Structural relaxation and long-lasting phosphorescence in sol-gel-derived GeO2 glass after ultraviolet light irradiation

We report on the observation of a long-lasting phosphorescence phenomenon in GeO2 and Er3+-doped GeO2 glass samples fabricated by the sol-gel method. Absorption spectra showed that there were oxygen-deficient defects associated with Ge ions in the samples. Irradiation with ultraviolet light at 254 nm induced long-lasting phosphorescence with a peak at 465 nm for the GeO2 glass sample. The intensity of the phosphorescence decreased with increasing temperature and in inverse proportion to the time after a quick decrease of the intensity. The long-lasting phosphorescence in these samples is considered to be due to the thermally activated electron-hole recombination at room temperature.