Optimization of a SAW metal oxide semiconductor gas sensor

A simple theoretical model is applied to the problem of a SAW (surface acoustic wave) gas sensor which operates on the principle of conductivity changes within the sensing film. The model allows the prediction of SAW sensor response for a film of known conductivity variations, and the theoretical value of SAW velocity change agrees very well with that determined by experiment. The electroacoustic attenuation was also determined to be a significant factor in designing a SAW sensor. SAW sensor response can be optimized by designing the device such that the sheet conductivity of the film is within some region dependent upon the substrate material. A WO/sub 3/ film could be designed to have a sheet conductivity within a specific range by tailoring parameters such as film thickness, doping, and heat treatment. A sensor consisting of an ST-cut SiO/sub 2/ substrate and a WO/sub 3/ film selectively sorbent to H/sub 2/S was investigated. The SAW gas sensor is configured so that the film sheet conductivity and sensor response are measured simultaneously upon exposure to H/sub 2/S. Specific operating conditions are obtained that optimized the SAW gas sensor response.<
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