Zn0.91Cu0.04M0.05O (M=Ni, Co, Cr) nanocrystals: Structural study and energy gap tailoring

Abstract Zn 0.91 Cu 0.04 M 0.05 O (M=Ni, Co, Cr) nanocrystals were successfully synthesized by co-precipitation method and the structural and optical properties have been investigated. X-ray diffraction spectra showed that the hexagonal wurtzite structure was not altered by TM co-doping. Due to the less solubility of Ni in Zn–O, the NiO phase was emerged in Ni, Cu co-doped ZnO nanocrystals. The change in lattice parameters was discussed corresponding to the radii of doping element. The surface morphology of TM co-doped ZnO nanocrystals was studied by scanning electron microscope and the presence of compositional elements such as Ni/Co/Cr, Cu and Zn with their nominal stoichiometry was confirmed by energy dispersive X-ray spectra. The shift in band gap by TM-doping was discussed based on the strength of the sp–d spin-exchange interactions between the band electrons and localized d-electron of the TM dopant.