Highly oriented VO2 thin films were grown on sapphire substrates by the sol-gel method that 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 400oC. 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(1012) and Al2O3(1010) 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 1.2x10^4 and a lower transition temperature are found compared to the values obtained for the [100]-oriented films.
@article{arxiv.cond-mat/0510267,
title = {Highly oriented VO2 thin films prepared by sol-gel deposition method},
author = {Byung-Gyu Chae and Hyun-Tak Kim and Sun-Jin Yun and Bong-Jun Kim and Yong-Wook Lee and Doo-Hyeb Youn and Kwang-Yong Kang},
journal= {arXiv preprint arXiv:cond-mat/0510267},
year = {2007}
}