Structure, morphology and optical properties of undoped and MN-doped ZnO_(1-x)S_x nano-powders prepared by precipitation method

The undoped and Mn-doped ZnO_(1-x)S_x nano-powders were successfully synthesized by precipitation method without using any capping agent. Its structure, morphology, elemental analysis, optical and luminescence properties were determined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), UV-vis spectroscopy (UV) and photoluminescence spectroscopy (PL). A typical SEM image of the un-doped ZnO_(1-x)S_x nanoparticles exhibit flake like structures that changes to nearly spherical particles with Mn-doping. The XRD of undoped and Mn doped ZnO_(1-x)S_x pattern reveals the formation of a product indexed to the hexagonal wurtzite phase of ZnS. The nanopowders have crystallite sizes estimated from XRD measurements were in the range of 10-20 nm. All the samples showed absorption maximum of ZnO_(1-x)S_x at 271 nm and high transmittance in UV and visible region, respectively. The undoped ZnO_(1-x)S_x nanoparticles show strong room-temperature photoluminescence with four emission bands centering at 338 nm, 384 nm, 448 nm and 705 nm that may originate to the impurity of ZnO_(1-x)S_x, existence of oxide related defects. The calculated bandgap of the nanocrystalline ZnO_(1-x)S_x showed a blue-shift with respect to the Mn-doping. The PL spectra of the Mn-doped samples exhibit a strong orange emission at around 594 nm attributed to the ⁴T₁-⁶A₁ transition of the Mn²⁺ ions.