Structural, electrical and optical properties of pulsed laser deposited VO2 thin films on R- and C-sapphire planes

Vanadium dioxide (VO2) thin films have been deposited on sapphire R (012) and C (001) planes using pulsed laser deposition. Growth conditions were optimised to obtain epitaxial growth. As in the case of most oxide materials, oxygen pressure and temperature are the main parameters allowing the formation of the well-known VO2 phase that exhibit the semiconducting to metallic transition at approximately 70 degreesC. Under optimised conditions, X-ray diffraction analysis revealed the highly (10 0) and (010) texture of the thin layers, respectively, on R-plane and C-plane. In both cases, DC conductivity and optical propel-ties in the 2-6 mum range have been measured as a function of temperature between room temperature and 90 degreesC. Optical indices in both insulating and metallic states have been calculated from the optical reflectivity and transmission data. These physical properties are discussed in relation to the crystalline quality of the VO2 thin films. (C) 2003 Elsevier B.V. All rights reserved.