Study On Discretized Hemispheric Resistance-Type Gas Sensor

For the past two to three decades, there has been a constant development in gas sensor technology in our country. However, we can still hear news about gas leakage, explosion, poisoning, etc., from time to time. Therefore, we have to develop quick and accurate detection of gases and atmosphere, whether in industrial production or family life, to ensure a timely hazard warning system, and ultimately guarantee the safety of people's lives and property.As an important variety of sensor, gas sensor has received widespread attention, and getting more and more widely used. Consequently, the requirement for response speed of gas sensors is gradually becoming stricter. In order to improve the response speed, the sensitive structure is optimized in this paper.After the analysis of gas sensing mechanism of semiconductor film, a new model of sensitive structure of gas sensors, based on the measures taken to enhance the response speed of gas sensors, is presented. Based on the traditional continuous flat sensitive structure, the top half of it is discretized to become a discretized hemispheric array structure, with the lower half left unchanged, giving the whole sensitive structure a 3D-sensitive effect, and consequently enlarging the contact surface between the gas and the structure. As the contact surface is enlarged, more gas molecules can get to the surface of the sensitive structure per unit time, thus enhancing the redox reaction, and then causing a greater variation of the conductance per unit time, which finally accelerates the response of gas sensors. A diffusion equation of the hemisphere based on the diffusion theory, is then established, after which the response times of the gas sensors with improved and traditional sensitive structure are respectively analyzed and compared.The simulation results show that when the thickness of the traditional continuous flat sensitive structure H is twice the diffusion depth a, and the thickness of the continuous flat of the improved structure h, as well as the radius of the hemispheres r, is equal to a, the improvement reduces the response time by more than one half, leading to the conclusion that gas sensors with discretized hemispheric array sensitive structure have better response time.In order to further improve the response speed, the thickness of the continuous flat of the previously improved structure h, as well as the radius of the hemispheres r, is adjusted. The simulation results show that reducing h and/or r improves the response speed, and when h is reduced to 1/4 of the diffusion depth a, and r to 1/3 of a, the gas sensor reveals the best performance, especially with respect to the response time.