Preparation Of MoS₂ Thin Film By CVD Method And Its Property Detection

With the increasing research progress of two-dimensional(2D)materials,the application potential of 2D materials in many fields continues increase.As a new type of2D material,molybdenum disulfide(MoS₂)film has a broad application prospect in the fields of photo-electronic devices,flexible devices,catalysis,new energy,etc.based on its own unique properties.However,the applications of 2D MoS₂ thin film materials also faces many challenges.At present,it is still impossible to industrially prepare large area 2D MoS₂ thin films at low cost,especially for the preparation of high quality monolayer MoS₂films,destruction problems during transfer of 2D MoS₂ films,etc.In this paper,from the point of view of the growth mechanism of MoS₂ thin films,the effects of different factors on the preparation of MoS₂ thin films by chemical vapor deposition(CVD)method were investigated.Results showed that,with the extension of the holding time,the films began to"splice"into thin films,and finally nucleated on top of this film to grow bulk MoS₂ thin films.The carrier gas flow rate can affect the growth of MoS₂films and the best Argon flow rate is 75 sccm.The position of the molybdenum source affects the controllable growth of the MoS₂ film,and we can get monolayer MoS₂ thin film at a molybdenum source distance of 185 mm.By optimization of the process,a high-quality monolayer MoS₂ film was successfully grown on a sapphire substrate with the size of 4 cm×0.8 cm.The Raman spectral characteristic peak of the sample had a wavenumber difference of 19.28 cm^-1,the PL spectral characteristic peak was at 659.30 nm,and the electron transition energy of the sample was 1.88e V.At the same time,the surface energy assisted method was used to transfer the MoS₂film,and the difficulties and solutions of the transfer process were discussed.During the transfer process,the spin coating speed can affects the distribution of the Polystyrene(PS)film on the surface of the MoS₂ film.When the rotation speed is 3500 r/min,the PS film is well distributed on the surface of the MoS₂ film.Two-step heat treatment can reduce cracks formed during the transfer of MoS₂ thin films,and the characteristic peaks of Raman spectra of monolayer,triple-layer and bulk MoS₂ films before and after transfer are remain unchanged.The hydrogen evolution reaction(HER)properties of MoS₂ films with different layers and MoS₂ films with different crystallinity were studied.Under the same crystallinity as for monolayer MoS₂ film,bilayer and triple-layer MoS₂ films,the electrocatalytic performance of MoS₂ film is enhanced when the number of layers decreases.Under certain conditions,the electrocatalytic performance of MoS₂ films with the same number of layers increases with the decreasing of crystallinity.The work of this thesis perfects the 2D MoS₂ film growth theory,which will provide experimental guidance and theoretical reference for 2D preparation of TMDCs system.The surface energy assisted transfer method was used to successfully peel and transfer MoS₂films with different layers,which provided a feasible idea for the development of 2D MoS₂film transfer technology.It is proved that the hydrogen evolution performance of the 2D MoS₂ thin film after transfer is related to the number of MoS₂ layers and crystallinity.