Preparation Of MoS₂ Films By Vapor Liquid Solid Reaction With Ternary Oxide And Its Properties

Transition metal disulfide is a typical two-dimensional material.Compared with graphene,this material has an intrinsic band gap and it is widely used in electronic devices and photoelectric fields.Molybdenum disulfide(MoS₂)is one of the most promising transition metal disulfide with on/off current ratio and higher carrier mobility,which is suitable for the next generation of transistors.At the same time,when the number of layers of molybdenum disulfide decreases from block to monolayer,its band gap changes from indirect to direct,which changes its optical properties.Some achievements have been made in the theoretical calculation and experimental test of molybdenum disulfide films,but there are still many problems in the preparation of molybdenum disulfide with good crystallinity by chemical vapor deposition.In this paper,Na₂MoO₄ is mainly used as molybdenum source to prepare MoS₂.By changing the experimental parameters of chemical vapor deposition,large size and high quality molybdenum disulphide films were prepared by changing the experimental parameters of chemical vapor deposition.The quality and morphology of the film was characterized by optical microscope,scanning electron microscope,atomic force microscope and so on.The growth mechanism of the film was discussed.In order to apply molybdenum disulfide in more fields,we tested and analyzed the properties of molybdenum disulfide films under different environments.(1)The experiment mainly used Na₂MoO₄ and Na Cl as the precursor.By exploring five factors affecting the growth of monolayer MoS₂ crystal:growth temperature,growth time,amount of molybdenum source,the gas flow velocity and amount of sodium chloride.The best growth conditions of monolayer MoS₂ crystal prepared by CVD method were found.Through experimental comparison,the results show that the samples prepared under the optimal growth conditions are monolayer MoS₂ crystals,with a size of about 40?m.(2)The molybdenum disulfide film samples were characterized by laser Raman spectrometer,scanning electron microscope,atomic force microscope,and X-ray photoelectron spectrometer to obtain information on the crystallinity,morphology and product composition of the film.Through the analysis,we know that the gaseous precursor will deposit on the substrate surface,which forms the liquid.A part of the liquid will react to form the molybdenum disulfide nucleus.At the same time,the liquid will evaporate again.This subtle process makes the MoS₂ grow into a monolayer structure,which is also an important factor in forming the sag morphology.(3)To explore the changes of optical properties of molybdenum disulfide films under different environments:in the experiment of changing temperature,the two vibration summits of MoS₂ redshift with the increase of temperature.The peak of photoluminescence will also move in the direction of longer wavelength as the temperature increases.When the Angle of incident light is changed,the intensity of vibration peak will change periodically.When the molybdenum disulfide film is placed in an external electric field,the peak intensity of photoluminescence increases with the increase of the field intensity.