Tailoring of Optical and Physical Properties of ZnO Films by Co-Doping Concentration

Abstract

The modification and tailoring characteristic of nanostructured materials are of great interest due to controllable and unusual inherent properties in such materials. Cobalt-doped zinc oxide (Co:ZnO) thin films were prepared using the sol-gel technique with the spin coating method. The optical and physical properties of Co:ZnO films were tailored by the adjustment of Co concentration, which was realised by varying the ratio. The morphology and structure properties were characterised, and the effects of Co doping and post-annealing were investigated. Similar with undoped ZnO, the synthesised Co:ZnO films have a hexagonal wurtzite structure with the crystallinity deteriorated, and present high visible transparency with the absorption edge redshifted. Debye–Scherrer analysis of XRD pattern reveals an increase of the crystallite size with doping concentration. The bandgap, calculated using a Tauc Plot method, reveals a decrease in the absorption onset with an increase in the doping level.