Synthesis and characterization of Sn-doped CdZnS nanoparticles

Tin (Sn)-doped cadmium zinc sulphide nanoparticles (CdZnS : Sn) were synthesized by the chemical bath deposition method with two different concentrations of Sn (2 and 4 mol%). X-ray diffraction (XRD) pattern reveals the formation of CdZnS nanoparticles with cubic and hexagonal structure. It was observed that the presence of Sn does not alter the structure of CdZnS. Average crystallite size was measured from XRD data by using Scherrer's formula. From the study of absorption spectra, band-to-band absorption was obtained at 460 and 490 nm, respectively, for the Sn-doped (2 and 4 mol%) CdZnS nanoparticles. Energy bandgap for undoped and Sn-doped CdZnS varies from 3.5 to 2.9 eV with error +/- 0.05 eV. The presence of Sn was confirmed by energy-dispersive X-ray analysis. The effect of dopant concentration on the photoluminescence (PL) intensity has also been studied. The PL emission peak has been observed at 540, 550 and 560 nm for the Sn-doped (CdZnS, CdZnS 2 mol% and CdZnS 4 mol%), respectively, nanoparticles. XRD and PL analyses demonstrate that the Sn2+ ions uniformly substitute Cd2+ sites or interstitial sites in CdZnS lattice, which influence the optical properties. Increase in the concentration of Sn shifts the UV-vis absorption spectra and PL emission spectra towards higher wavelength side. Particle size and the crystallinity of CdZnS : Sn nanoparticles were confirmed through atomic force microscopy.