Tailoring properties of Cu-doped ZnO nanoparticles

Abstract Using the sol-gel process, zinc oxide nanoparticles doped with copper at different concentrations x = 0, 5, 10, and 15 wt % were synthesized, and their optical, structural, and luminous characteristics were thoroughly examined. The hexagonal wurtzite structure was preserved in the Cu-doped ZnO samples, according to the X-ray diffraction analyses. The lattice parameters for pure ZnO are a = b = 3.237 Å and c = 5.182 Å. Cu-doping causes minor lattice changes. According to the deformation of the ZnO lattice caused by Cu-doping, the crystallite size decreased from 47.54 nm for pure ZnO to 21.27 nm for 15 wt % Cu-doped ZnO. Due to oxygen vacancy defects and Cu-related defect states, Cu-doped ZnO showed increased green (540 nm) and blue (435 nm) emissions in PL spectra, whereas greater doping concentrations resulted in a decrease in near-band-edge ultraviolet (UV) emission at 380 nm. It was demonstrated that Cu-induced states were contributing to the ZnO band gap by diffuse reflectance spectroscopy (DRS), which showed a shift in the optical band gap from 3.23 eV for pure ZnO to 3.69 eV with 5 wt % Cu-doping and then a minor reduction to 3.61 eV with 15 wt % Cu-doping. Raman investigation revealed distinctive peaks at 99 cm −1 (E 2L ), 437 cm −1 (E 2H ), and 5 84 cm −1 (E 1 (LO)) in both pure and Cu-doped ZnO. As the concentration of Cu increased, the Eı(LO) mode widened and changed to a lower wavenumber, indicating a rise in the quantity of oxygen vacancies.