Research On The Design And Performance Of Zinc Oxide Nanorod Gas Sensor Sensitized With Quantum Dots

Metal oxide semiconductor gas sensors have the advantages of high sensitivity,low manufacturing cost,fast response speed,long service life,etc.,which have been widely used in various fields such as environmental monitoring,industrial manufacturing,personal safety and medical diagnosis.Zn O has a wide band gap of 3.37 e V,a large exciton binding energy of 60 me V,high electron mobility,and excellent chemical and thermal stability.It is one of the most widely used metal oxide gas-sensitive materials.However,the traditional Zn O gas sensor has to work at a temperature higher than 300?,generally.It is difficult to recover and has low sensitivity at room temperature,which limits its development in the direction of low power consumption and flexibility.Studies at home and abroad have proved that light irradiance can effectively replace thermal excitation to improve the sensitivity and response recovery speed of Zn O at room temperature.However,due to the wide band gap,Zn O can only absorb and utilize ultraviolet light.In this paper,based on Zn O nanorod array as gas-sensing materials,the FDTD simulation of electromagnetic field distribution and absorption spectrum of Zn O/Pb S architecture was performed by using Pb S quantum dots with narrow and adjustable band gap as light-absorbing material.A nitrogen dioxide sensitive film covering the broad spectrum of ultraviolet-visible-near infrared light was prepared.The gas-sensing performance of the sensor under light illumination was optimized,and the light-enhanced gas-sensing mechanism was explored.First,the structure simulations of pure Zn O nanorod array and Zn O nanorod array sensitized with Pb S quantum dots were performed by FDTD solutions software.The electromagnetic field distribution and absorption spectrum under different light wavelengths were simulated and analyzed.The results show that the sensitization of Pb S quantum dots can extend the absorption spectrum from the ultraviolet region to the visible-near infrared region.Based on the simulation results,the Zn O/Pb S gas sensor was prepared.Zn O seed layer was first prepared by magnetron sputtering to solve the problem of lattice mismatch.The Zn O nanorod array was prepared by chemical bath deposition method based on the seed layer.The NO₂ gas sensing performance of the thin film resistive sensor at room temperature was studied.Further,Pb S quantum dots were used to sensitize Zn O nanorod arrays.Tests at room temperature found that the response of the sensitized structure to NO₂ increased from41 to 98 under light compared to pure Zn O nanorod array,and the response/recovery time was reduced from 78/196 seconds to 42/56 seconds.Finally,Pb S quantum dots with different band gap widths were prepared by controlled synthesis process.The room-temperature gas-sensing characteristics of the sensors using Pb S with different band gap widths under illumination were studied.As the band gap width of Pb S quantum dots becomes smaller,the sensor can absorb infrared light with a larger wavelength(from 950 nm to 1200 nm),and the response to NO₂ can be improved by about two times under a larger spectral range.However,as the band gap of quantum dots decreases,the conduction band bottom of quantum dots is lower than the conduction band energy level of Zn O.There may be a certain electron barrier at the heterojunction interface,which hinders the effective injection of photogenerated electrons into Zn O.Therefore,the improvement of gas-sensing performance under the light of same wavelength is gradually reduced.