Abstract
WO 3 has attracted attention because of its potential for NO x gas sensing. Thin films of WO 3− x were prepared by KrF excimer pulsed laser deposition technique on quartz and Al 2O 3 with Pt electrode. The films were deposited at various substrate temperature, oxygen pressure and conditions of the post-annealing. The substrate temperature over 400 °C was needed for the crystallization of the WO 3− x thin film. The crystal structure of the WO 3− x thin film deposited at oxygen pressure of 100 mTorr and the substrate temperature of 400 °C was tetragonal phase, however, the films deposited at the oxygen pressure over 200 mTorr showed triclinic phase. The atomic force microscopy image of the WO 3− x thin film post-annealed in oxygen atmosphere for 30 min showed an average grain size of 268 nm. It was approximately two times larger than that of the as-deposited film. The maximum sensitivity ( R NO/ R N 2 ) of the as-deposited triclinic WO 3− x thin film gas sensor in the NO gas (60 ppm in N 2) was 4.2 at an operating temperature of 200 °C.
Published Version
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