Study of charge carrier trapping by EPR and TSL methods in ZnxMg1-xWO4 single crystals

Abstract Charge carrier trapping was studied using EPR and TSL methods in ZnWO4, MgWO4 and mixed ZnxMg1-xWO4 crystals. An electron trapped at a perturbed W site was detected in MgWO4. It was also shown that holes are trapped at oxygen ions thus forming O− centers. Two different O− centers, one perturbed by a cation vacancy, another by Al impurity, were found in MgWO4, while a single hole center perturbed by Cd impurity and hydroxyl group nearby was detected in ZnWO4. The number of non-equivalent hole centers increases up to five for the mixed crystals due to the perturbations induced by statistically distributed substitutional cations. It is shown that the thermal release of holes is accompanied by thermostimulated luminescence (TSL). The broadening of the TSL peaks typically observed in mixed crystals is connected with the increase of the number of non-equivalent trapping centers of the same type.