Dynamic effects in energetic particle-induced luminescence of SiO 2

Abstract

Dynamical measurements of ion-induced luminescence and in-reactor luminescence of SiO 2 glass have been performed. First the dynamic effects of the ion-induced luminescence are compared between D + and He + ion irradiations, and then the time evolution of the in-reactor luminescence change with neutron fluence is compared with that observed in the ion-induced luminescence. Finally, the origin of the luminescence center is discussed. The luminescence spectra of silica glasses induced by D + and He + irradiation have been found to be very similar to cathodoluminescence originating from the centers associated with oxygen vacancies, and the intensity is proportional to the deposited energy by electron excitation irrespective of the incident ion species. The luminescence intensity changes with ion fluence, first increasing, then reaching a maximum and finally decreasing to the nearly steady value after prolonged irradiation. When the fluence is converted to displacement per atom (dpa) value, changes of the luminescence intensity under D + and He + irradiations are very similar. From dynamical change of the luminescence intensity, the first increase of the luminescence intensity is attributed to the increase of newly produced point defects or to an oxygen deficiency due to atomic displacement. The observed decrease is attributed to the association of the point defects, for example, formation of segregated Si or more complex defects. In-reactor luminescence also reveals an intensity increase caused by neutron-induced displacement. The present work clearly demonstrates that dynamic measurement of the ion-induced luminescence can give detailed information on the processes of defect formation in optically transparent materials.