Structural changes induced by KrF excimer laser photons in H₂-loaded Ge-doped SiO₂ glass

Photochemical reactions related to the Ge lone-pair center (GLPC) that are induced by KrF excimer laser photons in H₂-loaded Ge-doped SiO₂ glass have been investigated. Without the H₂ loading, the Ge electron center (GEC) and the positively charged GLPC were induced by the laser irradiation. In the H₂-loaded sample, the GEC, the Ge E′ center, and the germyl radical (GR) were induced by the irradiation, while the positively charged GLPC was not observed after the irradiation. If the H₂-loaded sample was thermally annealed after the photon irradiation, the concentration of the photo-induced GEC decreased monotonically with an increase in the annealing temperature. On the other hand, the concentration of the GR increased up to the annealing temperature of 160 °C, and it decreased at higher temperatures. Without the pre-irradiation, the induction of the GR was not observed even in the H₂-loaded sample. From these results, it is concluded that the positively charged GLPC is terminated with a hydrogen atom in the H₂-loaded sample and then becomes the GR by trapping an electron thermally released from the GEC.