Study Of MOS Gas Sensors Fabrication Process And The Application Of Cotton Template WO₃

MOS gas sensors are the foncus of gas sensor research and possess wide application prospect. Now gas sensing materials with excellent performance, novel fabrication techniques are emerge in large numbers, but they have to face high cost, low yield and stability problems when it takes into practical application. In this paper we choose screen printing techniques and co-planar gas sensor structure, using cotton template C-doped WO₃ nanotube as gas sensing material, we successfully fabricated high performance, low power consumption, low cost, high yield WO₃ co-planar gas sensor.Fabricated stack structure device doesn't have much advantage in power consumption and thermal response when comparing with co-planar structure. In addition stack structure involves complicated process. Further study the influence of the length of interdigited electrode(L) and packing structure on co-planar gas sensor found that below 350℃gas sensor with L=0.4mm has the best gas sensing performance, above 350℃gas sensor with L=0.8mm has the best gas sensing performance. Metallic support is one of key factors of high power consumption, using hollow structure the power consumption decreased 100mW, and the thermal response time reduced 245s.Study the prepation of MOS gas sensors from selection of raw material, process flow and process parameters, and the results shows that we should choose Au slurry and stainless screen when fabricating MOS gas sensors; Standardization of single device size, the design of alignment mark and pre-cutting ceramic plate can improve the printing efficiency and qualification rate, at the same time avoid contamination of gas sensor films; The suitable distance between substrate and screen for nylon and stainless screen were 1.5mm and 1.0mm respectively, the films should leveling 30 min in air after printing and later dry in 180℃.The optimum ration of cotton template WO₃ powder and organic carrier to prepare WO₃ gas sensing slurry is 7.5:2.5. FESEM characterization of 450℃⁶50℃annealed samples found the grain size increase with annealing temperature, thus the corresponding gas sensing performance descrease. Detail gas sensing measurement of 450℃annealed samples show that they are highly sensitive and selective to toluene, xylene and ethylbenzene, quick response and fast recovery, so they are prospective in practical application.