Effect of Co doping on morphology, optical and magnetic properties of ZnO 1-D nanostructures

One-dimensional Co doped ZnO nanostructures have been successfully synthesized by a wet chemical technique. X-rays diffraction results reveal that with Co doping ZnO retained its wurtzite structure, but lattice constants are slightly decreased. SEM results demonstrate that Co doping changes morphology of ZnO nanostructures from nanowires to nanorods. It has been confirmed through HRTEM results that Co dopant cannot change preferred growth orientation of ZnO, although it remarkably influenced the grain size and morphology. The Co dopant is found to be uniformly distributed over various parts of single nanorod and settles at 2+ chemical oxidation state without forming any secondary phases. In response to Co doping, near band edge peak in UV region is red shifted and VL band peak intensity is remarkably enhanced. It is also found that Co doping induces large amount of defects in ZnO band structure. Furthermore, the doped nanorods exhibit ferromagnetic behavior at room temperature, which is attributed to the presence of abundant amount of defects and oxygen vacancies. The tunned band gap and ferromagnetic behavior at room temperature with high M _s and H _c values make them potential for spintronics applications.