Synthesis And Photoelectric Properties Of Rhenium-based Chalcogenides And Their Composites

In 2004,the discovery of the graphene shocked the academic circle.Since then,two-dimensional materials represented by graphene have attracted the attention of a large number of scholars.However,it is unsatisfied to apply graphene to the photoelectric devices because it has no band gap.Through continuous exploration,scientists have discovered other 2D materials with unique optoelectronic properties,such as Rhenium-based chalcogenides in transition metal dichalcogenides(TMDs).It is a kind of new materials of the family of two-dimensional TMDs materials,which has the distorted1T structure and the extremely low symmetry of the lattice structure.Thus,these properties make it has the anisotropic optical and electrical properties,interlayer decoupling and the layer number of dependencies.Hence,this kind of material holds great potential for photoelectric device application because of their novel characteristic.And the material provided a new possibility for the preparation of the self-powered photodetector with high permanence.In this paper,ReS₂/Si heterojunction photodetector and Ag-ReS_2(1-x)Se_2xSchottky junction photodetector were designed and constructed on the basics of the controllable preparation of large-area and high-quality ReS₂nanosheets and ReS_2(1-x)Se_2xporous films.The main research contents of this paper are as follows:(1)Under different experimental conditions,ReS₂nanosheet films were epitaxial grown by Tellurium powder(Te)-assisted CVD method.Using this method,we had prepared large-area and high-quality ReS₂nanosheet films without Tellurium powder impurities.Through the characterization of several samples,we systematically explored the influence of Rhenium Tellurium ratio,temperature and other factors on the growth of the samples.The best experimental conditions for the preparation of the thin film was obtained.In addition,the Hall Effect test was carried out on the sample.It was found that the film was the n-type semiconductor and the surface carrier concentration and mobility were5.603×10⁸cm^-2and 4.304 cm²V^-1s^-1.(2)The ReS₂/Si heterojunction photodetector with high quality interface was constructed by directly growing the ReS₂nanosheet film on the etched Si/SiO₂window substrate.The photoelectric response of the device from the visible band to the near infrared band was tested.Under zero bias,the response of the device in the near infrared band of 980 nm was the best,and the light ratio was up to 1.6×10³,which was consistent with the band gap theory of this material.Moreover,the device had fast response with a rise time of about 5?s and a fall time of about 26?s at 638 nm.(3)A series of large and continuous ReS_2(1-x)Se_2xfilms with different components were synthesized by selenization of ReS₂nanosheet films grown on Silicon wafers.By characterizing the samples of different components,we found that the large-area and continuous ReS_2(1-x)Se_2xthin film synthesized by this method owned the porous structure constructed by the nanosheets.Not only was the lattice quality high,but the Re,S,and Se elements were uniformly distributed throughout the sample.(4)Ag-ReS_2(1-x)Se_2xSchottky junction photodetector were designed and constructed by PVD method coating Ag electrode on Ag-ReS_2(1-x)Se_2xthin film material.The optoelectronic properties of different compositions of Ag-ReS_2(1-x)Se_2xfilms of the devices were systematically investigated.The investigation results found that the photodetector based on the ReS_0.18Se_1.82film had the strongest photocurrent,so the optoelectronic properties of the device under this composition were tested in depth.The test results show that the responsivity,light on/off ratio,specific detectivity and response/recovery time of the device are 121.9 m A/W,6.4×10³,5.27×10¹²Jones,30ms/60ms at 365nm band and room temperature with zero bias.At the same time,the device also has a good response for the visible band and has the best response in the 450nm band,the light on/off ratio,responsivity,and specific detection rate are 2.1×10⁴,69.3m A/W,and 2.4×10¹²Jones,respectively.