Thin-film gas sensors based on high-temperature-operated metal oxides

Research into the characteristics of semiconducting metal-oxide films that are stable at high temperatures intensified with the aim of providing repro ducible-and reliable gas detection in various ambients. First, there is a d iscussion of the specifics relating to these materials, for example, the ef fect of grain-boundary barriers on the sensing mechanism, :the influence of humidity, and the temperature dependence of the sensing mechanism. Then, t he technology for the preparation of the gas sensors will be described. Exa mples that have already been implemented like lambda. detection, oxygen and NOx measurements in exhaust gases, detection of explosive and toxic gases in air, as well as hydrogen leakage detection are discussed. (C) 1999 Ameri can Vacuum Society. [S0734-2101(99)18104-1].