Based On Chemical Vapor Deposition Method To Tun The Structure Of Transition Metal Dichalcogenides And Explore Its Applications

Since graphene was successfully prepared in 2004,the development of two-dimensional（2D）materials has been in full swing.At present,the 2D material family has been very large,and it is still in the hot development stage.2D materials have many unique properties in the fields of electricity,optics,heat,and mechanics,and have played a role in promoting the development of catalysis,energy,integrated circuits,and quantum communications.However,the original 2D material with fixed performance has begun to appear to be unable to meet the versatile emerging applications.Therefore,the optimization of the performance of 2D materials is crucial in multifunctional devices.A lot of research shows that the structure regulation of 2D materials will be one of the most effective ways to achieve controllable performance modulation.However,there are still many problems and challenges.Therefore,it is necessary to further optimize the existing structural modulation strategies or propose new strategies.Firstly,this paper summarizes the significance,methods and challenges of the current structural modulation of 2D material.Then,aiming at the fractal structure and disassembly direction,which are seldom studied at present,based on chemical vapor deposition（CVD）,a feasible control scheme was designed,and the relevant experimental research was carried out.The main contents and results are as follows:（1）Through the CVD method,the number of branches of the 2D material and its extension direction can be adjusted.Firstly,based on the attachment-limited CVD method,1T’-WTe₂flakes with different branches were obtained.With the high mass transfer rate of diffusion and large precursor flux,the obtained 1T’-WTe₂ takes the meta symmetry which maintains the C_2v symmetry and expands along the sixfold axes（The angle between different branches is～60°or～120°）.Then,combined with the experiment and density functional theory（DFT）calculation,its edge-induced mechanism is explained.Finally,based on electrical testing,the meta symmetry of1T’-WTe₂ exhibits similar resistances for different channels and the nodes would not hinder the electron transport.The introduction of meta symmetry can make 1T’-WTe₂more suitable for electronics,and can inspire the novel strategies to improve the structural diversity of 2D materials.（2）Based on the CVD method and the catalysis of Te,the disassembly of 2D vertical heterstructures was achieved.Firstly,100%stacked Re S₂/WS₂ was prepared based on the CVD method.Then,using Te as the catalyst to weaken the van der Waals force between the layers of Re S₂/WS₂,and the assembly of Re S₂/WS₂ was realized based on CVD methods,and the monomer WS₂ and Re S₂were obtained.Secondly,based on various in-situ characterization results,combined with DFT calculation,the disassembly mechanism of Re S₂/WS₂ is described.Premises of the disassembly reaction are that:（1）Te atoms can play a"recognition"role in the selected 2D vertical heterojunction;（2）Combined with Te,the interlayer spacing of 2D vertical heterojunction will be greatly increased and the interlayer van der Waals force will be weaken.In addition,the disassembly strategy can be extended to other 2D vertical heterojunction,such as WS₂/G,which indicates that the disassembly method is universal.In summary,this method has great potential for editing and erasing 2D materials as device channels.