Temperature-dependent growth and properties of W-doped ZnO thin films deposited by reactive magnetron sputtering

Tungsten doped zinc oxide (WZO) thin films have been deposited by pulsed direct-current (DC) reactive magnetron sputtering technique. The microstructure, surface morphology, optical and electrical properties of WZO thin films were investigated at different substrate temperatures. Experimental results indicate that the substrate temperature is the key factor for fabricating high quality WZO thin films. The WZO thin films exhibit hexagonal wurtzite structure with (0 0 2) preferential growth orientation, and become more smooth at a much higher temperature. The optimized WZO thin film obtained at the substrate temperature of 300 degrees C exhibits a high Hall mobility of 27.5 cm(2) V-1 s(-1), a low sheet resistance of 23.3 Omega/square, and an average transmittance of 82.0% in the wavelength range from 400 to 1500 nm. The X-ray photoelectron spectroscopy (XPS) reveals that W element exists only in the oxidized state of W6+ in WZO thin films obtained at all the substrate temperatures, and Zn exists in a mixture state of oxidized and metallic formation. (C) 2013 Elsevier B.V. All rights reserved.