Investigation Of Gas Sensor Based On Nano-structure P-type Metal Oxide Semiconductor

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic,commercial and industrial applications,which become one of the current research hotspots for its many advantages such as low cost,easy production,compact size and high detection precision.In recent years,it is possible that the realization of high-performance gas sensors due to some progress of new nano-functional materials research has been achieved,and some of the devices based on metal oxide semiconductor(MOS)in terms of gas detection have reached the level of commercial applications.However,gas sensors based on semiconductor metal oxide nanomaterials are also faced with problems such as low concentration sensitivity is not high enough,selectivity is poor and response-recovery time is long.The work of this thesis is for the development of high-performance gas sensor.The three-dimensional nickel oxide nano-material with high specific surface area was designed and the gas-sensitive characteristics of the sensor based on the nanometer material were studied and the performance of the device is optimized by the method of noble metal surface modification and n-type nano-doping,and it is expected to obtain the gas sensor with excellent performance.In this thesis,the development history and research status of gas sensors are reviewed,and the research results of n-type sensitive materials are summarized.The parameters affecting the sensitivity of the devices are also analyzed.Based on the sensitive theory of n-type MOS material,the gas-sensing principle of p-type MOS material is expounded in detail.NiO nano-materials with flower-like structure were fabricated by electrochemical deposition method and subsequent oxidation treatment.The gas sensing performance of the sensor based on this material was measured systematically.The results show that the sensor exhibits a high sensitivity to low concentrations of formaldehyde and ethanol at relatively low temperatures,meanwhile,the response-recovery time is shorter for both gases.The surface modification of NiO nanomaterials prepared by hydrothermal method was carried out by noble metal Ag nanospheres.The sensitivity measurement of gas sensors based on pure NiO and Ag-NiO were carried out,meanwhile,the results of sensitivity measurement were comparative analys is.It was found that the sensitivity of the Ag-NiO devices was greatly improved.Compared with device based on pure NiO,it is almost twice the sensitivity of device by Ag surface modification.The ZnO nanomaterials with flower-like structure were prepared under low temperature condition,and renewable and environmentally friendly plant extracts was used as reductants in this process,which were used in the preparation of NiO-ZnO heterojunction composites.The sensitivity measurement of gas sensors based on heterogeneous heterojunction composites with different components were carried,meanwhile,the results of sensitivity measurement were comparative analysis.It was found that the heterojunction composite device doped with 3% ZnO has better sensitivity than other devices.At the same time,the response-recovery time of ZnO-doped devices is obviously shortened,and that the response-recovery time does not change with the ZnO doping amount.