ELECTRON TRAP AND OPTICAL STORAGE STUDIES IN SrS:Eu AND SrS:Eu,Sm

Abstract

The electron traps in SrS:Eu and SrS:Eu, Sm were studied by the time dependence of their afterglow and the fluorescence rising process at the beginning of excitation. The numbers of traps in both phosphors were compared and the singly doped SrS:Eu was found to have approximately the same trap number as the latter at the absence of Sm inos. The absorption spectra of SrS:Eu,Sm at excited and bleached states were measured respectively. The difference at infrared region between them demonstrates the transitions of electrons from the traps to conduction band, which were studied by stimulated spectrum normally. The concentration dependence of Eu and Sm of this difference that we named stimulating absorption spectrum was examined. The results show that the complexes formed by combination of Sm ions and crystal defects such as anion impurity ions or vacancies act as the storageable traps, i.e.,Sm ions play a role of deepening the trap levels so that the trapped electrons can be stored stably.