Structural, optical and morphological properties of Mn:Cu co-doped ZnS films

Abstract

Stoichiometric films of zinc sulfide (ZnS) were grown on quartz substrate using a wet chemical technique, both without and in the presence of copper (Cu) and manganese (Mn) dopants. The structural, morphological and luminescence properties of the as-deposited films were investigated using X-ray diffraction, atomic force microscopy, optical and luminescence spectroscopy. The sample compositions were analyzed using atomic absorption spectroscopy. It was found that changes in stoichiometry had a negligible effect on the crystalline phase and optical properties of the films, whereas variations in dopant concentration significantly altered their surface morphology and luminescence properties. The absorption edge of ZnS, determined using absorption spectroscopy was found to be blue-shifted from its bulk counterpart due to the confinement effect. The photoluminescence (PL) properties of the undoped and Mn:Cu co-doped ZnS samples have been studied in detail. The PL spectra of undoped samples consisted of a broad asymmetric peak which, upon deconvolution, was correlated with band edge transition and radiative recombination via intrinsic defect states. In contrast, doped samples showed intense Gaussian peaks positioned differently from the undoped samples, indicating the substitution of dopants at the zinc site in the ZnS lattice. The peak intensity also varied with changes in doping percentages in the samples. In this study, a high luminescence yield was achieved even at very low dopant concentrations.