Study On The Construction Of Semiconductor Oxide With Junction Microstructures And Their Gas Sensing Properties

With the rapid development of our country's economy,the people's living standard is constantly improving.The quality of gas environment attract people's attention.Gas sensor is a kind of device that can identify and monitor gases in the environment,which is widely used in industrial safety,medical diagnosis,air quality monitoring,agricultural production and so on.Gas sensitive material is the core of gas sensor.Thus,the research and development of high-performance sensing materials plays an important role in promoting the practical application of gas sensors.The gas sensing properties of sensor are affected by the microstructure and composition of the semiconductor oxide.There are many advantages of core-shell structure.On one hand,core-shell?hierarchical?structure usually owns high specific surface area,which could provide sufficient surface adsorption sites for gas molecules.On the other hand,core-shell structure ensures the compatibility between core and shell,utilizing the particular characteristic of inner-core and outer-shell individually at the same time.From the point of view of material composition,the design of junction structure can bring special electronic effect,chemical effect and geometric effect to the composite material,resulting in enhancing the sensitivity.This paper starts with four kinds of metal oxides and modifies their components to junction sensitive materials on the basis of constructing core shell?hierarchical?structure.The morphologies and composition of MOS and their gas-sensing properties are reviewed in detail,which provides a potential strategy for developing new sensitive materials.The works of this paper are listed as follows:1.Four kinds of core shell structures based on different metal oxide semiconductors?MOSs?were designed and synthesized.They are SnO₂ core shell,Co₃O₄ core shell,NiO core shell and Cu₂O core shell structure.The design aims at improving the recognition function,conversion function and utilization efficiency of sensitive materials to gas molecules.Moreover,the influence of the microstructure of the material on its sensitivity was also studied.The core-shell structure effectively solves the problem of the agglomeration of nanoparticles due to the van der Waals force on the surface,resulting in providing sufficient reaction space for the diffusion,adsorption and electron transfer of gas molecules,and finally improving sensitization of materials.The sensitivity was greatly improved.2.On the basis of core-shell structure,SnO₂ sensitive materials with hetero-junction were prepared by composited with TiO₂ and C respectively.N-n hetero-junction was formed among particles in SnO₂-TiO₂.N-p hetero-junction is formed between particles in SnO₂/C core-shell structure.In this paper,the sensitization mechanism of core-shell structure on materials is studied.The formation of hetero-junction at the interface of nanoparticles effectively solves the problem of poor selectivity of single SnO₂ material.3.P-n and p-p heterostructures were formed by combining In₂O₃ and MWCNTs with p-type Co₃O₄,respectively.In the experiment,the effects of different component proportions and surface defect states of metal oxide particles on the sensitive properties are discussed in detail.The dependence of structure and components on the sensitivity of gas sensor is further studied.The sensitivity of Co₃O₄ material was improved and the working temperature was reduced through the construction of junction.4.ZnO was introduced into p-type NiO to form a core-shell structure containing p-n hetero-junction.The effects of the introduction of ZnO on the structure and gas sensing properties of sensitive materials are discussed in detail.In addition,NiO material was still used as the main sensitive material to further synthesize a new composite sensitive material containing two kinds of hetero-junctions?n-n and n-p?,which enriched the research system of junction materials and provided a foundation for in-depth study of interface effects under the coexistence of different hetero-junctions.The junction structure improves the sensitivity of the material,including increasing of the sensitivity and the decreasing of the operating temperature.In this paper,material design,sample preparation,sensitivity testing and mechanism analysis are described in detail.The relationship between the microstructure,phase components and sensitive properties of materials are clarified.The gas-sensitive material system and gas sensing mechanism are enriched,and more new ideas are provided for the research and application of gas sensors.