Swift heavy ion induced structural modification and photo-luminescence in CaS:Bi nanophosphors

CaS:Bi nanocrystalline powder of average grain size 35 nm was prepared by wet chemical co-precipitation method and irradiated with 100 MeV oxygen ions at fluences between 1×10¹² and 1×10¹³ ion/cm². The irradiation induced damage and modifications were studied using X-ray Diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. With the increase in ion fluences, the crystallinity of CaS was destroyed upto 25.9 % for the reflection (200) and 21.1 % for the reflection (220) and the peaks broadens at a much faster rate due to grain breaking process. Structural parameters such as grain size, strain and dislocation density have shown a significant change after ion irradiation. The effects of different dopant concentrations on PL emission intensity after irradiation were also investigated. A blue shift of the photoluminescence peak with increasing ion fluence was noticed and was also ascribed to a decrease in the CaS grain size.