Structural and optical properties of Cd1-xZnxS (0 ≤ x ≤ 0.3) nanoparticles

Cd1-xZnxS nanoparticles for Zn = 0-30 % were successfully synthesized by a conventional chemical co-precipitation method at room temperature. X-ray diffraction spectra confirmed the pure zinc blend cubic structure of undoped CdS; but Zn-doping on Cd-S matrix induced the mixed phases of cubic and hexagonal structure. The reduced crystal size, d-value, cell parameters and higher micro-strain at lower Zn concentration were due to the distortion produced by Zn2+ in Cd-S lattice. The enhancing diffraction intensity at lower Zn concentrations was due to the substitution of Zn2+ ions instead of Cd2+ ions whereas the reduced intensity after 20 % was due to the presence of Zn2+ ions both as substitutionally and interstitially in Cd-S lattice. The nominal stoichiometry and chemical purity was confirmed by energy dispersive X-ray analysis. The initial blue shift of energy gap from undoped CdS (3.75 eV) to Zn = 10 % (3.82 eV) was due to the size effect and also the incorporation of Zn2+ in the Cd-S lattice. The observed red shift of energy gap at higher Zn concentrations could be attributed to the improved crystallinity. The band gap tailoring was useful to design a suitable window material in fabrication for solar cells and other opto-electronic devices. The characteristic IR peaks around 617-619 cm-1 and the reduced intensity by Zn-doping confirmed the presence of Zn in Cd-S lattice. © 2014 Springer Science+Business Media New York.