Long afterglow phosphorescent characteristics of BaAl2O4:Eu,Dy films

BaAl2O4:Eu,Dy (BAO) films have been fabricated on Si substrate by laser ablation, and their fundamental optical property and afterglow characteristics are discussed in comparison with the SrAl2O4:Eu,Dy (SAO) films. The intense green emission near 500 nm that originates from 5d to 4f transition in Eu2+ ions was clearly observed from the BAO films. This photoluminescence peak was at a shorter wavelength than that of the SAO films (λ = 520 nm). The afterglow intensity from the BAO films disappeared within a few minutes whereas that of the SAO films lasts over 20 min. The hole-trap depth (Et) created by Dy as the auxiliary activators, which strongly affects the afterglow characteristics, was estimated on the basis of the thermally stimulated luminescence (TSL) result. The TSL glow curve for BAO films showed two broad peaks at 320 K and 450 K. The calculated Et for each peak was 0.2 eV (for the 320 K peak) and 1.2 eV (for the 450 K peak). On the other hand, Et = 0.5 eV was obtained from the SAO films. The hole-trap depths of the BAO film are either too shallow or too deep to affect the afterglow characteristics at room temperature.