Use of optically detected magnetic resonance to correlate germanium electron centers with UV absorption bands in X-ray irradiated germanosilicate glasses

Abstract

The relationship between paramagnetic defect centers and UV absorption bands simultaneously generated by ionizing radiation in Ge-doped SiO2 glass is investigated using magneto-optical techniques. A sample of 7.0 mol% Ge-doped SiO2 was exposed to X-ray radiation, which resulted in the formation of absorption bands centered at 4.4 eV and 5.7 eV as well as electron spin resonance (ESR) signals attributed to the Ge(1) and Ge(2) defects. To isolate paramagnetic contributions to the induced optical absorption, the magnetic circular dichroism absorption (MCDA) spectrum was measured at several different temperatures over the range 2.00-6.21 eV. The optically detected magnetic resonance (ODMR) spectrum was then obtained at 4.42 eV via microwave-induced changes in the MCDA signals in order to unambiguously correlate this optical transition with a particular ESR signal. The ODMR data indicates that the Ge(1) center is responsible for this absorption band, providing the first unequivocal correlation of ESR and optical properties for this defect. In addition, evidence of a weakly absorbing paramagnetic defect was found at 5.65 eV that appears to be related to the Ge(2) center.