Manufacture And Performances Of Ultraviolet Photodetector Based On SnO₂ Nano-particles

The detection of ultraviolet?UV?light plays an important role in the fields of radiation monitoring,biochemical analysis,astronomy and missile launching,and there are more and more demands for high-performance UV detectors.Among various UV detectors,the photomultiplier tube is bulky and requires high power source;detecting speed of heat detector is too slow and the response of it is independent of wavelength.Semiconductor detector has a small volume,simple device structure and low in manufacturing cost.In addition,it can use the photoelectric effect of semiconductors to realize rapid response to UV light and detection of tiny signals,what make it promissing in UV detectors.SnO₂ And ZnO are suitable candidates of semiconductors for UV detectors manufacture because of their wide band gap?3.6 eV and 3.3 eV,respectively?and high electron mobility.Furthermore,the combination of them will form type II energy band structure,which is beneficial to separating photogenerated electron-hole.This study will investigate the synthesis of SnO₂ and ZnO-SnO₂ heterostructure and the application of them in UV detector.First,SnO₂ nanoparticles were prepared on the ITO substrate by magnetron sputtering and liquid deposition.Its morphology,chemical elements and crystals was analyzed by SEM,EDS and XRD.The experimental results show that the prepared sample contains Sn and O elements,and its morphology is a special octahedral nanoparticles structure.The diffraction peak energy of the XRD image can index to the SnO₂ tetragonal crystal.In addition,the formation mechanism of SnO₂ octahedral structure was explored.Secondly,ZnO nanoarrays were grown on the surface of SnO₂ octahedral nanoparticles by magnetron sputtering method and hydrothermal method to construct ZnO-SnO₂ heterojunction composite structure materials.The sample of ZnO-SnO₂ was characterized by SEM,EDS,TEM,XRD,XPS.The study found that the morphology of the ZnO-SnO₂ heterostructure was hedgehog-like structure which was composed of SnO₂ octahedral block and ZnO nanorods.Sn and Zn elements were distributed in octahedral block and nanorods structures,respectively.Then the formation mechanism of ZnO-SnO₂ hedgehog-like structure was analyzed by observing the evolution process of it.Finally,UV detector were prepared by using the synthesized SnO₂ octahedral nanoparticles and ZnO-SnO₂ hedgehog-like heterostructure as the materials for UV light detecting,and the detecting performance for UV light of the devices were tested under 365 nm simulated source of UV light.The results show that both devices are visible-blind and can respond to UV light.In addition,the prepared devices can work under zero bias,indicating that they has self-powered characteristics.Multiple tests show that the photogenerated current of the prepared UV detectors can steadily reach the same maximum with the irradiation of UV light,indicating they have cyclic stability.Compared with SnO₂ UV detector,ZnO-SnO₂ hedgehog heterostructure UV detector has higher photoresponse current.The study of detection mechanism shows that the performance improvement of ZnO-SnO₂ detector can attribute to the complex surface morphology and type ? energy band structure.