High Performance ZnO Nanowire Network Ultraviolet Sensor Modified By SnO₂ Nanoparticles

In the information age,especially with the rapid development of the internet of things,sensors have been paid more and more attention as the basic equipment to obtain information.Being a member of the family of sensors,the ultraviolet（UV）sensors have important applications in areas such as UV communication,environmental monitoring,flame detection and missile warning.Zinc oxide（ZnO）is a wide band gap semiconductor with a direct band gap of 3.37 eV at room temperature and the exciton binding energy is up to 60 meV.Thus,ZnO is insensitive to visible light.Besides,ZnO also possesses the merits of low cost and good thermal stability.The research into ZnO based UV sensors have made great progress in recent years,making high-performance UV sensors with high sensitivity,rapid response and stable performance a research hotspot.With the development of UV sensors,researchers have designed and fabricated a ZnO nanowire network UV sensor with a sensitivity of 1.98×10⁸ when illuminated by365 nm UV light of 1 mW/cm².However,the response/recovery speed of the device is slow,with the response/recovery time being up to 100 seconds or more,which seriously affects the application of ZnO nanowire network UV sensor.Surface functionalization has been studied by the researchers as a powerful method for improving the performance of ZnO UV sensors through a series of work.In this thesis,a local SnO₂/ZnO heterojunction was constructed by modifying tin oxide（SnO₂）nanoparticles on the surface of ZnO nanowires,through which the devices’dark current was greatly reduced,and sensitivity and response/recovery speed were dramatically improved.Besides,the performance of the ZnO nanowire network UV sensor was regulated by controlling the amount of SnO₂ nanoparticles.The dark current of the device was reduced from 1.76×10^-12 A to 4.20×10^-15 A,the maximum sensitivity of the device was 7.29×10⁸,and the response/recovery time of the device was reduced to 2.5/7.5 s,respectively.In addition,with the increase of the amount of SnO₂ modifying nanoparticles,a device with the shortest response time of72 ms and the shortest recovery time of 27 ms was obtained,which had the sensitivity of 6.76×10⁵.The photocurrent of ZnO nanowire network sensor decreased obviously under continuous illumination.The experimental results show that the annealing treatment was an effective method to improve the photocurrent stability of the device.Then,the device with response time of 72 ms,recovery time of 27 ms and sensitivity of6.76×10⁵ was annealed to improve the stability of photocurrent.Finally,an UV sensor with a response time of 690 ms,a recovery time of 450 ms and a sensitivity of2.26×10⁶ was obtained.This device exhibited the sensitivity as high as 348 to even very weak UV light with the intensity of 20 nW/cm².