Preparation And Study Of Porous Thin Film Semiconductor Gas Sensitive Materials And Gas Sensors

With the development of the Internet of Things and portable intelligent devices,the requirements for gas sensors are becoming higher and higher.Not only do they need good gas sensing properties,or the metal oxide gas sensing materials are modified by modulation structures or composite materials but the process and size also need to be compatible with integrated circuit technology,further standardization and miniaturization.This paper first analyzes the requirements of micro-heating plates for thin film gas sensors,and designs micro-heating plates prepared by MEMS process according to requirements.The finite element analysis software was used to parametrically model and simulate the temperature distribution of the heating plate,and the appropriate parameters were selected according to the simulation results of different heating electrode line width and line spacing.The preparation of the micro-heated plate was then carried out,and the similarities and differences between the simulation and the actual use temperature were tested.Subsequently,based on the micro-heated plate,polystyrene beads were used as a mask for magnetron sputtering,and then a tin oxide film having a porous surface was prepared and annealed.The surface morphology was then characterized by XRD,SEM and AFM.For the use of different diameters of polystyrene beads,different etching times,different sputtering thicknesses and whether or not to carry out the underlying tin dioxide sputtering four different process conditions,by testing the sample to 100ppm concentration of ethanol gas.The best gas-sensitive response belongs to the sample that for a 1?m-diameter pellet,which is subjected to an oxygen plasma etching for 450 s,and a layer of tin dioxide is first deposited in the interdigitated electrode region,so that a 100 nm thick porous gas-sensitive material is also formed inside the pore.The tin dioxide film sample has the best gas sensitivity characteristics,and the sensitivity reaches 4.1 at an operating temperature of 220°C,and has a fast response recovery speed and good repeatability.Thereafter,a 5nm metal oxide material was continuously prepared by electron beam evaporation without removing the PS bead mask to form a porous film heterojunction gas sensor having a bilayer structure.In this paper,NiO,WO₃,In₂O₃,CeO₂,TiO₂and ZnO were used to form a heterojunction with SnO₂,and they were characterized and tested.It was found that the NiO/SnO₂ porous film heterojunction structure constituting the PN junction has the best structure.The gas sensitivity characteristic was 9.6 for a 100 ppm ethanol at 220°C.The relevant sensitive mechanisms are explained.