Chemically deposited zinc oxide thin film gas sensor

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) indicat e the formation of ZnO films, containing 0.05-0.50 mu m size crystallites, with preferred c-axis orientation. The electrical conductance of the ZnO fi lms became stable and reproducible in the 300-450 K temperature range after repeated thermal cyclings in air. Palladium sensitised ZnO films were expo sed to toxic and combustible gases e.g., hydrogen (H-2), liquid petroleum g as (LPG), methane (CH4) and hydrogen sulphide (H2S) at a minimum operating temperature of 150 degrees C; which was well below the normal operating tem perature range of 200-400 degrees C, typically reported in literature for c eramic gas sensors. The response of the ZnO thin film sensors at 150 degree s C, was found to be significant, even for parts per million level concentr ations of CH4 (50 ppm) and H2S (15 ppm). (C) 1999 Kluwer Academic Publisher s.