Low temperature response of nanostructured tungsten oxide thin films toward hydrogen and ethanol

Ahsan, M., Ahmad, M.Z., Tesfamichael, T., Bell, J.M., Wlodarski, W., & Motta, N. (2012) Low temperature response of nanostructured tungsten oxide thin films toward hydrogen and ethanol. Sensors and Actuators B : Chemical, 173, pp. 789-796.

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Abstract

Semiconducting metal oxide based gas sensors usually operate in the temperature range 200–500 °C. In this paper, we present a new WO3 thin film based gas sensor for H2 and C2H5OH, operating at 150 °C. Nanostructured WO3 thin films were synthesized by thermal evaporation method. The properties of the as-deposited films were modified by annealing in air at 300 °C and 400 °C.

Various analytical techniques such as AFM, TEM, XPS, XRD and Raman spectroscopy have been employed to characterize their properties. A clear indication from TEM and XRD analysis is that the as-deposited WO3 films are highly amorphous and no improvement is observed in the crystallinity of the films after annealing at 300 °C. Annealing at 400 °C significantly improved the crystalline properties of the films with the formation of about 5 nm grains. The films annealed at 300 °C show no response to C2H5OH (ethanol) and a little response to H2, with maximum response obtained at 280 °C. The films annealed at 400 °C show a very good response to H2 and a moderate response to C2H5OH (ethanol) at 150 °C. XPS analysis revealed that annealing of the WO3 thin films at 400 °C produces a significant change in stoichiometry, increasing the number of oxygen vacancies in the film, which is highly beneficial for gas sensing.

Our results demonstrate that gas sensors with significant performance at low operating temperatures can be obtained by annealing the WO3 films at 400 °C and optimizing the crystallinity and nanostructure of the as-deposited films.

Impact and interest:

30 citations in Scopus
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27 citations in Web of Science®

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ID Code: 58917
Item Type: Journal Article
Refereed: Yes
Keywords: Tungsten oxide, Thin films, Gas sensing, Thermal evaporation, Nanostructured
DOI: 10.1016/j.snb.2012.07.108
ISSN: 1873-3077
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2012 Elsevier S.A.
Copyright Statement: This is the author's version of a work that was accepted for publication in Sensors and Actuators B : Chemical. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Sensors and Actuators B : Chemical, [173, October 2012] 10.1016/j.snb.2012.07.108
Deposited On: 16 Apr 2013 01:19
Last Modified: 02 May 2013 01:03

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