Ge related centers induced by gamma irradiation in sol–gel Ge-doped silica

Investigation of sol–gel silica samples with different Ge-doping content and with concentration of oxygen deficient centers (ODC) less than 1016 centers/cm3 was carried out after γ ray irradiation by electron paramagnetic resonance, optical absorption (OA) and photoluminescence measurements. It is found that in the dose range below 5 kGy paramagnetic centers with the characteristic resonance line of Ge(1) defects are induced in all the investigated samples, whereas no signatures of other Ge related centers or E′-Si are detected. Optical measurements detect two absorption bands peaked at 4.5 and 5.8 eV and no variation in the emission spectra of highly doped materials. From these results new suggestions arise for the correlation between the Ge(1) centers and the OA bands at 4.5 and 5.8 eV and for the absence of correlation of Ge(1) with Ge-ODC.