Research Of Gas Sensor Based On Heterojunction Composite Of CNT And Iron Oxide

In the field of gas sensors,Metal Oxide semiconductor?MOS,Metal Oxide Semiconductors?gas sensor has high sensitivity,adjustable selectivity,high reliability,and the characteristics of all solid state.It has been a hot research topic.However,because of the constantly improve the environmental standards and the use of the special environment on the performance of sensor,more stringent requirements are put forward.At present,although the research of semiconductor oxide gas sensor based on side-heater device has made great progress,it is still a major challenge to further enhance the sensitivity and selectivity and reduce the power consumption and the detection threshold.Against the above scientific problems,this work launches the research from two aspects.First,design and develop the microstructure device using MEMS?Micro – Electron-Mechanical System?technology to reduce the power consumption.Second,design and fabricate the high performance materials.We produced the CNT@Fe₂O₃ heterostructure composite gas sensing materials using liquid phase synthesis technology.The structural advantage of the composite material and the changed height of the heterojunction barrier under different atmosphere,were taken to enhance the sensor sensitivity.The concrete research content is as follows:In terms of the devices,we designed the MHP?Micro hot-plate?based on MEMS technology,and evaluated the influence of some factors on the temperature distribution of the MHP,such as the shape of the heating electrode,the silicon layer on the back of the MHP.Thus,we took the serpentine heating electrode,kept the silicon layer of 0.5 ?m,and the overall size of the device is 2 mm * 2 mm * 0.4 mm.After that,the MHP was fabricated through the MEMS technology.Then the actual performance was tested by an infrared thermal imager.The results showed that the thermal filed of the MHP distributed uniformly,the high temperature zone was mainly concentrated in the suspension film,and the heating efficiency of the MHP was about 4.69 ° C/m W.In terms of building highly sensitive materials,we combined with the excellent Fe₂O₃ gas-sensing properties and carbon nanotube?CNT?which has large specific surface area and high mechanical strength,to product the CNT@ heterostructure composite materials using simple liquid phase synthesis.Electron microscopy?sem?results show that the CNT@?-Fe₂O₃ is formed by assembling polycrystalline ?-Fe₂O₃ nanorods on CNT backbones.The structure had the length of several microns and the diameter of about 500 nm.Compared to the single ?-Fe₂O₃ nanorods,the CNT@?-Fe₂O₃ composite have the larger specific surface areas and adsorbs higher chemical oxygen.The measurement results show that compared to the ?-Fe₂O₃ nanorods,the CNT@?-Fe₂O₃ sensor showed an enhanced response to acetone with the higher response?35 to 100 ppm acetone at 225 ??,good selectivity,faster response and recovery time and good long-term stability.In addition,we fabricated the MHP gas sensor based on CNT@?-Fe₂O₃ heterogeneous composite.Compared to the side-heater device,its sensitivity and selectivity to acetone remain the same,but the power consumption at 225 ? for 44 m W,only about 1/10 of the side-heater device?460 mW?.