Synthesis, structure and optical properties of (Mn/Cu) co-doped ZnO nanoparticles

Mn/Cu co-doped ZnO (Zn_0.99-xMn_xCu_0.01O) nanoparticles were synthesized by the solid state reaction method to investigate the relationship between the band gap and the refractive index. The stoichiometry was provided by increasing x values (x = 0.00, 0.01, 0.02, 0.03, 0.04, and 0.05). The X-ray diffraction (XRD) method was utilized for the structural analysis of all Mn/Cu co-doped ZnO nanoparticles. Hexagonal Wurtzite structure was established by making use of the c/a ratios of the ZnMnCuO nanoparticles. Photoluminescence (PL) properties were measured by employing the Agilent Cary Eclipse Fluorescence Spectrophotometer to discover the structural defects. The red emission with its wavelength within the range of 620–750 nm was observed. The red emission centered at 700 nm could be attributed to oxygen vacancy (V_o) which was strongly dependent on the Mn concentration. The Fourier Transform Infra-Red (FT-IR) spectra (4000 - 400 cm⁻¹) of the samples were recorded in the By PerkinElmer Spectrum Two FTIR-ATR spectrophotometer. Scanning Electron Microscope (SEM) technique was applied to determine the surface morphology, crystallite size, and the shapes of the nanoparticles. The elemental compositions of the nanoparticles were obtained by Electron Dispersive Spectroscopy (EDAX). The optical properties of the nanoparticles were obtained by using the Shimadzu 2600 Ultraviolet–Visible (UV-VIS) Spectrophotometer. The energy band gaps of the samples were calculated and the effects of dopant elements on optical properties were discussed. The refractive index was calculated by using the five different models. The maximum band gap occurred for Zn_0.97Mn_0.02Cu_0.01O with a band gap energy of E_g = 3.28 eV.