Structural, chemical and optical properties of Co-doped ZnO nanoparticles obtained from an aqueous method

Co-doped ZnO nanoparticles were obtained by aqueous synthesis with an annealing at 400 °C. The incorporation efficiency of Co into the ZnO lattice was found to be around 100%. The nanoparticles keep the wurzite phase in all the Co-doping range. However, the lattice parameters and strain change monotonously mainly up to about 1 at% Co doping. The luminescence, which was signed by a wide emission band that rises from 2.2 eV to 3.3 eV, reduces the intensity as the Co-doping increases. That behavior was related to the strong influence of Co after substituting Zn in any place of the lattice. Additionally, a different approach was made on the O 1s XPS peak at binding energy BE 531.5 eV. We associate this peak to O-O re-bond caused by inward relaxation due to Zn vacancy. Such consideration is valid for doped and non-doped ZnO.