Preparation And Physical Properties Of Two-dimensional Transition Metal Sulfide (TMD) And Its Heterostructure

Since 2004,graphene has received great attention due to its excellent mechanical and electrical properties.However,due to its own zero band gap,the development of graphene in the fields of optics and optoelectronics has been limited.With the development of the times,more and more two-dimensional materials come into people’s sight.Transition metal sulfides（TMDs）are one of the representative ones,which have many physical properties that graphene does not have.At present,the research on TMDs materials has found that they have a good prospect in electronic and photoelectric devices,biomedical detection,catalysis and other fields.Based on the controllable preparation of TMDs two-dimensional atomic crystal materials and their van der Waals heterostructures,this thesis focuses on the vapor phase growth of MoS₂ two-dimensional atomic crystal materials,and then prepares two-dimensional vertical heterostructures and alloys based on single-layer TMDs materials.Finally,in-depth research on their basic characteristics has been carried out,and some valuable and instructive results have been obtained.The main contents are summarized as follows:（1）By the combination of magnetron sputtering and chemical vapor deposition（CVD）methods, large-scale and high-quality triangular MoS₂ flakes can be obtained on the Si O₂/Si substrate, supplying the experimental guidance for the fabrication of 2D TMDs heterostructures.（2）The preparation of Mo_1-xW_xS₂ alloy with adjustable composition range was realized by the sulfurization of sputtered metal Mo⊥W film.The composition of the alloy was further verified based on the optical performance characterization of the system,and its growth mechanism was preliminarily established for reasonable research and explanation.（3）By alternately using Mo（or W）foil and WO₃（or MoO₃）powder as precursors,two,three and four layers of 2D-TMD van der Waals heterostructures,including 1L-MoS₂/1L-WS₂、 1L-WS₂/1L-MoS₂、1L-MoS₂/2L-WS₂、2L-MoS₂/2L-WS₂ and 3L-MoS₂/1L-WS₂,were obtained under two different routes using one-step CVD method.These special multilayer vertical heterostructures were comprehensively evaluated by optical microscopy（OM）, atomic force microscopy（AFM）,Raman and photoluminescence（PL） spectroscopy/mapping.Finally,based on the influence of evaporation temperature on the concentration of Mo/W atoms in the vapor and the influence of growth temperature on the growth rate of Mo-S and W-S,a possible mechanism for the preparation of multilayer van der Waals heterostructures was proposed.