Fabrication and characterization of c-axis-oriented transparent conductive nanocrystalline AZO thin films by rf magnetron sputtering

Abstract

Using high density ZnO:Al₂O₃ (AZO) target (94%) and without introducing any reaction oxygen, (001)-oriented transparent conductive AZO thin films are prepared by rf planar magnetron sputtering deposition on soda-lime glass. The structural, electrical and optical properties of the films deposited and annealed at different conditions are characterized with various techniques. The as-deposited and post-deposition annealed thin films have highly c-axis-orientated growth with hexagonal structure. Samples deposited at below 360°C are very smooth with spherical grains about tens nano-meters, the crystallization has been improved with vacuum annealing. The experimental results show that AZO thin films with optical transmittance of above 85% at wavelength of 550 nm and electrical resistivity of 10^-4 Ωcm order were achieved by deposition at substrate temperature of 360°C and subsequently annealed at 450°C for 2 h in vacuum pressure of 10^-5 Torr. With increase of the deposition temperature or post-deposition annealing in vacuum, the carrier concentration of AZO thin film increases, and the absorption edge in transmission spectra shifts toward the shorter wavelength side (blue shift).