Gas Sensitivity Of Semiconductor Gas Sensitive Materials

With the rapid development of modern industries,toxic and hazardous gas pollution has become one of most serious issues.The gas sensor is generally composed of four parts:gas-sensitive materials,gas-sensing structure,signal conversion circuit and auxiliary power supply.The gas-sensitive materials is the core of gas sensor.Therefore,humans have been committed to finding high-performance sensitive materials.As a kind of gas detecting tool,which converted the information of gas composition and concentration to electrical or optical signal information,gas sensors gradually have drawn great attention.In this paper,CdS microspheres,Fe₂O₃/ZnO and NiO/ZnO heterostructures were prepared by solvothermal,hydrothermal and atomic layer deposition techniques and were used as gas-sensitive materials to explore their gas-sensing properties.Among the nanomaterials,metal oxide and sulfide semiconductor materials have become a hotspot materials with their excellent gas-sensing properties.The main research contents the following aspects:?1?The second chapter of the paper,cadmium sulfide?CdS?microparticles are prepared via an ionothermal route.The structure of the as-synthesized CdS microparticles is investigated by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.To investigate the sensing properties of the as-synthesized CdS microparticles,several gases are tested on the CdS sensor.The results show that the as-synthesized CdS microparticles have higher sensitivity towards NO than other gases?CH4,CO,H₂,H₂S and SO2?,indicating good selectivity for detecting NO.?2?The third chapter of the paper,we report a gas sensor for testing H₂S gas based on Fe₂O₃/ZnO heterostructure,which was synthesized using the atomic layer deposition?ALD?technique.Compared with the Fe₂O₃ nanosheet gas sensor and ZnO gas sensor,the Fe₂O₃/ZnO heterostructure gas sensors exhibits better sensing performance at the temperature ranging from 150? to 350 ?.In the environment of 100 ppm H₂S at 250 ?,the highest response of Fe₂O₃/ZnO heterostructure gas sensor,about 133.1,was obtained,which is approximately 15-fold as large as that of the Fe₂O₃ nanosheet gas sensor?about 8.7?.In addition,the response of Fe₂O₃/ZnO heterostructure gas sensor reached 21.7,11.3,4.9,6.7,3.6-100 ppm isopropanol,NO,acetone,ethanol,and methane in the same condition,respectively.These results also reveal that the Fe₂O₃/ZnO hetero-structure gas sensor exhibited the high selectivity.?3?In the fourth chapter of the paper,NiO/ZnO nanoplates were fabricated for gas sensors.Gas sensing characteristics toward ethanol,CO,H₂,H₂S,acetone,and 1,2-propanediol were measured,respectively.Our results show that the sensing performance is significantly improved in the NiO/ZnO nanoplate gas sensor as compared with the NiO gas sensor,which was ascribed to the decoration effect of ZnO nanoparticles on the surface.We also found that the NiO/ZnO nanoplate gas sensor exhibited higher sensitivity to ethanol gas than other gases?CO,H₂,H₂S,acetone,and 1,2-propanediol?at 400 ?,indicating good selectivity of ethanol sensing.