Time-resolved spectroscopy of exciton states in single crystals, single crystalline films and powders of YAlO_3 and YAlO_3:Ce

TL;DR

This study investigates the luminescence properties and defect structures of YAlO_3 and YAlO_3:Ce in various forms, revealing the origins of exciton emissions and defect-related luminescence across a temperature range.

Contribution

It provides a detailed analysis of defect-related exciton emissions and their origins in YAlO_3 and YAlO_3:Ce, including identification of specific defect structures and their effects on luminescence.

Findings

Self-trapped exciton emission at ~5.6 eV in YAlO_3 SCF.

Exciton emissions at 5.63 eV and 4.12 eV linked to antisite defects and oxygen vacancies.

Thermally stimulated electron release at 200 K and 280 K.

Abstract

Luminescence characteristics of single crystals (SC), single crystalline films (SCF), powders and ceramics of YAlO_3 and YAlO_3:Ce have been studied at 4.2-300 K under photoexcitation in the 4-20 eV energy range and X-ray excitation. The origin and structure of defects responsible for various exciton-related emission and excitation bands have been identified. The ~5.6 eV emission of YAlO_3 SCF is ascribed to the self-trapped excitons. In YAlO_3 SC, the dominating 5.63 eV and 4.12 eV emissions are ascribed to the excitons localized at the isolated antisite defect Y^{3+}_Al and at the Y^{3+}_{Al} defect associated with the nearest-neighbouring oxygen vacancy, respectively. Thermally stimulated release of electrons, trapped at these defects, takes place at 200 K and 280 K, respectively. The formation energies of various Y^{3+}_{Al}-related defects are calculated. The presence of Y_{Al} antisite-related defects is confirmed by NMR measurements. The influence of various intrinsic and impurity defects on the luminescence characteristics of Ce^{3+} centers is clarified.