AVS 45th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuM

Paper TF-TuM11
Characterization of Sol-Gel Prepared WO@sub 3@ Thin Films as a Gas Sensor

Tuesday, November 3, 1998, 11:40 am, Room 310

Session: Thin Films for Sensing and Data Storage
Presenter: M.Z. Atashbar, RMIT University, Australia
Authors: M.Z. Atashbar, RMIT University, Australia
Y. Li, RMIT University, Australia
M.K. Ghantasala, RMIT University, Australia
W. Wlodarski, RMIT University, Australia
Correspondent: Click to Email
Increasing awareness of well human being to environmental issues has attracted many scientific researches in the field of gas sensing. Tungsten trioxide (WO@sub 3@) thin films have promising electrical and optical properties for different applications, such as electrochromic displays, photolysises and gas sensing. The change of its conductivity due to the gas exposure has made itself a excellent candidate for nitrogen oxide (NO@sub x@) and ozone (O@sub 3@) sensing applications. In this study, the effect of the structure, micro-morphologies and composition of the WO@sub 3@ film on NO@sub x@ and O@sub 3@ sensing properties has been investigated. WO@sub 3@ thin films were prepared from starting precursors via sol-gel route in dry nitrogen atmosphere (@<=@10%RH). The used precursors was tungsten ethoxide (W(OC@sub 2@H@sub 5@)@sub 3@) with an analytic purity, which was dissolved in different analytical solvents. After ultrasonic mixing at room temperature for 1 hour the precursor solution was dropped on substrates and spin-coated at different speeds. The film thickness (20 to 200 nm) was controlled by changing the solution concentrations and spinning speed. After annealing at temperature of 400°C to 700°C crack-free WO@sub 3@ thin films were obtained. The morphology, microstructure, crystalline structure and composition of the deposited films were analyzed by SEM, XRD and RBS. The SEM analysis showed that that film is porous and the grain size is the rang of 20nm to 100nm. The RBS results indicated that the film is sub-stoichiometric. XRD analysis showed that the films are polycrystalline in nature. A detailed analysis of these results on the O@sub 3@ and NO@sub x@ sensitivity of the film has been discussed. The electrical resistance of the film has been examined for the detection of ozone in ppb level and NO@sub x@ ppm level.