Structural characterization of luminescent Ca0.95Cd0.05S

Abstract

Cadmium-doped calcium sulphide has great potential as a broadband light source in both powder and thin film electroluminescent devices. We now report the first structural investigation of polycrystalline cadmium-doped calcium sulphide using a combination of transmission electron microscopy (TEM) with microanalysis, and X-ray diffraction. We show that the crystals formed by direct reaction of CaS and CdS under excess sulphur do not yield an even distribution of cadmium. We also show that the crystals are heavily dislocated with defect structures typical of rock-salt structures. We show that TEM can be successfully applied to the study of these moisture-sensitive materials without the formation of artefacts and that TEM should be a valuable tool for studying their thin film structures.