Electrical, optical and microstructural properties of transparent conducting GZO thin films deposited by magnetron sputtering

Thin films of transparent conducting gallium-doped zinc oxide (GZO) were deposited by magnetron sputtering technique onto glass substrates. The films were characterized by various methods to understand their microstructural, optical and electrical characteristics. The effects of substrate temperature on the physical properties of the films were investigated. The results show that the GZO films are polycrystalline in nature having a hexagonal wurtzite type crystal structure with a preferred grain orientation in the (0 0 2) direction. The substrate temperature significantly affects the crystal structure and optoelectrical properties of the films. The GZO film grown at the substrate temperature of 670 K has the largest crystal grain, the lowest resistivity and the highest figure of merit. Meanwhile, the optical constants, dielectric function and dissipation factor of the films were determined using the methods of Manifacier and Swanepoel. The dispersion behavior of the refractive index was studied in terms of the single-oscillator Wemple-DiDomenico (W-D) model, and the oscillator parameters of the films were achieved. Furthermore, the optical energy gaps were calculated by W-D model and Tauc's relation, respectively, and the values obtained from W-D model are in agreement with those determined from the Tauc's relation. (C) 2012 Elsevier B.V. All rights reserved.