Synthesis And Sensing Performance Enhancement Of Wide Band-gap Metal Oxide Semiconductor

With the rapid development of human society,there has been a significant increase in the demand for gas sensors in the fields of environmental monitoring,industrial production,and intelligent life.Metal oxide semiconductor gas sensors have gained significant attention due to their small device size,low power loss,low manufacturing cost,and good sensing performance.The gas-sensitive material is the core component of a gas sensor,and its properties directly determine the sensor’s performance parameters.In recent years,wide-bandgap metal oxide semiconductor（MOS）gas-sensitive materials have been extensively studied due to their fast electron mobility,excellent stability,and obvious resistance change.Despite their desirable characteristics,the gas-sensitive performance of wide-bandgap MOS still has room for improvement and cannot meet the increasingly strict application requirements.Therefore,it is crucial to identify appropriate sensitization strategies to enhance their performance.Moreover,the high synthesis temperature and complicated operation procedures of wide-bandgap oxide gas-sensitive materials limit their large-scale application,necessitating further simplification and improvement.This paper focuses on two typical wide-bandgap oxides,Ni Ga₂O₄ and Sn O₂,and explores their gas-sensitive properties.To enhance their gas-sensitive properties,two-dimensional Ni Ga₂O₄ ultra-thin nanosheets and Cd O/Sn O₂ heterogeneous composites were prepared using a simple co-precipitation method.The morphology control strategy and the oxide composite strategy were employed to enhance the gas-sensitive properties of the two materials,respectively.The mechanism behind the enhanced properties was analyzed from the aspects of specific surface area,material composition,surface adsorbed oxygen,and n-n heterogeneous structure,explaining the structure-activity relationship between the microscopic morphology,energy level structure and gas-sensitive properties of the materials.1.We synthesized Ni Ga LDH templates via the co-precipitation method and subsequently calcined them to obtain two-dimensional ultra-thin nanosheets of Ni Ga₂O₄.Due to their large specific surface area,multiple active sites,and ability to limit carrier migration,two-dimensional materials are highly conducive to improving gas-sensitive performance.The gas sensor based on the Ni Ga₂O₄ ultra-thin nanosheets exhibited an impressive response of 7.7 to 10 ppm xylene at a low working temperature of 190℃,with a remarkably low detection limit of 0.3 ppm.In addition,the sensor exhibited strong anti-interference ability towards formaldehyde,acetone and toluene gas at the same concentration,along with outstanding selectivity,repeatability,and long-term stability.We attribute the excellent gas-sensitive properties of the sensor to the large specific surface area of the two-dimensional ultra-thin nanosheet Ni Ga₂O₄ and the catalytic oxidation of xylene by Ni²⁺.The key points of this work are as follows:1)2D Ni Ga₂O₄ ultra-thin nanosheets were synthesized using LDH as template;2)the response and selectivity of Ni Ga₂O₄ to xylene were improved;3)The reason for the enhanced gas sensitivity of Ni Ga₂O₄ to xylene was revealed.2.In order to explore the influence of heterogeneous structure on the gas sensitivity of materials and improve the hydrogen sensitivity of Sn O₂,we have successfully synthesized a series of n-n type Cd O/Sn O₂ heterogeneous composites and Sn O₂,Cd O contrast materials by a simple coprecipitation method.We investigated the effect of varying Cd O content on the gas-sensitive properties of the composites.The Cd O/Sn O₂nanocomposite,with a mole ratio of 1:1,exhibited the highest sensitivity to hydrogen.At an operating temperature of 220℃,the sensor based on this material demonstrated a response of 19.7 to 500 ppm hydrogen,which is higher than that of Sn O₂.Furthermore,the nanocomposite material has a rapid response time of approximately 3 s and a recovery time of about 10 s,along with excellent performance parameters,such as high selectivity,repeatability,and long-term stability.These results suggest that this material has great potential as a sensitive and efficient tool for hydrogen detection.Compared to the single-component Sn O₂,the Cd Sn1:1 nanocomposite has higher electron mobility,optimized Fermi energy level,and abundant surface oxygen absorption,which are the primary reasons for its increased sensitivity to hydrogen.The key points of this work are as follows:1)the Cd O/Sn O₂ heterogeneous composites which are more sensitive to hydrogen have been prepared;2)Cd Sn1:1 nanocomposite exhibits the highest response and the fast response-recovery rate with great application advantages;3)the structure-activity relationship between Cd Sn1:1 composite and hydrogen sensing performance is clarified.