Effect of yttrium doping on structural and optical properties of zinc sulfide nanoparticles

Present work deals with the effect of Yttrium (Y) doping on the structural and optical properties of Zinc Sulfide (ZnS) nanoparticles synthesized by chemical co-precipitation method. The incorporation of Y in ZnS structure and the resulting elemental composition were confirmed using EDAX analysis. The SEM and HR-TEM images depicted the formation of ZnS agglomerates with narrow size distribution. Using XRD spectra it was analyzed that with increase in concentration of Y atoms, the crystallinity of ZnS lattice structure decreases, a significant deviation in the lattice structure was observed at 15 wt% Y doping. Raman analysis showed a monotonic decrease in vibration frequency of ZnS lattice with the incorporation of bulky Y ions. A decrease in the band gap from 3.97 to 3.75 eV was also observed with increase in Y doping upto 15 wt%. The photoluminescence spectra depicted that Y doping has a strong effect on the emission properties of the ZnS nanoparticles. Initially, it enhances the band edge emission by occupying the Zn vacancies in the lattice structure but at higher doping levels their tendency to move into the interstitial sites suppresses back the band edge emission. The blue emission from S vacancies is also observed to increase with Y doping.