Structural and optical properties of cobalt doped ZnO nanocrystals

Zn _1-xCo _xO nanocrystals with nominal Co doping concentrations of x = 0-0.1 were synthesized through a simple solution route followed by a calcining process. The doping effects on the structural, morphological and optical properties were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman, absorption and luminescence spectroscopy. The results indicated that a small amount of Co ions were incorporated into ZnO lattice structure, whereas the secondary phase of Co ₃O ₄ was segregated and precipitated at high Co doping concentrations, the solid solubility of Co ions in ZnO nanocrystals could be lower than 0.05. The spectra related to transitions within the tetrahedral Co ²⁺ ions in the ZnO host crystal were observed in absorption and luminescence spectra.