Energy levels of self-trapped holes in amorphous SiO₂: Fictive temperature dependence

Fictive temperature (T_f) dependence of self-trapped holes (STHs) in low temperature UV-irradiated silica glasses was systematically investigated by the electron spin resonance (ESR) method. The decay of the ESR signals was found to be bleaching photon energy dependent and to follow the stretched exponential decay function at each bleaching wavelength. When the one-photon process is dominant during the photo-bleaching process, where the recombination of electrons excited from the valence band with the holes in the STH band results in the decay of STH signals, the energy levels of STH₁ were thus derived at 1.75 0.02 eV, 1.61 0.03 eV, 1.45 0.05 eV and STH₂ at 1.68 0.02 eV, 1.44 0.02 eV, 1.25 0.04 eV, respectively, for T_f = 1500, 1350 and 1200 °C samples.