Synthesis Of Two-Dimensional MoSe₂ And Its Optical Properties

As an emerging two-dimensional(2D)material,molybdenum diselenide(MoSe2)has attracted great attention due to its unique band structure and excellent mechanical properties.Studies have shown that it has great application potential in the field of optoelectronics.However,the current preparation method is so immature that its practical application is still difficult to achieve.In view of this,the chemical vapor deposition(CVD)synthesis method is studied in detail in this paper,and the auxiliary growth of MoSe2 and the controllable preparation of its shape,size and number of layers are discussed.As described next:1.Considering the growth conditions,substrate and precursor,the possibility of assisting the growth of MoSe2 was explored through the control variable method,focusing on:(1)Effect of H2 on the growth of monolayer MoSe2:H2 promotes the reduction and selenization reactions while reducing excess intermediates or by-products.Finally,the single layer of MoSe2 is obviously easier to grow on the substrate.(2)Effect of substrate on the growth of monolayer MoSe2:The obliquely face-down SiO2/Si substrate makes the growth of single-layer MoSe2 simpler and more uniform.Because it increases the surface gas flow rate of the substrate,thereby reducing the thickness of the boundary layer and increasing the deposition rate of the film.(3)Effect of NaCl on the growth of monolayer MoSe2:NaCl accelerates the sublimation of MoO3 and the rate of selenization,so the monolayer MoSe2 grown on the substrate is significantly more dense.A variety of characterization techniques such as atomic force microscopy and photoluminescence spectroscopy are performed on the grown samples,demonstrating that it is a strictly single layer with good uniformity,reasonable stoichiometry,and excellent luminous efficiency.2.Controllable growth of shape,size and number of layers of MoSe2.Based on the auxiliary growth conditions,the controllable preparation of MoSe2 is further studied.The shape control of MoSe2 can be controlled by adjusting the H2 content and growth time,and the mechanism is discussed.The size of MoSe2 can be controlled by adjusting the gas flow rate and the amount of NaCl.a triangular single-crystal single crystal of about 120 ?m,a hexagonal single-layer single crystal of about 150 ?m,and a single-layer continuous film having a lateral size of about 300 ?m can be obtained.Finally,the number of layers of MoSe2 is achieved by adjusting the vertical distance between the substrate and MoO3/NaCl control.Figure 54,table 3,references 56.