| A two-dimensional material is a new type of crystalline material with the thickness of a single or a few atomic layers.There are strong chemical bonds between atoms in the two-dimensional layer,and the layers are usually stacked together by weak van der Waals forces.As an important member of the family of twodimensional materials,molybdenum disulfide has attracted much attention in recent years due to its excellent properties in mechanics,thermal,optics and electronicis.Monolayer molybdenum disulfide is a sandwich-like structure consisting of two layers of sulfur atoms with one layer of molybdenum atoms sandwiched in between.The thickness is about 0.6 nanometers.It is reported that single layer molybdenum disulfide is an excellent material for fabrication of low power mos Field Effect Transistor with excellent mobility and current switching ratio at room temperature.Molybdenum disulfide also has good thermal stability and chemical inertia,and its mechanical properties are stable and can tolerate very high deformation.It also shows great application prospects in the field of flexible electronics.In addition,the direct optical band gap of single-layer molybdenum disulfide is about 1.8e V,which makes it have excellent photoelectric characteristics and can be predicted to have great potential in the future flexible photodetectors,solar cells and other aspects.The excellent properties of monolayer molybdenum disulfide make it possible for many future applications.However,at present,the preparation of large-area,high-quality monolayer molybdenum disulfide is still the most critical scientific problem.This paper focuses on the key issue of the preparation of monolayer molybdenum disulfide films,and carries out the following research:1.Establishment of chemical vapor deposition system in three-temperature zone.In order to obtain high quality monolayer molybdenum disulfide film,considering the cost and stability,in this paper,we adopt the chemical vapor deposition method of slow growth,and design the tube furnace growth system in three temperature zone.The system is mainly composed of gas passage,one inch tube furnace,vacuum pump and tail gas treatment device.Considering the stability of the growth source,sulfur powder and molybdenum trioxide powder were used as the source and silicon as the substrate.During growth,sulfur powder,molybdenum trioxide and silicon wafers will be placed in three different temperature zones of quartz tube,and carrier gas will be introduced.The three temperature zone chemical vapor deposition system can effectively control the growth source temperature,deposition temperature,carrier gas flow rate,system pressure and substrate position during molybdenum disulfide growth.It lays the experimental foundation for obtaining cm continuous monolayer molybdenum disulfide film.2.Preparation of monolayer molybdenum disulfide film.We further explore the preparation principle and technology of monolayer molybdenum disulfide thin film by using three-temperature zone chemical vapor deposition system.By changing the temperature of the reaction to the quality of the source,source,deposition temperature,carrier gas flow rate and the substrate locations of substrate reaction in the process of changing growth source concentration and reaction temperature,reaction pressure,the realization of molybdenum disulfide nucleation grain size(20-1600 nm),grain density and film forming rate(10 to 40 min)effective regulation.3.High quality large area monolayer molybdenum disulfide film.Based on the previous work,a self-designed three-temperature zone chemical vapor deposition system was used to prepare monolayer molybdenum disulfide films on a centimeter-size silicon substrate.The obtained film is composed of polycrystalline molybdenum disulfide with a grain size of 1 micron and has a complete monolayer crystal structure and excellent optical properties.The surface of the film is clean and smooth,evenly covering the entire silicon substrate,without gaps,and at least the second layer.Through a series of characterization,it is shown that the large size monolayer molybdenum disulfide films grown have excellent quality and uniform distribution.It also solves the key scientific problem for the industrial application of molybdenum disulfide in the future. |
PDF Full Text Request