Highly oriented VO2 thin films prepared by sol-gel deposition

Highly oriented VO2 thin films were grown on sapphire substrates by a sol-gel method which includes a low-pressure annealing in an oxygen atmosphere. This reduction process effectively promotes the formation of the VO2 phase over a relatively wide range of pressures below 100 mTorr and temperatures above 400 degrees C. X-ray diffraction analysis showed that as-deposited films crystallize directly to the VO2 phase without passing through intermediate phases. VO2 films have been found to be with [100]- and [010]- preferred orientations on Al2O3 ((1) over bar 012) and Al2O3 (10 (1) over bar0) substrates, respectively. Both films undergo a metal-insulator transition with an abrupt change in resistance, with different transition behaviors observed for the differently oriented films. For the [010]- oriented VO2 films a larger change in resistance of 1.2 x 10(4) and a lower transition temperature are found compared to the values obtained for the [100]-oriented films. (c) 2005 The Electrochemical Society. [DOI: 10.1149/ 1.2135430] All rights reserved.