Response of a ZnO single crystal rod-based chemical sensor for hydrogen sulfide.

A zinc oxide single crystal rod was grown by a thermal evaporation method for application as a chemical gas-sensing material in this study. Zinc acetate (20 wt%) impregnated over activated carbon was used as the precursor for the epitaxial growth of ZnO single crystal rods. The response tests were carried out across a range of sensing temperatures (100, 150 and 200 °C) and the hydrogen sulfide content (10.2-51.0 ppmv) was balanced with nitrogen gas. The response of the ZnO single crystal rods grown on the gas sensors varied with the H2S content and the sensing temperature. A high response for H2S was obtained at 150 and 200 °C due to the high reactivity between H2S and ZnO at high temperature. Since H2S absorption rate and ZnS oxidation rate over ZnO single crystal rods at 100 °C lower than that at 150 and 200 °C, the changing rate of electric resistance decreased with the decrease of temperature. Meanwhile, a different response, which is the changing rate of electric resistance for H2S absorption and ZnS oxidation over ZnO single crystal rods at 100 °C, was observed with changing amount of H2S in feed gas. Therefore, it was concluded that the ZnO single crystal rods based gas sensor is operated above 200 °C for the shortly response time.