Effect of annealing on the structural, optical, and electrical properties of IZO films deposited by pulsed spray pyrolysis

Abstract

In this study, the influence of vacuum annealing at temperatures ranging from 300 to 500 °C on the chemical composition, structural, optical, and electrical properties of indium-alloyed ZnO (IZO) films was systematically investigated. Thin films were deposited by pulsed spray pyrolysis using molecular precursor solutions. The IZO films were characterized using scanning electron microscopy, x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX), Raman spectroscopy, optical spectroscopy, and Hall-effect measurements. XRD analysis revealed the formation of single-phase films with a hexagonal wurtzite structure, which was further confirmed by Raman spectroscopy. EDX analysis verified the successful incorporation of indium into the ZnO lattice. It was established that annealing at 400 °C produced the maximum coherent scattering domain size of L = 34.5 nm, the minimum microstrain value of ϵ = 3.5⋅10−3, and the lowest dislocation density of ρ = 5.8⋅1015 m−2. Optical studies demonstrated that the optical band gap remained nearly unchanged after thermal treatment, staying within Eg ∼ 3.33 eV. Furthermore, the influence of annealing on the extinction coefficient (k), refractive index (n), and the real (ϵ1) and imaginary (ϵ2) parts of the complex dielectric function was determined. The optimal electrical performance was achieved after annealing at 450 °C, where the resistivity decreased to ρ0 = 0.005 Ω·cm.