Determination of the position of the 5d excited levels of Ce3+ ions with respect to the conduction band in the epitaxial films of the multicomponent (Lu,Gd)3(Ga,Al)5O12:Ce garnets

Abstract

Temperature dependences of the intensity and decay kinetics of the Ce3+ - related photoluminescence and characteristics of thermally stimulated luminescence are investigated in the 77–500 K temperature range for the epitaxial films of the multicomponent garnets of the type of Lu3−xGdxGayAl5−yO12:Ce with Ce content of 0.3–0.7 at. %, where x varies from 0.14 to 3 and y varies from 0 to 3.54. Different methods are used for the determination of energy distances between the excited 5d1 and 5d2 levels of Ce3+ ions and the conduction band (CB) and their applicability is compared. The dependences of the 5d1,2 – CB energy distances on the multicomponent garnet composition are clarified. The 5d1 – CB energy distance is found to decrease by about an order of magnitude with the increasing Ga3+ content. The most drastic decrease, observed at the Ga3+ content around y ≈ 1.7, is suggested to arise from the change in the Ga3+ position from the smaller tetrahedral to larger octahedral Al3+ sites. This effect is explained by the lattice distortion due to the substitution of smaller Lu3+ and Al3+ ions by larger Gd3+ and Ga3+ ions. Application potential of these epitaxial films for fast 2D-imaging is discussed.