Scientific Results

Gas sensing characteristics of Fe-doped tungsten oxide thin films

Year: 2012

Authors: Tesfamichael T., Ponzoni A., Ahsan M., Faglia G.

Autors Affiliation: Queensland Univ Technol, Fac Built Environm & Engn, Brisbane, Qld 4000, Australia;
Univ Brescia, SENSOR Lab, I-25133 Brescia, Italy;
IDASC CNR, I-25133 Brescia, Italy

Abstract: This study reports on the gas sensing characteristics of Fe-doped (10 at.%) tungsten oxide thin films of various thicknesses (100-500 nm) prepared by electron beam evaporation. The performance of these flims in sensing four gases (H-2, NH3, NO2 and N2O) in the concentration range 2-10,000 ppm at operating temperatures of 150-280 degrees C has been investigated. The results are compared with the sensing performance of a pure WO3 film of thickness 300 nm produced by the same method. Doping of the tungsten oxide film with 10 at.% Fe significantly increases the base conductance of the pure film but decreases the gas sensing response. The maximum response measured in this experiment, represented by the relative change in resistance when exposed to a gas, was Delta R/R=375. This was the response amplitude measured in the presence of 5 ppm NO2 at an operating temperature of 250 degrees C using a 400 nm thick WO3 :Fe film. This value is slightly lower than the corresponding result obtained using the pure WO3 film (Delta R/R = 450). However it was noted that the WO3:Fe sensor is highly selective to NO2. exhibiting a much higher response to NO2 compared to the other gases. The high performance of the sensors to NO2 was attributed to the small grain size and high porosity of the films, which was obtained through e-beam evaporation and post-deposition heat treatment of the films at 300 degrees C for 1 h in air. (C) 2012 Elsevier B.V. All rights reserved.


Volume: 168      Pages from: 345  to: 353

More Information: This work was supported by the Queensland Government Smart Futures Fund – National and International Research Alliances Program 2008-09 (NIRAP) \”Solar powered nano-sensors for data acquisition and surveying in remote areas\”. The Australian Institute of Nuclear Science and Engineering (AINSE) provided support for using their TEM facility and the Japanese Society for Promotion of Science (JSPS) provided funding for sensor development at Hokkaido University. Sensor electrodes were obtained from the Angstrom Laboratory at Uppsala University.
KeyWords: Tungsten oxide; Iron doping; Nanostructured thin films; NO2 gas sensing;
DOI: 10.1016/j.snb.2012.04.032

Citations: 46
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