Influence of substrate and film thickness on structural, optical and electrical properties of ZnO thin films

Transparent Zinc Oxide (ZnO) thin films have been grown on Si (100) and Sapphire (0001) substrates by RF magnetron sputtering for different growth time intervals (10, 30 and 60 min) to study the substrate and thickness effects. All the films have been grown at a substrate temperature of 450 degrees C. It has been found that the average growth rate on Si (100) substrate (8.6 nm/min) is higher than that on Sapphire (0001) substrate (2.6 nm/min) in an identical growth condition which clearly shows the virtual role of substrates. The lower growth rate on Sapphire (0001) suggests that the increasingly ordered and uniform growth due to less lattice mismatch. The grown films have been characterized by X-ray diffraction (XRD), Reflectance, Photoluminescence (PL) and Hall measurements. The XRD result (FWHM) reveals that for lower growth time, the films grown on Si (100) is better than on Sapphire (0001). Conversely, for higher growth time, the films grown on Sapphire (0001) is better than on Si (100). The variation of strain behavior due to thickness on both substrates has been justified by UV-Vis reflectance, photoluminescence and Hall effect measurements. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim