Optical, electrical and structural properties of aluminum-doped nano-zinc oxide thin films deposited by magnetron sputtering

Abstract

Nano transparent conducting aluminum-doped zinc oxide (AZO) thin films were deposited on glass substrates by the magnetron sputtering technique. The thin films were characterized with X-ray diffractometer, scanning electronic microscopy, four-point probe and UV–Visible spectrophotometer. The dependence of structural, morphological, optical and electrical properties on substrate temperature was investigated. The results show that all the thin films have hexagonal wurtzite structure with highly c-axis orientation. The structural and optoelectrical properties of thin films are observed to be subjected to the substrate temperature. The AZO thin film deposited at the substrate temperature of 370 °C possesses the best optoelectronic properties, with the lowest resistivity of 6.12 × 10−4 Ω cm, the minimum microstrain of 0.92 × 10−3, the highest average visible transmittance of 85.1 % and the maximum figure of merit of 1.03 × 104 Ω−1 cm−1. The optical bandgap of thin films was estimated from Tauc’s relation and observed to be an increasing tendency with the increment of the substrate temperature. Furthermore, the optical constants such as refractive index, extinction coefficient, dielectric constant, dissipation factor and optical conductivity were determined by the pointwise unconstrained optimization method, and the dispersion behaviour was studied by the Wemple–DiDomenico single-oscillator model.