Development of a micromachined hazardous gas sensor array

The objective of this work was to develop a micro-hotplate-based gas sensor array for detecting ammonia (NH3), hydrogen sulfide (H2S), and methane (CH4) gases. Sensing film fabrication parameters were studied with micro-hotplates based on resistive temperature detectors and microelectro-mechanical system (MEMS) micro-hotplate arrays. SnO2/Pt, WO3/Au, and ZnO sensing films were found sensitive to the target gases NH3, H2S, and CH4, respectively, but had some cross-sensitivity. Other limitations of the sensing films were baseline drift, high resistance, and recovery time. Sensor array responses to the gases were unique, which should allow selectivity to be obtained by pattern recognition.