Title: Role of the active layer thickness on the sensitivity of WO₃ gas sensors

Authors: K. Aguir; J. Guérin; N. Mliki; M. Bendahan

Addresses: IM2NP, CNRS 6242, Aix-Marseille University, FST, S152, 13397 Marseille, France. ' IM2NP, CNRS 6242, Aix-Marseille University, FST, S152, 13397 Marseille, France. ' LMOP, Faculty of Sciences, Tunis El Manar University, Tunis, Tunisia. ' IM2NP, CNRS 6242, Aix-Marseille University, FST, S152, 13397 Marseille, France

Abstract: Sensitive materials in gas sensors are often polycrystalline semiconducting oxides such as WO₃, SnO₂, CuO or ZnO. They are most often composed of nanometric grains. They can be deposited either as thin or thick films. The film thickness plays an important role in the response stability and sensitivity of sensors. It is now well accepted that the relationship between the surface and volume of the sensitive layer plays a major role in the efficiency of detection. Many experimental and theoretical works were reported in explaining the experimental sensitivity vs. thickness relationships reported for the gas sensors prepared by different fabrication techniques. In addition, significant changes can be expected by adding catalytic nanograins in small quantities on the surface of the sensitive layers. For example, cobalt nanograins deposited on the surface of WO₃ sensors produce an important change in the WO₃ conductance. Indeed, cobalt changes the conduction type of the sensors from n- to p-type. This paper describes the effect of reducing the size of the sensors and nanostructured sensitive materials on the sensor response.

Keywords: metallic oxide gas sensors; WO3; cobalt nanograins; selectivity; ozone; modelling; film thickness; tungsten trioxide; nanomaterials; nanotechnology.

DOI: 10.1504/IJNT.2012.045349

International Journal of Nanotechnology, 2012 Vol.9 No.3/4/5/6/7, pp.471 - 479

Published online: 06 Feb 2012 *

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