Formation of optically active oxygen deficient centers in Ge-doped SiO2 by gamma- and beta-ray irradiation

We report an experimental study on the comparison between the c- or b-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 with c-ray or with b-ray. 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, GLPC (Germanium lone pair center) and H(II) point defects. No relevant differences between the concentrations of c- or b-ray induced Ge(1) and E’Ge point defects have been observed and, in addition, it has been found that both irradiations are able to induce GLPC with the same dose dependence. By contrast, the main difference regards the formation of H(II) centers, their concentration being larger after c irradiation. It is suggested that the larger efficiency of H(II) generation is due to the specific mechanism involving H released by irradiation, whereas the similarity of the formation of other Ge related defects speaks for the occurrence of identical mechanisms induced by c or b irradiation.