Optically stimulated persistent luminescence of europium-doped LaAlO3 nanocrystals

Abstract

Optically stimulated persistent luminescence was investigated for europium-doped LaAlO₃ nanocrystals. This system shows conventional luminescence of both the Eu³⁺ line emission and the weak broad-band emission of Eu²⁺ upon UV excitation. The persistent luminescence is predominantly associated with the Eu³⁺ emission, and can be amplified significantly through irradiation with IR at 975 nm. The conventional luminescence from Eu³⁺ is strongly enhanced when the material is excited simultaneously with both UV and IR radiation. The enhancement of persistent luminescence is accompanied by increased persistent photoconductivity. The charge transfer band of the LaAlO₃:Eu³⁺ nanocrystals in the UV excitation spectra significantly weakens with increasing IR excitation power, also correlating well with the enhancement of persistent luminescence. Finally, a mechanism is presented for the optically stimulated and persistent luminescence in this Eu²⁺- and Eu³⁺-doped LaAlO₃ material.