Optical, structural, electrical and photocatalytic properties of aluminum doped zinc oxide nanostructures

Abstract

The Al-doped ZnO (Zn1-xAlxO, x = 0.00, 0.02, 0.04, 0.06, and 0.08) nanostructures were synthesized by the chemical vapor deposition technique. Analysis by X-ray diffraction reveals that both undoped and Al-doped ZnO nanostructures are crystallized in a single-phase wurtzite structure with a preferred orientation along the (101) plane. The addition of Al was studied to see how it influenced bond length, crystallite size, unit cell volume, lattice strain, and dislocation density. Field-emission scanning electron microscope imaging showed a significant variation in the morphology with increasing the Al doping level. Absorption spectra in the UV–Visible range revealed that introducing Al3+ ions into the ZnO lattice causes a blue shift in the optical band gap, which was explained according to Burstein-Moss effect and variation of the electronic structure. The direct electrical conductivity measurement showed a transformation between two conduction mechanisms upon variation of the temperature. Transition of the charge carriers from shallow and deep donor levels dominated in the low and high temperature ranges, respectively. The photodegradation rate constants and degradation efficiency were determined as well as the photocatalytic mechanism was described. Upon reaching the x = 0.08 Al doping level, the photocatalytic efficiency of the examined samples increased by 1.7-fold. The obtained results demonstrate that Al doping can tune the electrical, optical, and photocatalytic properties of ZnO nanostructures that make them applicable for many optoelectronic applications.