Study On Controllable Preparation And Physical Properties Of MoS₂

Molybdenum disulfide（MoS₂）,as the most representative material of two-dimensional transition metal chalcogenides,has attracted much attention due to its excellent physical and chemical properties in recent years.Meanwhile,the van der Waals heterojunction related to MoS₂ has become the focus of research in recent years because of its unique interfacial band structure.It is well known that material preparation is the basis of its performance research and application of large area,the preparation of large area MoS₂ and its related heterojunction so far has been a lot of progress（main）by chemical vapor deposition（CVD）method,but it is worth noting because the CVD growth process in a substance and physical field,the interaction of multiple parameters such as complex environment,therefore,MoS₂ and its related mechanism of the influence of preparation conditions on the structure of the heterojunction and change law is still not entirely clear,large area MoS₂ and related heterojunction controllable preparation still faces many challenges.In this paper,the low-pressure CVD method was used to realize the controllable preparation of centimeter-level monolayer MoS₂ films on the basis of the study of the growth mechanism of MoS₂,and further controllable preparation of single-layer,double-layer,three-layer and four-layer MoS₂ films with excellent homogenization,realizing the controllable number of layers of MoS₂.The effects of temperature,power and number of layers on the fluorescence properties of MoS₂ thin films were further studied.The results show that the monolith MoS₂ thin films have excellent photoluminescence properties at room temperature.With the increase of the number of layers,the band structure changes from direct band gap to indirect band gap,and the fluorescence power decreases.On the basis of the research on the controlled preparation of MoS₂ films,centimeter-level single-layer MoS₂/graphene heterojunction films,double-layer MoS₂/graphene heterojunction films,three-layer MoS₂/graphene heterojunction films and four-layer MoS₂/graphene heterojunction films have been realized,and the effective regulation of the number of MoS₂ layers in the MoS₂/graphene heterojunction films has been realized.The effects of temperature,laser power and layer number on the fluorescence properties of MoS₂ were further investigated,and the band structure at the interface of MoS₂/graphene heterojunction was revealed（electricity in MoS₂ was transferred to graphene through the interface）.At the same time,compared with single-layer,three-layer and four-layer MoS₂,double-layer MoS₂ has stronger electron transfer ability for graphene in MoS₂/graphene heterojunction structure.The research work in this thesis will not only be beneficial to the basic research of the photoelectric performance mechanism of MoS₂ and its van der Waals heterojunction,but also will promote the development of its application in new optoelectronic devices.