STUDY ON PHOTOLUMINESCENCE PROPERTIES OF Co-DOPED ZnO

ZnO and Co-doped ZnO have been synthesized by co-precipitation technique. X-ray diffraction (XRD) patterns and absorption spectra show that Co ions are doped into the lattice positions of ZnO. Photoluminescence (PL) experiments on the samples have been performed in order to study the sp-d interaction in ZnO: Co. Room temperature measurements show two additional emissions related to Co besides the ZnO exciton-related and trap emissions. The two emissions are attributed to the transitions from Co+ to the excited Co2+ state and from E-2(G) to (4)A(2)(F), respectively. The charge-transfer transitions related to Co2+ exciting 3d intrashell luminescence at 1.78 eV has been observed. A blue-shift in the exciton-related emission, a red-shift in the blue emission and no shift in the green emission were revealed and interpreted by the sp-d interaction.