Consequence of Cobalt Incorporation on Structural and Optical Properties of Transparent Nano-Crystalline ZnO Thin Film

Abstract

We have investigated the effect of Co(4%) doping on structural and optical properties of the zinc oxides thin film deposited on glass substrate by spin coating techniques. The structural analysis and surface morphology have been carried out with the help of XRD and Atomic Force Microscopy (AFM) characterisation respectively. UV-Vis spectroscopy and Photoluminescence spectroscopy has been employed to obtain information about absorption and luminescence properties of Pure and Co-doped ZnO thin film. The XRD patterns confirm the crystalline nature and hexagonal wurtzite structure formation in the samples. The thickness of the film is measured by MProbe Thin Film Measurement System. AFM observations indicate a smooth surface morphology with small grains. AFM results suggest that cobalt doping decreases the average grain size and roughness of ZnO thin film. UV-Vis analysis indicates that absorption edge of cobalt doped ZnO thin film lie in the visible region and energy band gap of Zn0.96Co0.04O (3.05eV) is less than pure ZnO thin film (3.2eV). The defect generated absorption in the visible region is present due to the incorporation of cobalt in ZnO thin film. Photoluminescence study shows the broad emission in the visible region in all samples. The Co
doping causes an increase in broad emission in the visible region.