Effects of argon pressure and r.f. power on magnetron sputtered aluminum doped ZnO thin films

Abstract

In this study, aluminum doped zinc oxide (ZnO:Al) thin films were deposited on glass and silicon substrates by r.f magnetron sputtering technique, at room temperature. The effects or two important deposition parameters: argon gas pressure and r.f. power were investigated with small variations to understand the influence on electrical, optical and structural properties of the films. The resistivity values that were measured by four point probe, were 10(-3) Omega cm and the transparency values achieved, from ultraviolet-visible (UV-VIS) spectrophotometer, higher than 82% for all ZnO:Al thin films. Also, structural examinations using X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that the ZnO:Al thin films were (0 0 2) oriented. The crystallite sizes that were measured by XRD varied from 14 nm to 23 nm. For surface roughness investigations, atomic force microscopy (AFM) was used, and roof mean square (RMS) values were changed from 4.96 nm to as low as 0.59 nm. Thickness of the ZnO:Al thin films were determined with the help of scanning electron microscopy (SEM). Moreover, semiquantitative energy dispersive spectrometry (EDS) analysis was performed by TEM, and homogenous distribution of elements was identified. High resolution transmission electron microscopy (HRTEM) was helpful to understand the atomic level arrangement of the thin films. The observed results revealed that the maximum figure of merit (FOM) values were around 78,003 (Omega cm)(-1) for 0.3 Pa argon pressure and 165 W r.f. power, respectively. (C) 2014 Elsevier B.V. All rights reserved.