Effect of Sputtering Pressure on Al-doped ZnO Films by DC Magnetron Sputtering

Al-doped ZnO (AZO) films were deposited on the glass substrates by direct current magnetron sputtering using different sputtering pressures ranging from 0.2 Pa to 2.2 Pa. Microstructure, phase, electrical and optical properties of AZO films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), four-point probe and UV-Vis spectrophotometer, respectively. The results revealed that the deposition rate decreased with the increasing sputtering pressure according to Keller-Simmons model; the crystalline phase of all films was hexagonal wurtzite and the preferred orientation changed with the sputtering pressure; the surface morphology greatly depended on the sputtering pressure and the film deposited at 1.4 Pa showed low resistivity (8.4×10-4 Ω·cm), high average transmission and the highest Q, a criterion factor as the film figure of merit, which was the ratio between the normalized average transmission and the normalized resistivity.