Structural, Optical and Magnetic Properties of Cu-Doped ZnO Nanoparticles by Co-Precipitation Method

Zn_{1− x} Cu _x O (0 ≤ x ≤ 0.2) nanoparticles were prepared by co-precipitation method followed by drying at 200 °C. A non-ionic surfactant Tween-80 which was not reported in earlier studies, was used during preparation process. X-ray diffraction analysis showed the formation of wurtzite ZnO phase nanostructures. The Rietveld analysis showed the appearance of impurity phase (CuO), when Cu²⁺ was doped with ZnO (x = 0.05 to 0.2). Morphological observations using scanning electron microscopy show the formation of nanoparticles with remarkable morphologies. Photoluminescence spectra revealed emission bands in both UV and visible regions due to the defect centres acting as trap levels. Diffuse reflectance spectroscopy (DRS) showed a decreasing trend in the value of the band gap with increasing Cu²⁺ doping for lower concentration (x = 0 to 0.1) and then increasing trend for higher concentration of Cu²⁺ doping. (x = 0.1 to 0.2). The elemental composition of Zn, Cu and O was quantitatively obtained from EDAX analysis where the chemical composition was close to the starting stoichiometries. Magnetisation-Field (M-H) hysteresis curves revealed the appearance of ferromagnetic behaviour, where the magnetic characteristics such as coercivity and saturation magnetization values, were found to be sensitive to Cu²⁺ doping level.