Effect of Aluminum Doping on Zinc Oxide Thin Film Properties Synthesis by Spin Coating Method

A sol-gel spin coating method has been successfully used to synthesize pure zinc oxide (ZnO) and Al-doped ZnO thin films. Synthesis of pure phase of ZnO thin films with polycrystalline hexagonal wurtzite structure with the lattice parameters a=3.2568A and c=5.2108A have been revealed using XRD analysis. There is no change in the phase structure with Al doped ZnO thin films and the lattice parameters decreased with increased in Al-doping concentration. The crystallite size, lattice constants and strain are decreased, as the Al dopant concentration increases in ZnO lattice which is attributed to the interstitial substitution of Al ions in Zn sites into ZnO lattice as confirmed by EDX results. SEM studies show that with Al-doping the growth of the films takes place to be nanowire in structure at Al concentration up to 3% wt and the size reduced more at 5% wt. This indicates that Al-doping has an influence on the surface morphology of the films. Bandgap energy of ZnO is 3.37 eV with direct band to band transitions and decreased to 3.25 eV with increased Al-doping concentration. These properties of Al doped ZnO thin films make it a promising materials to be effectively used in many optoelectronic devices and application such as solar cell,  photocatalysis, gas sensor and so on.