Chemically deposited zinc oxide thin film gas sensor

Author: Chatterjee A.P.   Mitra P.   Mukhopadhyay A.K.  

Publisher: Springer Publishing Company

ISSN: 0022-2461

Source: Journal of Materials Science, Vol.34, Iss.17, 1999-09, pp. : 4225-4231

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Abstract

Zinc oxide (ZnO) thin films were prepared by a low cost chemical deposition technique using sodium zincate bath. Structural characterizations by X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) indicate the formation of ZnO films, containing 0.05–0.50 μm size crystallites, with preferred c-axis orientation. The electrical conductance of the ZnO films became stable and reproducible in the 300–450 K temperature range after repeated thermal cyclings in air. Palladium sensitised ZnO films were exposed to toxic and combustible gases e.g., hydrogen (H_2), liquid petroleum gas (LPG), methane (CH_4) and hydrogen sulphide (H_2S) at a minimum operating temperature of 150 °C; which was well below the normal operating temperature range of 200–400 °C, typically reported in literature for ceramic gas sensors. The response of the ZnO thin film sensors at 150 °C, was found to be significant, even for parts per million level concentrations of CH_4 (50 ppm) and H_2S (15 ppm).