The carrier capture and recombination processes in Ln3+ -activated scintillators

The ability of activator ions to capture charge carriers and assume a different charge state under ionizing radiation is essential for efficient performance of rare-earth (RE)-doped scintillator materials utilizing the carrier recombination energy. In this paper the sequence of carrier trapping is discussed and interpreted using a simple, single-configuration-coordinate model for two different cases: In one case (LuP[O.sub.4]:Ce, YAl[O.sub.3]:Ce, LuAl[O.sub.3]:Ce) the charge state involved in the scintillation mechanism is [Ce.sup.4+], while in the other (LuP[O.sub.4]:Yb, YbP[O.sub.4]) it is Y[b.sup.2+]. The possibility of a nonradiative recombination via Ce and Yb ions is also considered and found highly unlikely in accordance with experimental results.