Research On Controllable Growth And Characteristics Of Two-dimensional Layered Rhenium Disulfide And Its Alloy

Re-based TMDs materials such as Rhenium disulfide?ReS₂?,as a new two-dimensional layered material,have great application prospects in the fields of electronic devices,photodetectors,and electrocatalytic hydrogen evolution due to their unique crystal structure,excellent optical and electrical properties.However,the distorted 1T structure and weak interlayer coupling of Re-based TMDs materials make them prone to anisotropic and out-of-plane growth.Therefore,there are still great challenges in preparing Re-based TMDs materials by chemical vapor deposition?CVD?.In view of these problems,we proposes a NaCl-assisted confined space CVD method in this thesis.This method can effectively solve the problems of uncontrollable growth of Re-based TMDs materials in shape and layer number,and realizes the controllable preparation of large-area,large-size,and high-quality monolayer ReS₂,ReS_2?1-x?Se_2x,Re_1-xMo_xS₂,and ReS₂/MoS₂ heterostructure films.The morphologies,elemental compositions,and optical properties of these films are systematically studied via a series of characterization methods.We also fabricate photodetectors based on these films to further study their optoelectronic properties.The main research contents of the paper are as follows.1.The NaCl-assisted confined space CVD method is utilized to grow large-area,large-size and high-quality monolayer Re-based TMDs materials on SiO₂/Si substrates.The NaCl can not only lower the melting point of Re source,but also effectively promote the formation of highly volatile oxide Re₂O₇.The confined space can give rise to relatively lower reactant concentration,relatively lower flow rate,and stable growth environment.These two key factors jointly promote the controllable preparation of large-size and high-quality monolayer films.We systematically study the structure,composition,and optical characteristics of the deposited ReS₂monolayer films.The key growth factors are adjusted to control the composition,shape,and layer number of the ReS₂ films.We also fabricate photodetectors based on these monolayer ReS₂ films and study their photoresponse performances.2.The monolayer ReS_2?1-x?Se_2x alloy films are successfully prepared by using the NaCl-assisted confined space CVD method,and the continuous control of the alloy composition is achieved by adjusting the S and Se ratio,and a series of characterization methods are used to prove that the grown thin films have good uniformity and high crystal quality.Both the shape and layer number can be effectively controlled by regulating growing temperature and carrier gas flow rate.The anisotropy of monolayer ReS_2?1-x?Se_2x films is carefully studied by angle-resolved polarized Raman spectroscopy.We also fabricate photodetectors based on monolayer ReS_2?1-x?Se_2xx films and systematically study their photoresponse performances.The results show that these photodetectors display good photoresponse to visible?447,532,and 637 nm?and near-infrared light?940 nm?.It is found that the increase in Se component will greatly reduce the response time of the corresponding alloy-based photodetector.In particular,the monolayer ReS_0.96Se_1.08 film based photodetector achieves the fastest photoresponse of 15 ms,which is significantly better than that of previously reported photodetectors based on ReS₂ or ReSe₂ films.3.Monolayer Re_1-xMo_xS₂ alloy films are also successfully prepared by the same method,and the layer number can be controlled by adjusting the carrier gas flow rate.These films are proved to possess good uniformity and high crystal quality in terms of morphology,elemental composition and optical characterizations.We also fabricate Re_1-xMo_xS₂ film based photodetectors and study their photoresponse performances.The ReS₂/MoS₂ vertical heterojunction films are successfully prepared by one-step method.Further structure and optical characterizations indicate the high quality of the synthesized heterojunction films.