The Study Of Zno Gas Sensor Enhanced By UV Light

Gas sensors had been applied in detecting toxic gas、combustible gas、humidityand so on. The gas seosors based on metallic oxide usually has bad performance inroom temperature, so the gas sensors need to work at high temperature in order to getbetter performance. However, gas sensors working at high temperature is notapplicable in some areas, such as some places containing explosive gases. On theother hand, gas sensor worked at high temperature is difficulty inmicrominiaturization and integration. So we need to adopt new approach to activatethe sensing materials instead of heating. The light irradiation can increase the freecarrier concentration throughout the semiconductor, increase the rate of gasadsorption and desorption, and activate the sensing materials by changing the surfacestate of sensing materials. It is a great way to improve the performance of the gassensors instead of heating.Compared with gas sensor enhanced by heating, however the gas sensorsenhanced by UV light still have bad performance, such as lower response and longerresponse time and recover time. At present, the gas sensor enhanced by UV light stillhave not been good enough to meet the actual need of application. So in this paper,we developed a kind of gas sensor based on ZnO, and try to increase the response ofthe gas sensor through the following means:1. It is well know that the sensing mechanism of ZnO is based on the fact thatchemical interaction of gas molecules with the semiconductor surface accompanywith charge exchange, which leads to changes in the electrical conductivity. The gassensors based on porous metal oxides usual have better performance as the large specific surface area is favor for the absorption of gas molecular. Porous ZnO issynthesized by a facile template-free hydrothermal method combined with subsequentcalcination and its HCHO sensing performance is studied, the result shows that theporous ZnO activated by UV light shows significant response for HCHO even atroom temperature.2. α-Fe2O3is sensitive to the surrounding gas, however the mean free path ofelectrons ofα-Fe2O3is short；ZnO has high carrier mobility and great in chargertransport. So we fabricated ZnO/α-Fe2O3composite, and studied its response forformaldehyde under the irridation of UV light. the result shows that the ZnO/α-Fe2O3activated by UV light shows significant response for HCHO even at room temperatureand the response for100ppm formaldehyde is3.5.3. ZnSnO3is a kind of gas-sensing materials which has greater performancethan ZnO、SnO2and In2O3, so we fabricated ZnSnO3nanocage by means ofhydrothermal method, and studied its response for formaldehyde under the irridationof UV light. The result showed that ZnSnO3has great response for formaldehyde.