Width And Layer-number Controllable Synthesis And Characterzation Of WS₂-WSe₂ Lateral Heterostructure

Due to quantum size effects and edge effects,one-dimensional materials（1D）exhibit many different properties compared with two-dimensional（2D）nanosheets.In recent years,the heterostructures composed of one-dimensional and two-dimensional nanomaterials have attracted extensive attention due to their excellent electrical and physical properties.The hybid dimensional heterostructure not only exhibits the properties of two-dimensional materials,but also possess the properties of one-dimensional materials.However,previous studies on 2D/1D heterostructure mainly focus on vertical heterostructures.There are still few reports on 2D/1D lateral heterostructures.2D transition metal disulfide（TMDs）has received great attention in recent years due to their unique layer-number-dependent electronic and optoelectronic properties.These unique properties make TMDs materials play an important role in the field of electronic and optoelectronic devices.In addition,the heterojunction constructed by different TMDs materials has become a hot research topic in recent years.However,most of the reports on lateral TMDs heterostructure are based on monolayer materials,and the synthesis of 2D lateral TMDs heterostructure with bilayers or monolayer/bilayer mixstructures are very scarce at present.Therefore,it is necessary to develop a method to synthesize lateral heterostructure with different width and layers.In the first part of this paper,2D/2D and 2D/1D WS₂/WSe₂ lateral heterostructures were synthesized on Si O₂/Si substrates by the method of bidirectional gas chemical vapor deposition（CVD）,which accurately controlled the width of epitaxial heterojstructures by controlling the flow direction and growth time of carrier gas.Scanning electron microscopy（SEM）and atomic force microscopy（AFM）images show that the width of epitaxial WSe₂ ranges from 11 nm to 4μm by precisely controlling the growth time,and the 2D/1D heterojunction interface was clear and smooth.This study provides a new method for the preparation of 1D nanoribbons and opens up a way for the further study of the physical and chemical properties of 2D/1D lateral heterostructures.In the second part of this paper,the Se/W ratio on WSe₂ surface is controlled by introducing the pre-annealing process,and five kinds of WS₂-WSe₂ lateral heterostructures with different layers are synthesized.Their morphological characteristics,optical properties and atomic structures are studied.The relationship between Se/W ratio and layers of WSe₂ is also explained by DFT.The lateral heterostructure platform is greatly broadened,which lays a foundation for its application in the field of electronics and optoelectronics.