Effects of substrate heating and vacuum annealing on optical and electrical properties of alumina-doped ZnO films deposited by DC magnetron sputtering

Abstract

Alumina-doped zinc oxide (AZO) films have wide range of applications in optical and optoelectronic devices. AZO films have advantage in high transparency, high stability to hydrogen plasma and low cost to alternative ITO film. AZO film was prepared by direct-current (DC) magnetron sputtering from ceramic ZnO:Al₂O₃ target. The AZO films were compared in two different conditions. The first is substrate heating process, in which AZO film was deposited by different substrate temperature, room temperature, 150 °C and 250 °C. The second is vacuum annealing process, in which AZO film with deposited at room temperature have been annealed at 250 °C and 450 °C in vacuum. The optical properties, electrical properties, grain size and surface structure properties of the films were studied by UV-VIS-NIR spectrophotometer, Hall effect measurement equipment, x-ray diffraction, and scanning electron microscopy. The resistivity, carrier mobility, carrier concentration, and grain size of AZO films were 1.92×10^-3 Ω-cm, 6.38 cm²/Vs, 5.08×10²⁰ #/cm³, and 31.48 nm respectively, in vacuum annealing of 450 °C. The resistivity, carrier mobility, carrier concentration, and grain size of AZO films were 8.72×10^-4 Ω-cm, 6.32 cm²/Vs, 1.13×10²¹ #/cm³, and 31.56 nm, respectively, when substrate temperature was at 250 °C. Substrate heating process is better than vacuum annealed process for AZO film deposited by DC Magnetron Sputtering.