Effect of Mg2+ co-doping on the photo- and thermally stimulated luminescence of the (Lu,Gd)3(Ga,Al)5O12:Ce epitaxial films

Abstract

Photoluminescence and thermally stimulated luminescence of Ce3+ - doped (Lu,Gd)3(Ga,Al)5O12 epitaxial films co-doped with different concentrations of Mg2+ ions (varying from 0 to 0.09 at.%) are investigated in the 60–500 K temperature range under selective photoexcitation in the Ce3+ - related 4f → 5d2 and 4f → 5d1 absorption bands and in the absorption bands arising from the 8S7/2→6IJ and 8S7/2→6PJ electronic transitions of Gd3+ ions. Influence of Mg2+ ions on the Ce3+ - related photoluminescence intensity, spectrum, decay kinetics, temperature dependence of the emission intensity, and the activation energy of the luminescence thermal quenching is studied. The shortening of the luminescence decay time and simultaneous reduction of its light yield are explained by the presence of {Ce3+ - Mg2+} centers in the Mg2+ - containing films, where the luminescence optical quenching occurs in the 5d1 excited state of Ce3+ in these centers. Co-doping with Mg2+ results in the reduction of the afterglow and thermally stimulated luminescence and shortening of the afterglow decay kinetics. It influences also defects creation spectra and the activation energy of the photostimulated defects creation. The optimum Mg2+ content in the (Lu,Gd)3(Ga,Al)5O12:Ce epitaxial films is estimated to be around 0.005 at.%.