Optically detected magnetic resonance studies of exciton trapping by germanium in quartz

Optically detected magnetic resonance (ODMR) has been used to study X-ray-induced luminescence in undoped and Ge-doped alpha -quartz at low temperatures. For samples with low Ge (120 p.p.m.) doping levels, two distinct triplet states are observed corresponding to emissions at 440 and 490 nm. The triplet state associated with the 440 nm band has been previously studied in undoped alpha -quartz and assigned to a self-trapped exciton. The authors ODMR results show that the triplet state associated with the 490 emission is similar to that giving rise to the 440 nm emission and suggest that the 490 nm recombination occurs at a site where the Si is replaced by Ge. The 490 nm emission is dominant in crystals with a high (1700 p.p.m.) Ge doping level.