The Effect of ${\hbox {Ca}}^{2+}$ Codoping on Shallow Traps in YSO:Ce Scintillators

Low temperature ($\sim$ 35 K) measurements of the scintillation kinetics of ${\rm Y}_{2}{\hbox {SiO}}_{5}:{\rm Ce}$ (YSO:Ce) have previously illustrated that shallow electron traps can play an important role in the scintillation mechanism. In addition, divalent calcium co-doping of isostructural ${\hbox {Lu}}_{2}{\hbox {SiO}}_{5}:{\rm Ce}$ (LSO:Ce) has been shown to eliminate shallow electron traps and decrease scintillation decay time while maintaining high light output. Here we investigate the effect of ${\hbox {Ca}}^{2+}$ codoping on the trap populations and scintillation kinetics of YSO:Ce. Single crystals were grown with ${\hbox {Ca}}^{2+}$ concentrations up to 0.5 at% relative to Y. Thermoluminescence measurements indicate a significant reduction in shallow traps, and a marked change in the scintillation kinetics can be seen in the scintillation time profiles as a result of ${\hbox {Ca}}^{2+}$ codoping.