Preparation Process And Gas-sensing Performance Of Metal Oxide Semiconductor Nanoarray-based Gas Sensor

With the advantages of stable physicochemical properties,simple preparation,low cost,and excellent performance,metal oxide semiconductor based gas sensors are currently the most studied and widely used gas sensors.With the continuous development of nanomaterial technology,the research focus of gas-sensitive materials has gradually changed from traditional bulk materials and thin-film materials to small-sized nanomaterials.In addition,micro gas sensor combined with MEMS technology presents a great research value and broad research prospect due to the advantages of miniaturization,integration,and portability.This thesis mainly studies metal oxide semiconductor gas sensors based on MEMS interdigital microelectrodes.The gas-sensitive material was on-chip synthesized on the surface of interdigitated electrodes.By means of doping with noble metal and preparing hybrid nanoarrays,the gas-sensing properties of the sensors to target gases were improved.The main research work of this thesis is as follows:Fabrication of Cr/Au interdigital electrodes and on-chip synthesis of SnO2 nanosheet arrays(NSAs).A lift-off process and pattern reversal technology were used to prepare Cr/Au interdigital electrodes on the surface of the silicon substrate.A simple chemical bath deposition(CBD)method was applied for the on-chip synthesis of the SnO2 nanosheet arrays on the interdigitated electrode.According to the results from morphological characterization,after an oil bath at 95°C for 8 h with subsequent an annealing at 400? for 2 h,SnO2 nanosheet arrays with a sheet thickness of less than 10 nm and a diameter of about 50-80 nm was successfully prepared.The ethanol-sensing performance of SnO2 nanosheet array-based sensor was briefly explored.Preparation of Pd-doped SnO2 nanosheet arrays for hydrogen sensor.By adjusting the concentration of Pd2+ions in the dopant solution,the effect of different doping concentrations on the morphology of the materials was studied.After doping process,PdO nanoparticles were formed on the surface of SnO2 nanosheets,and with the increase of doping concentration,the amount of PdO particles increased while the size of PdO particles became larger,and some of the PdO particles even began to agglomerate.At an operating temperature of 380?,by comparing the hydrogen sensing properties of devices with different doping concentrations,it was found that devices with a doping concentration of 0.05 M present the highest response to hydrogen(85.34%,60 ppm hydrogen).With the doping of Pd element,the hydrogen sensing properties of SnO2 were significantly improved.Preparation of 1D/2D ?-Fe2O3/SnO2 hybrid nanoarrays(HNAs)for acetone sensor.?-Fe2O3/SnO2 HNAs were prepared by a two-step CBD method,and a second chemical bath deposition(80? 1h)was carried out to synthesize ?-Fe2O3 nanorods(NRs).By adjusting the experimental parameters(the concentration of urea in the precursor solution and the reaction time),the optimal parameters for material synthesis was explored.By comparing the acetone gas-sensing performance of SnO2 NSAs,?-Fe2O3 NRs,and ?-Fe2O3/SnO2 HNAs,it can be concluded that the gas-sensing properties of ?-Fe2O3/SnO2 HNAs were effectively improved,showing effective response to acetone at sub-ppm level(3.25,0.4 ppm).