Time-resolved spectroscopy of exciton states in single crystals and single crystalline films of YAlO3 and YAlO3?:?Ce.

Luminescence characteristics of single crystals (SC) and single crystalline films (SCF) of YAlO3 and YAlO3 : Ce are studied at 4.2-300 K under photoexcitation in the 4-20 eV energy range. The origin and structure of the intrinsic and impurity defects responsible for various exciton-related emission and excitation bands are identified. The [?]5.6 eV emission of YAlO3 SCF is ascribed to the self-trapped excitons. In YAlO3 SC, the dominating 5.63 eV and 4.12 eV emissions are ascribed to the excitons localized at the isolated antisite defect {\rm Y}_{{\rm Al}}^{3+} and at the {\rm Y}_{{\rm Al}}^{3+} defect associated with the nearest-neighbouring oxygen vacancy, respectively. The thermally stimulated release of the electrons, trapped at these defects, takes place around 200 K and 280 K, respectively. The presence of {\rm Y}_{{\rm Al}}^{3+} -related defects and isolated oxygen vacancies (AlO5 units) in YAlO3 SC is confirmed by NMR measurements. The formation energies of various {\rm Y}_{{\rm Al}}^{3+} -related defects are calculated within the density functional theory. The influence of various intrinsic and impurity defects on the luminescence characteristics of Ce3+ centres is clarified. [ABSTRACT FROM AUTHOR]