| In this dissertation,the mechanism of pyroelectric enhancement of AlN thin films for infrared detection is studied,the orientation regulation and doping technology of AlN thin films are carried out,and the preparation and development of MEMS pyroelectric infrared detector are developed.The development of NDIR gas-sensitive module based on pyroelectric infrared detector and the application verification of automobile power battery runaway warning are preliminarily realized.The development of thin-film pyroelectric detectors has been mainly carried out as follows:Theoretical analysis and model construction of thin-film MEMS pyroelectric detector are firstly carried out.On this basis,COMSOL finite element simulation software is used to optimize the structure of the detector.Next,key process development and device preparation are carried out.The specific research content is as follows:(1)Analyze the pyroelectric properties and enhancement factors of AlN materials,starting from the spontaneous polarization effect,with a focus on theoretical analysis of crystal orientation and Sc doping enhancement mechanism;On the basis of in-depth analysis of the theoretical model of pyroelectric detectors,the theoretical calculation of the AlN pyroelectric detector was carried out to analyze the influence of the pyroelectric coefficient,film area,thickness and relative dielectric constant of the detector on the performance of the AlN pyroelectric detector,which provides theoretical support for the development of high performance AlN film materials and the development and preparation of the detector.(2)Based on the analysis of AlN material pyroelectric enhancement mechanism,Mo is selected as electrode material by comparing series material parameters,aiming at preparing polycrystalline multi-oriented AlN thin film,and doping 20%Sc to realize the growth of high pyroelectric performance Sc0.2Al0.8N thin film.According to the theoretical model of AlN pyroelectric detector,the structure optimization design of detector is carried out,and the basic device structure parameters are obtained.The device static and transient thermal simulation analysis is carried out by using COMSOL finite element software,and relevant parameter information such as surface temperature change,thermal response time and temperature distribution of detector are extracted to optimize and select the optimal structure parameters.(3)The orientation regulation and doping of Sc0.2Al0.8N materials were studied.AlN films were grown under different process parameters and characterized by XRD.The electrical properties and pyroelectric detector properties of Sc0.2Al0.8N films prepared by magnetron sputtering were studied.The voltammetry curves of Sc0.2Al0.8N films were tested,and the relative dielectric constant of Sc0.2Al0.8N films at different temperatures was measured.The relative dielectric constant of Sc0.2Al0.8N films at room temperature was 9.810.45.The pyroelectric coefficient of Sc0.2Al0.8N films was measured by dynamic current method.The pyroelectric coefficient of Sc0.2Al0.8N films reached 42.2 μC/(m2K)at 80℃,which is better than that of Sc0.2Al0.8N poly crystalline oriented films at 32μC/(m2K).(4)Designed and developed an amplification and filtering circuit based on AD8617 amplifier for noise reduction and signal reading of pyroelectric detectors;Afterwards,a prototype NDIR gas sensor module was developed using the Kalman filtering algorithm,achieving the detection of gas concentration.The test shows that the maximum error of the gas sensor is 0.02%.The developed NDIR gas sensor was applied to the thermal runaway analysis of lithium iron phosphate power batteries,and the battery thermal runaway alarm was about 580 seconds ahead of the BMS system,meeting the national standard GB 380312020.The research results of this paper indicate that gas sensors based on pyroelectric infrared detectors have broad application prospects in the field of thermal runaway warning and monitoring of automotive power batteries. |
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