Zur Temperaturabhängigkeit der Elektrolumineszenz von Zinksulfid-Phosphoren

Abstract

The temperature dependence of brightness waves and of average emission intensity of ZnS powder phosphors excited by square pulses was studied. In certain temperature ranges brightness waves with two peaks in each half-period of the exciting field are observed. Microscopical investigations of individual luminescent areas of a ZnS-grain showed the second peak in the brightness wave to be present in that half-period which in the model of delayed recombination is called the excitation half-period. It is shown that this emission takes place after the excitation process (duration <2μs) is finished and the resulting field in the inner parts of the crystallites has almost faded. Because of this fact and on the basis of glow and built-up investigations in the excitation half-period a spontaneous recombination of electrons thermally released from traps is proposed. Therefore the brightness waves with two peaks, but also emission in the excitation half-period is observed for temperatures at which — in the time average — many traps are still filled but on the other hand the probability for their emptying is already considerable.