Growth Of SnO₂ Microwires By CVD And Its Device Application In Ultraviolet Photodetector

Wide band gap oxide semiconductors have many potential applications in the field of optoelectronic technology,such as solar cells,photodetectors,gas sensors,and lightemitting diodes.Tin oxide?SnO₂?,as a member of a wide band gap semiconductor,has a direct band gap semiconductor material of IV-VI semiconductor with a band gap of 3.7-4.0 e V and high carrier mobility?250 cm2V-1S-1?,which make it a promise candidate for application in the field of ultraviolet detection corresponding the wavelength range of 280-320 nm,called UVB,which has been used in the fields of life medicine,plant growth,flame monitoring,etc.SnO₂ thin films with high crystal quality have been realized by MBE,MOCVD,and PLD.SnO₂ nanostructures have also been prepared by Hydrothermal method.However,the condition of the low temperature preparing process result in too many defects in this materials.In this thesis,we introduce CVD method to grow SnO₂ materials.A SnO₂ MWs with length of 5-8 mm and 3-6 micrometer of diameter have been obtained for the first time.Based on these SnO₂ MWs,we design and prepared the heterojunction UV detectors,and achieved the following innovative research results:?1?Using chemical vapor deposition?CVD?method,by mixing high-purity graphite powder and high-purity SnO₂ powder in a 1: 1 ratio as the reaction source,silicon wafer as substrate,and argon?Ar?as protective gas Oxygen?O2?was used as the reaction gas in a high-temperature tube furnace,and SnO₂ MWs were successfully prepared.The MWs are clearly visible to the naked eye and have a length of 5 mm to 8 mm.Through X-ray diffraction?XRD?testing,it can be determined that the SnO₂ MWs prepared by us are rutile-phase tin dioxide,and the crystal quality is high.Scanning electron microscope?SEM?images show that the appearance of tin dioxide MWs is a quadrangular prism structure,and the surface is very smooth.?2?A single SnO₂ MW photodetector and a SnO₂-based photodetector modified with CH3NH3 Pb Br3 surface were successfully prepared.A high-quality P-type CH3NH3 Pb Br3 perovskite material was successfully prepared by chemical synthesis method,and then it was dropped on the surface of SnO₂ MWs,and CH3NH3 Pb Br3 was evenly dispersed on the surface of the MWs.Compared with a single SnO₂ MW device,the modified SnO₂ MW detector shows a higher spectral responsivity,and more importantly,the response time is shortened from a few hundred seconds to less than 1s.The results of this experiment provide a very good choice for the development of highperformance SnO₂-based photodetectors.?3?Using commercial organic conductive polymer PEDOT: PSS combined with a single SnO₂ MW and using metal indium as an electrode,a PEDOT: PSS / SnO₂ heterojunction self-powered photodetector was successfully prepared.At 0 V bias,the peak response is at 300 nm,and the peak response is 20 m A / W.Under 5 V reverse bias,the peak responsivity can reach 20 A / W.In addition,the response speed of this detector is significantly higher than that of a single SnO₂-based photodetector,and the response time is shortened to 0.2 s.