Study On Preparation And Nonlinear Optical Properties Of Two-dimensional MoS₂/Bi₂Te₃ Heterostructure

With the further in-depth research on two-dimensional materials,a single type of two-dimensional material cannot be well adapted to diverse application requirements due to its own shortcomings.Therefore,the controlled stacking of different two-dimensional(2D)atomic layers to form heterostructures has a great prospect in significantly optimizing the optical properties of 2D materials and broadening their applications fields.In the dissertation,two-dimensional molybdenum disulfide(MoS₂)was grown by an optimizing chemical vapor deposition(Chemical Vapor Deposition,CVD)method,and two-dimensional bismuth telluride(Bi₂Te₃)nanoparticles prepared by an optimizing solvothermal method were spin-coated on it.The two-dimensional MoS₂/Bi₂Te₃heterostructure with high crystallinity and optical quality was successfully constructed.Based on the built micro Z scan and pump probe measurement technology,the dissertation systematically studied the nonlinear optical properties of two-dimensional MoS₂,two-dimensional Bi₂Te₃nanosheets and two-dimensional MoS₂/Bi₂Te₃heterostructures,and explored the influence of the morphology and layer number of MoS₂on the carrier dynamics process of the MoS₂/Bi₂Te₃heterostructure itself and its structure.The dissertation mainly included the following three contents,1.The preparation of two-dimensional and the nonlinear optical properties of MoS₂were investigated.Based on the CVD method,the Mo O_xobtained by electrochemically oxidizing the Mo foil was used as the precursor.The reaction temperature and the sulfur flow temperature had been further optimized to realize the high crystallinity of the 1L(Layer,L)MoS₂film and the 1L,2L,3L,and 4L MoS₂flakes.Comparing the carrier dynamics test results,it was found that the 1L MoS₂flake had the shortest relaxation time(?800 fs).The results indicated that the 1L MoS₂flake with more surface defects were beneficial to the photogenerated carrier process.The results also revealed the 1L MoS₂flake had strong third-order nonlinear saturation absorption coefficient.The work provided potential materials for high-performance saturated absorbers.2.The preparation of two-dimensional and the nonlinear optical properties of Bi₂Te₃were studied.The high crystallinity hexagonal Bi₂Te₃nanosheets with the thickness of about 10 nm were prepared by adjusting the experimental parameters of the solvothermal experiment process.The nonlinear optics and carrier dynamics tests showed that the Bi₂Te₃nanosheet had good nonlinear saturation absorption characteristics and fast carrier relaxation time with 450 fs.The results also indicated that Bi₂Te₃nanosheets can be used as potential materials for ultrafast saturable absorbers.3.The construction of two-dimensional and the nonlinear optical performance of MoS₂/Bi₂Te₃heterostructure were discussed.Based on the physical spin coating method,the prepared two-dimensional Bi₂Te₃nanosheet suspension was diluted to a certain extent.The high-quality two-dimensional MoS₂/Bi₂Te₃heterostructures were successfully constructed by spin coating the two-dimensional Bi₂Te₃on the two-dimensional MoS₂sheet by the homogenizer.According to the built-up micro-zone Z-scan and pump probe device,the dissertation positioned and studied the nonlinear optical performance of the two-dimensional MoS₂/Bi₂Te₃heterostructure,and compared it with the performance of the corresponding single component.The results showed that due to the charge transfer from the 1L MoS₂to the two-dimensional Bi₂Te₃,the 1L MoS₂/Bi₂Te₃heterostructure had excellent nonlinear saturated absorption coefficient and ultra-short carrier lifetime(?440 fs).The results also revealed that the 1L MoS₂/Bi₂Te₃heterostructure can be used as a saturable absorber for ultrashort pulse lasers.This work paves the way for the design of new tunable two-dimensional photonic materials that combine the optical advantages of different two-dimensional materials.