Highly Oriented VO[sub 2] Thin Films Prepared by Sol-Gel Deposition

Abstract

Highly oriented VO 2 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 VO 2 phase over a relatively wide range of pressures below 100 mTorr and temperatures above 400°C. X-ray diffraction analysis showed that as-deposited films crystallize directly to the VO 2 phase without passing through intermediate phases. VO 2 films have been found to be with [100]- and [010]-preferred orientations on Al 2 O 3 (1012) and Al 2 O 3 (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 VO 2 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.