Chemical deposition of ZnO films for gas sensors

Zinc oxide (ZnO) thin films were prepared following a chemical, deposition technique using a sodium zincate bath. Structural characterizations by scan ning electron microscopy (SEM) and X-ray diffraction (XRD) indicate the for mation of ZnO film with a preferred c-axis orientation. The electrical cond uctance of the ZnO films became stable and reproducible in the 300-500 K te mperature range with two activation energy barrier values of 0.3 eV and 0.8 eV in the low temperature (300-420 K) and high temperature (430-500 K) ran ges, respectively. The ZnO films prepared by this method are highly resisti ve, indicating the presence of a large density of oxygen adsorbed acceptor- like trap states (O-2(-), O-, etc.). Palladium sensitized ZnO films were ex posed to hydrogen (H-2) with air as a carrier gas at different operating te mperatures ranging between 150-375 degrees C and the response is evaluated.