Design And Device Performance Of P-type Semiconductor Gas Sensing Materials

In recent years,the research of semiconductor gas sensor has been widely concerned.However,most of the studies focus on n-type semiconductors,while the investigations of p-type gas sensing materials are relatively rare.And p-type gas sensing materials generally have some problems such as low sensitivity,poor selectivity and repeatability,etc.In view of this situation,this thesis aims to develop high-performance p-type semiconductor gas sensors,and three kinds of p-type semiconductor materials with unique morphology and good gas sensing properties were synthesized by a variety of simple means.Then,the gas sensitive properties were further improved and optimized by various methods,and the corresponding gas sensitive mechanism was studied.The major research results are as follows:(1)Urchin-like Ni Co₂O₄ microspheres were designed and synthesized by a hydrothermal method.The unique urchin-like hierarchical structure endow the material a large specific surface area,which provided abundant active sites for sensing reaction.In addition,the porous structure provides a large number of gas diffusion channels,which can accelerate the gas diffusion between the sensing layers.The Ni Co₂O₄ based gas sensors exhibit excellent selectivity,low limit of detection and excellent stability for trimethylamine detection.The gas sensing mechanism is explained by the model of hole accumulation layer.(2)Porous Co₃O₄ thin films with three-dimensionally ordered microstructure were synthesized via a sacrificial template method,and the gas sensing performance was improved by loading two noble metals.Specifically,the loading of Pt effectively improves the response of the material to NO₂ due to the spillover effect of Pt nanoparticles.While the loading of Rh significantly enhances the humidity resistance of Co₃O₄,which extends the application of the p-type metal oxide semiconductor gas sensor in high humidity environment.The mechanism of electron sensitization and chemical sensitization is used to explain the enhancement of sensing performance.(3)Two-dimensional WSe₂ nanosheets were prepared by a simple liquid exfoliation method and applied to a room temperature flexible gas sensor towards NO₂detection.The response of WSe₂ to NO₂ was significantly enhanced by ultraviolet excitation.Besides,even in extreme bending conditions,the gas sensor still maintains stable response and recovery,demonstrating excellent mechanical flexibility.The charge transfer model is used to explain the sensing mechanism and the improvement of sensing performance caused by ultraviolet light excitation.