Untersuchungen über Elektronenhaftstellen in ZnS-Phosphoren

Glow curves of different ZnS phosphors were measured and analysed in the temperature region from 4.2 °K to 500 °K. It was attempted to clarify the origin of the glowpeaks observed above 77.4 °K and to attribute them to structural defects in the ZnS lattice. In glow curves started at 4.2 °K a strong dependence of the trap distribution on the method of preparation of phosphors was observed. In particular a ZnS(Cu) phosphor containing oxygen shows a broad continuum of shallow traps between 4.2 °K and 150 °K. In a ZnS(Cu, Ga) phosphor free of oxygen the trap density of the continuum of shallow traps is very small. Moreover this phosphor shows a sharp glowpeak at about 60 °K. The afterglow at the excitation temperatures of 4.2 °K and 77.4 °K was also studied. It is concluded that the rapid amptying of shallow and, to a lesser extent, of deep traps should be due to a tunneling process leading to luminous recombination of the trapped electrons with the activator levels.