO2 and SiO2 respectively.