Influences of Co doping on the structural, optical and magnetic properties of ZnO nanorods synthesized by hydrothermal route

Pure and Co-doped ZnO nanorods have been synthesized by a hydrothermal process. The structure, morphology and properties of as-prepared samples have been studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectrometer as well as by superconducting quantum interference device (SQUID). The structure and morphology analyses show that Co doping can slightly impede the ZnO crystallinity, influence the nanorods morphology, but cannot change the preferred growth orientation of ZnO nanorods. The amount of Co doping contents is about 3.0 at% in ZnO nanorods and dopant Co2+ ions substitute Zn2+ ions sites in ZnO nanocrystal without forming any secondary phase. The optical measurements show that the Co doping can effectively tune energy band structure and enrich surface states in both UV and VL regions, which lead to novel PL properties of ZnO nanorods. In addition, ferromagnetic ordering of the as-synthesized Zn1−xCoxO nanorod arrays has been observed at room temperature, which should be ascribed to sp–d and d–d carrier exchange interactions and presence of abundant defects and oxygen vacancies.

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