Abstract

The vanadium oxide system is well known for its multiphase behaviour. Many compositions are known, ranging from VO_0.2 to V₂O₅. Several of these materials exhibit semiconductor-metallic phase transitions at temperatures between 10 and 400K, the most well known being found in the case of vanadium dioxide at 341K. A large number of studies have addressed the properties of thin films of VO₂ using material deposited by a number of different techniques, but there is no systematic study reported of the sensitivity of the phase transition to composition in the range close to x=2.0. This work seeks to address this issue using material deposited by reactive sputtering using an RF planar magnetron source under ultra-clean (UHV-type) conditions. The problems posed in the use of reactive sputtering for the deposition of such oxide films arise because of the affinity of the metal target for the reactive gas used during sputtering which results in a highly non-linear process characteristic as discussed by Berg [1] and others. For the deposition of materials in their highest oxidation states (eg alumina, V₂O₅) etc), this doesn't usually present too much difficulty, since it is only necessary to provide sufficient reactive gas to overcome the level of poisoning at the target surface. In the case of vanadium oxide however, the control of composition is of paramount importance in achieving the optimum film properties.

© 1992 Optical Society of America