Luminescence of Rare-Earth-Activated Zinc Sulfide

The line structure of the photoluminescence of ZnS:Tb, ZnS:Nd, ZnS:Tm, and ZnS:Dy has been studied under various preparative conditions. There is a strong tendency for rare-earth pairing with other lattice defects in the presence of excess S. This pairing is manifested by the appearance of new emission lines and excitation bands. Of the many distinct sites for the rare-earth ion, one seems to stand out as most important in electroluminescence, although it gives only a minor contribution to the photoluminescence. Using a variety of luminescent phenomena, we are able to count at least four distinct sites for trivalent rare-earth ions in ZnS, and there is strong evidence that more exist.