SYNTHESIS AND CHARACTERIZATION OF STRUCTURAL AND OPTICAL PROPERTIES OF NI-DOPED ZINC SULFIDE NANOPARTICLES

Abstract

The band-gaps of wide band gap metal sulfide semiconductors such as ZnS, are significantly reduced when doped with transition metal ions Ni2+.The new composite materials offer promising and versatile applications in spintronic devices, solar cells and other optoelectronic devices, and in photonics etc. It has led to substantial modifications in methods of synthesis for ZnS nanoparticles. In this research work, we have synthesized ZnS nanoparticles via simple chemical precipitation method. ZnS nanoparticles have been characterized using UV-visible spectra and Raman spectroscopy. For morphological studies we have used scanning electron microscopy (SEM). The optical band gap has been evaluated from UV-vis-nir absorption spectrum of the particles. Raman spectroscopy is used to study the rotational, vibrational and other modes of the sample, as we are interested to reveal properties of nanoclusters treating as those as nano-molecules. We correlate the variations in properties with their structures. Our investigations confirm formation of large single crystals (nanomolecules) yielding resonant Raman peaks. It is further confirmed from SEM images of the samples. Nanoparticles have special properties other than bulk. Their surface energy contributions are entirely different from their bulk counterparts and play dominant role in its stability. Thus, we assign a special phase for them as “Nanophase”. The phenomenon of nano-cluster (aggregates) formation of nickel atoms via nucleation is also confirmed for high doping concentrations of nickel, which results into inverse trend for band-gap.