Cathodoluminescence of Powder Layers of Nanometer-Sized Y2O3:Eu and Micrometer-Sized ZnO:Zn Phosphor Particles

We present a simple method to measure the cathodoluminescence of charging and non-charging phosphor powder layers at low primary electron beam energy. The method is based on comparing a non-charging surface of a conducting material such as copper or indium tin oxide with charging surfaces of non-conducting phosphors. The phosphors that were investigated were ZnO:Zn, which is slightly conductive and supposed not to charge upon electron bombardment, and Y 2 O 3 :Eu, which charges at sufficiently high current density. It was found that the luminous efficacies of ZnO:Zn and Y 2 O 3 :Eu at 5 keV primary beam energy were 23 and 16 lm/w respectively, larger than reported in the literature. This is partly explained by calculating the efficacy from the summation of the luminances measured in the reflected and transmitted mode. This method also minimizes the inaccuracy introduced by the effect of the coating weight. The ratio between luminances measured in reflection and transmission is described in terms of a one-dimensional light scattering theory.