Study On The Low Power Consumption Semiconductor Resistive Gas Sensors

A gas sensor is a device that detects the presence of gases in an area,often as part of a safety system.This type of device is used widely in environmental monitoring and protection(air quality and motor vehicle exhaust detection,etc.),industry production(industrial waste gas monitoring,etc.),and security(flammable and explosive,poisonous and harmful gas detection,etc.)areas.However,low sensitivity to low concentration gas,poor selectivity and high power consumption limit the application of gas sensors.Recently,with the rapid development of industrialization,micro-miniature,integrated and low power consumption gas sensors are needed.For this purpose,two approaches are used:exploring new nice gas sensing materials working at room temperature(RT,25 ?),for example,porous silicon(PS);develp and design low power consumption gas sensing devices,for example,microfabricated heater platform.Herein,PS/V2O5 nanorods,Au-functionalized PS/V2O5 nanorods,PS/WO3 nanowires composites,as gas sensing material working at room temperature,are fabricated,and low power comsumption WS2 aerogel-based gas sensor with microheater is prepared.The relevant research results and innovation points are as follows:PS/V2O5 nanorods composite is prepared by a heating process of as-sputtered V film on p-PS(pore diameter?1.2 ?m)in air.The growth mechanism of V2O5 nanorods is analyzed systematically.V film is oxidized gradually in air and crystallizes with heating temperature increasing;porous silicon is helpful for the growth of V2O5 nanorods nuclear;the optimum growth temperature of nanorods is 600 ?.This composite shows excellent NO2 sensing performances at RT,indicating p-type behavior.V2O5 nanorods can increase the sensitivity of the PS to NO2 at 25 ? by around 6 times,due to the heterojunctions between V2O5 and PS.Au-functionalized porous silicon/V2O5 nanorods(PS/V2O5:Au)composite is fabricated by heating double-layer V-Au film on PS(pore diameter?1.2 ?m)in air.Au nanoparticles are non-uniformly dispersed onto surface of the composite.With increasing of the thickness of Au film,the length of V2O5 nanorods decreases.The PS/V2O5:Au sample exhibits an improved NO2-sensing performances in sensitivity,stability,and selectivity at room temperature,compared with the pure PS/V2O5 nanorods,due to the "overflow effect" of Au.As Au content increases,NH3 sensitivity of the composite is improved,because of the effect of both Au and V2O5 nanorods structure.P-type heterojunctions structure based on n-PS/n-WO3 nanowires composite is achieved,by a two-step heating process of as-sputtered W film on n-PS(pore diameter?50 nm).The composite shows an excellent response,great selectivity and stability to NO2 at 25 ?.The unnormal p-type behavior is due to the strong oxygen adsorption on the surface of the composite and the heterojunctions between n-PS and n-WO3.WO3 nanowires increases the sensitivity of the PS to NO2 at 25 ? by 3-5 times,and improves the selectivity of the PS to N02.Low power gas sensor is prepared by investigating porous tungsten disulfide(WS2)aerogel with high surface area on micro-heater platform.The gas sensing performances of this sesnor at 20? is weak,while the optimum sensing temperature is about 250 ?(?4.6 mW),indicating p-type behavior.Responses of the sensors to NO2,O2,H2,NH3 and water vapor are achieved in dry air with poor selectivity.While the sensor shows excellent NO2 selectivity in dry N2.O2 is helpful for enhancing the sensitivity and recovery of the sensor to reducing gasessuch as H2,NH3 and water vapor,while has no effect on the NO2 sensing performances of the sensor.WS2 aerogel can be used to detect NO2 in anaerobic environment.