MEMS CO Gas Sensor Based On SnO₂

Higher requirements for gas sensors have been put forward with the development of science and technology.The gas sensors need higher response,higher selectivity,smaller size and lower energy consumption.For these reasons,development directions of sensors are miniaturization,array and intelligence.The MEMS gas sensors can meet the above development direction well.And the research on semiconductor sensors is gradually moving from scientific research to market application.Based on the enterprise MEMS chip platform,SnO₂ based CO gas sensors has been developed in this paper.SnO₂ materials were synthesized by nitric acid oxidation,the influences of ZnO,CeO₂ and ThO₂ to properties of SnO₂ gas sensors were investigated.The gas-sensing materials have been characterized and the gas-sensing properties of the MEMS sensors were investigated.The gas-sensing material MEMS type carbon monoxide sensors were selected.The specific research contents are as follows:（1）A simple nitric acid oxidation of Sn grains was used to synthesize SnO₂materials.The structure and morphology of the synthesized materials were examined by X-ray diffraction and scanning electron microscopy（SEM）,respectively.The gas-sensing properties tests showed that the materials were nanometer level of spherical particles,with the rutile structure of SnO₂.The gas-sensing properties of SnO₂ gas sensors to CO gas were examined.The results showed that the gas-sensing of the sensors to the target gas need to be further improved.（2）Different Zn-doped ratios of SnO₂ materials were prepared.The SEM and XRD results showed that there were no new phase and with the increase of the amount of Zn,the sensitive material particle size decreased.The gas-sensing properties tests showed that 10 wt.%was the optimum doping ratio;10 wt.%Zn-doped SnO₂ sensors response to CO increased from 610 m V to 940 mV at 1.5 V;the response times and the recovery times of 10 wt.%Zn-doped sensors to 100 ppm CO were below 7 s and 13 s,respectively.（3）The effect of CeO₂ to the gas-sensing of ZnO-SnO₂ materials was investigated.The results showed that the addition of CeO₂ significantly increased the response of the sensors to CO;6 wt.%CeO₂/ZnO-SnO₂ sensors response to 100 ppm CO increased from 940 mV to 1.52 V at 1.5 V;and the response times and the recovery times were below 7 s and 10 s,respectively.（4）The effect of ThO₂ to the gas-sensing of ZnO-SnO₂ materials was investigated.The gas-sensing properties tests showed that the addition of ThO₂ not only increased the response to CO,but also improved the selectivity.9 wt.%ThO₂/ZnO-SnO₂ sensors response to 100 ppm CO increased from 940 mV to 2.14 V at 1.5V;and the response times and the recovery times were below 5 s and 10 s,respectively.