Structural and optical properties of cobalt doped ZnO nanocrystals

Zn1−xCoxO 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 Co3O4 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 Co2+ ions in the ZnO host crystal were observed in absorption and luminescence spectra.

► Zn1−xCoxO nanocrystals were synthesized through a simple solution route.
► Small amounts of Co2+ ions were incorporated into ZnO lattice.
► The average diameter of particles decreases with Co concentration increasing.
► The defect emissions of ZnO nanocrystals were modified by Co doping.
► The energy transitions related to Co2+ are observed in absorption and PL spectra.