Preparation And Research Of Gas Sensor Based On Nano InN-In₂O₃ Composite

With the rapid development of the national economy,residents’requirements for travel safety,living quality,and air environment continue to increase,and the requirements for sensors for toxic and harmful gases such as ethanol,formaldehyde and NO2 with high sensitivity and strong anti-interference are becoming higher and higher.Among all kinds of gas sensors,semiconductor sensors have always been research hotspots due to their low production cost,low power consumption,high sensitivity and strong stability.Gas-sensitive materials are the core of gas sensors,and improving the sensitivity of gas-sensitive materials through doping and compounding is one of the important means to improve the performance of gas sensors.In₂O₃ is an important gas-sensitive material,and further improving its sensitivity is also one of the key issues continuously explored in the industry.InN is a new type of direct bandgap compound semiconductor with smaller effective electron mass,bandgap width,and larger electron mobility.If InN and In₂O₃ are combined,through complementary advantages,it is theoretically possible to develop a new type of composite metal oxynitride gas-sensitive material,to achieve high-performance detection of harmful gases.Therefore,this paper innovatively proposes the use of InN to modify In₂O₃ to enhance its gas-sensing response ability and construct a new type of ultra-high-sensitivity gas sensor.In this thesis,the material growth process of nitriding and then oxidizing was used to prepare nano-InN-In₂O₃ heterojunctions with different morphologies,and use them as sensitive bodies to make new miniature chip planar sensors and study their gas-sensing properties,Used for fast and low temperature detection of ethanol（vapor）,formaldehyde（vapor）and NO₂ gas.The main research work and results of the thesis are as follows:1.The In₂O₃ nanomaterial as the precursor of the composite material was prepared by the hydrothermal method,and the XRD,SEM,and TEM characterization were performed.The results showed that the prepared In₂O₃ nanomaterial was a pure four-cube structure;2.The InN material as the base material was obtained by nitriding the prepared In₂O₃,and the morphology and structure of the material were characterized by XRD,SEM,TEM,EDS,XPS,PL,etc.The results showed that the obtained performance The InN material of the base material is a pure InN nanorod structure;3.By oxidizing the substrate material,a nano-InN-In₂O₃ pine-like structure composite material was successfully grown on the substrate,and a new type of micro chip planar sensor was made using it as a sensitive body,and the gas sensitivity test was performed.The results show that when the operating temperature is at least 50℃,the sensitivity of the sensor to 1ppm ethanol reaches 49,the response-recovery time is only 1 second,and the detection limit is as low as ppb;4.By changing the oxidation conditions,successfully prepared a bottle-like structure nano-InN-In₂O₃ composite material,and used it as a sensitive body to make a miniature flat chip sensor,and conducted a gas sensitivity test.The results show that the sensor has a very high sensitivity to formaldehyde.When the working temperature is as low as 75℃,the sensitivity can reach 112 for 600ppb formaldehyde,and the response time is only 2 seconds.When the detection concentration is as low as 100ppb,the sensitivity can still reach 12;5.Further changing the oxidation conditions,the InN-In₂O₃ cavity nanostructure composite material was successfully obtained on the InN substrate,and made into a miniature flat chip sensor using it as a sensitive body,and the gas sensitivity performance test was carried out.The results show that the sensitive material has a high sensitivity to NO₂ gas,the sensitivity to 50ppm NO₂ gas can reach 1021,the response-recovery time is only 1.5 seconds and 2 seconds,and the best test temperature is 100℃.Finally,the gas-sensitivity mechanism of InN-In₂O₃ composite material is analyzed.We believe that the inherent reason that the introduction of InN can significantly improve the response of In₂O₃ to the target detection gas is that during the preparation of the InN-In₂O₃ composite material,an I-type band alignment will be formed at the interface where the valence band edge energy of In₂O₃ is lower than that of InN.Due to the formation of heterojunction,the formation of a large number of interface defects oxygen,the increase of electron concentration and migration rate causes more electrons to react with O₂ adsorbed on the surface of the material,forming more O^-and O ion.In summary,the nano-InN-In₂O₃ composite material with"pine branch","bottle",and"cavity"structure grown on the pure InN nanorod structure substrate is used as a gas-sensitive material,which is resistant to ethanol,formaldehyde,and NO₂.Each has a fast response and a higher sensitivity at a lower operating temperature.Compared with In₂O₃-based gas-sensing materials in the literature,it is found that the three composite materials have excellent gas-sensing properties.It is proved that the combination of InN and In₂O₃ can effectively improve the gas-sensing performance of In₂O₃,in order to further improve the gas-sensitive properties of In₂O₃ sensitive materials Provides new research ideas.