Influence of Al, Ta Doped ZnO Seed Layer on the Structure, Morphology and Optical Properties of ZnO Nanorods

Background: Zinc oxide (ZnO) is one of the most attractive II-VI semiconductor oxide material, because of its direct wide band gap (3.37 eV) and large binding energy (60 meV). Zinc oxide (ZnO) is a promising semiconductor due to its optimised optical properties. Among semiconductor nanostructures, the vertically aligned one-dimensional ZnO nanorods are very important for nano device application. Methods: Vertically aligned ZnO nanorod arrays were grown on ZnO, aluminum doped ZnO (ZnO:Al), tantalum doped ZnO (ZnO:Ta) and aluminum and tantalum co-doped ZnO (ZnO:Al,Ta) seed layer by hydrothermal method. Results: The X-Ray Diffraction (XRD) investigation indicated the presence of hexagonal phase for the both seed layers and nanorods. The Scanning Electron Microscope (SEM) images of ZnO and doped ZnO seed layer thin-films show spherical shaped nanograins organized into wave like morphology. The optical absorption spectra revealed shift in absorption edge towards the shorter wavelength (blue shifted) for ZnO nanorods grown on ZnO:Al, ZnO:Ta and ZnO:Al,Ta seed layer compared to ZnO nanorods grown on ZnO seed layer. Conclusion: The increase in band gap value for the ZnO nanorods grown on doped ZnO seed layers due to the decrease in crystallite size and lattice constant as evidenced from XRD analysis. The unique property of Al, Ta doped ZnO can be used to fabricate nano-optoelectronic devices and photovoltaic devices, due to their improved optical properties.