Trapping and luminescence mechanisms in manganese-doped zinc silicate phosphorsa tunneling model

Abstract

We have investigated electron trapping and luminescence (phosphorescence, thermoluminescence and photostimulated luminescence) mechanisms in Mn and Mn+As doped Zn2SiO4 phosphors. The intensities of both the phosphorescence and photostimulated luminescence are found to decay with time approximately as (time)-1. The generally accepted model of such a decay of phosphorescence, based on thermal release of electrons from a broad distribution of trap energy levels, cannot explain the observed decay of the photostimulated luminescence. In order to explain both results we have developed a new model based on radiative recombination by tunneling between holes trapped on Mn ions and electrons in shallow traps or in excited states of the deeper traps. We derive a simple expression which describes for both experiments at all times the decay of the light intensity and its dependence on experimental conditions. The agreement between theory and experiment is found to be excellent.