Atmospheric pressure based electrostatic spray deposition of transparent conductive ZnO and Al-doped ZnO (AZO) thin films: Effects of Al doping and annealing treatment

Zinc oxide (ZnO) and Al-doped ZnO (AZO) thin films were prepared by electrostatic spray deposition method at atmospheric pressure followed by annealing. The effects of annealing and Al doping on the structural, electrical and optical properties of the films were investigated. The results show that films have random orientation with compact hexagonal wurtzite structure. It also implies that the annealing and the Al doping help to improve the electrical conductivity and optical properties as well. The minimum value of resistivity was 1.10 × 10^‑4 Ω cm for 0.5 at. % AZO film and transmittance was greater than 96% in the visible region. The present value of resistivity is comparable to the lowest values for AZO films reported in open literatures. All the films prepared by this method have a good crystalline structure and homogenous surface. We proposed that the substitution of Al in the ZnO lattice has positive effects in terms of increasing the free electron concentration. At atmospheric pressure, the electrospraying method was confirmed to be suitable for the preparation of AZO films with low resistivity and high transmittance.