Comparison of γ and β-ray irradiation effects in sol-gel Ge-doped SiO2

We report an experimental study on the comparison between the γ or β ray induced Ge related point defects in Ge doped silica. Silica samples doped with ∼2.2 1017 Ge atoms/cm3 produced with the sol-gel technique have been irradiated. The effects of the irradiation have been investigated by optical absorption, photoluminescence and electron paramagnetic resonance spectroscopy in order to evaluate the generation and the dependence on dose of the Ge(1), E'Ge, Germanium Lone Pair Center (GLPC) and H(II) point defects. No relevant differences between the concentrations of γ or β ray induced Ge(1) and E'Ge point defects have been observed. In addition, it is found that both irradiations are able to induce GLPC with the same dose dependence. The main difference regards the formation of H(II), that arise from the reaction of GLPC with H released by irradiation, their concentration being larger after γ irradiation. It is suggested that the larger efficiency of H(II) generation by γ ray is due to the specific mechanism involving H released by irradiation. At variance, for the other Ge-related defects, our data show that the same processes of formation of such centers are involved in γ or β ray irradiation.