The effect of Al on structure, morphology and optical properties of network texture ZnO thin films synthesized using the sol–gel method

Abstract

Aluminum (Al) doped zinc oxide (AZO) polycrystalline thin films with Al incorporation of 0–20at.% were deposited through the sol–gel dip coating technique. The important role of Al incorporation level in the microstructure evolution was determined using X-ray diffractometer, atomic force microscopy (AFM) and scanning electron microscopy (SEM). The XRD patterns confirmed that the hexagonal wurtzite type polycrystalline structure of the films and the incorporation of Al lead to substantial changes in the structural characteristics of ZnO films. The oriented structures of ZnO wrinkle network arrays are formed at a high Al level. The transmittance spectra were recorded by UV–vis spectrophotometer. Optical characterizations have revealed that the band gap energy of AZO films can be tuned between 3.23eV and 3.30eV as the Al concentration is varied from 0 to 20at.%. Four-point probe (FPP) method has been used to determine the electrical resistivity values of the films. The best sample with a resistivity of 3.2×10−4Ωcm and a transmittance of about 80% in visible region was achieved for the undoped film.