| Through the technology of RF and DC reactive sputtering manufacture, H2S gas sensors have been developed on silicon substrate on which a heater made of Pt were attached. Experiments show both the nanosized WO3 and SnO2 based sensors are sensitive to H2S gas, but when it comes to sensitivity and response -recovery time, SnO2-based sensors are better than WO3-based sensors. A fairly long period of studies also shows that the two kinds of element are poorly stable whose sensitivities are varying with the change of the environmental temperature and relative humidity to which should be paid more attention in further research. Then an equation about sensitivity versus time is also presented. Performances of the elements indicate the properties of elements are relating to film thickness, sputtering power, sputtering time and sputtering pressure. But among the four factors have been displayed, the film thickness of sensing material has a decisive effect on feature of elements and a relatively optimal thickness is discussed whose range is 200-400A. The microstructures of these two kinds of material are characterized by XRD and TEM. The average grain size of WO3 is 17.51nm and the average grain size of SnO2 is 8.56nm. Pictures provided by TEM indicate the difference between WO3 and SnO2 on appearance. Surface-conductance model are introduced to illustrate the mechanism of the conductivity and the gas sensibility of semiconductor. We make clear the reason of the good selectivity of SnO2-based sensors is the selection of heating voltage and the Pt-heater acting as catalyst.
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