Synthesis and characterization of zinc oxide and al doped zinc oxide by sol-gel technique

Abstract

Nano-structured Zinc Oxide (ZnO) and Aluminum doped Zinc Oxide (AZO) thin films have been synthesized and their surface morphological, structural, optical and electrical properties together with the photo catalytic activity have been studied. The thin films were deposited on glass substrate by sol-gel dip coating technique with doping concentration of Al varied between 0 to 6 wt%. The scanning electron microscopy (SEM) images of the films showed uniform deposition together with the formation of nano-particles throughout the substrate. The particle size decreases with the incorporation of dopant and the size distribution become more uniform with the increasing amount of Al dopant. Structural characterizations reveal high crystallinity of the ZnO thin film possessing hexagonal wurtzite structure. Crystallinity of the film is found to be decreasing with the increasing concentration of Al dopant. The electrical conductivity of the thin film is found to be increased with the incorporation of Al content. The optical transmittance spectrum of the films showed a very good transmittance, of 81%, within the visible wavelength region for the undoped which decreases with the amount of Al dopant. The band gaps of the films are found to be varied with the amount of doping. The AZO thin films exhibited highly enhanced photo-catalytic activity comparing to pure ZnO thin films under UV illumination. The higher surface area of the thin film due to the smaller particle size distribution together with its lower band gap energy is responsible for the enhanced photo catalytic activity of AZO than that of pure ZnO films. The nano-crystalline AZO thin films with high optical transparency together with lower resistivity produced by sol gel dip coating technique would be a better choice for transparent electrode of optoelectronic devices and can be found application in water purification and environment cleaning process.