Study on the mechanism of afterglow in CsI: Tl and the afterglow suppression in CsI: Tl, Eu

Although there are many new scintillators being developed recently, CsI: Tl is still a very efficient one among them. However it suffers from afterglow which limits application in high-speed x-ray imaging. In order to find out the mechanism of afterglow and the method to suppress afterglow in CsI: Tl, the theoretical model of perfect CsI, CsI: Tl and CsI: Tl, Eu are built by the software Material Studio. The total and partial density of states of these three models is calculated within the framework of generalized gradient approximation and ultra-soft pseudo-potential. The results indicate that the generation of afterglow in CsI: Tl is due to the impurity energy bands introduced by Tl. Moreover, co-doping CsI: Tl with Eu will introduce deeper impurity energy bands which can effectively scavenge the electrons trapped by the shallow impurity energy bands introduced by Tl, thus suppressing the afterglow in CsI: Tl. (author)