Preparation Of Monolayer MoS₂ Films And Research On Interface Contact Characteristics Of Devices

In recent years,two-dimensional nanomaterials have attracted much attention due to their ultra-thin thickness and immune properties to short channel effects.As the representative of two-dimensional materials,MoS₂is widely used in field effect transistors,sensors,catalysts and many other fields due to its tunable band gap,high mobility and good mechanical flexibility.However,in order to achieve the industrial application of MoS₂,the controllable preparation of large-area,high-quality monolayer MoS₂films is the important prerequisite,and the optimization of the contact characteristics of the device interface is also the indispensable.This paper conducts in-depth research and discussion on these two aspects,and the specific content is as follows:Controlled fabrication and growth mechanism of large-area monolayer MoS₂films.In the experiment,the monolayer MoS₂films were synthesized by chemical vapor deposition（CVD）method to explore the influence of different gas flow rates on the thickness and size of the films.At the same time,gas flow gradient model was constructed to analyze the growth mechanism combined with the experimental phenomenon.It is found that the gas flow rate is the key factor affecting the final morphology and thickness of the film.When the gas phase transport rate of the inert gas and the chemical reaction rate of the precursor are matched during the film growth,the controlled growth of the monolayer MoS₂film is beneficial.When the gas flow rate is set to 40 sccm,the triangle size of MoS₂can reach 160μm.The quality of the film is analyzed by OM,Raman,AFM,XPS,HRTEM and other characterization methods,which proves the ultra-thin thickness and high crystal quality of the prepared monolayer MoS₂film.Research on Contact characteristics and mechanism of single layer MoS₂field effect transistor.In this paper,the MoS₂backgate FETs were designed and constructed by using traditional micro/nano fabrication technology,and the contact characteristics between MoS₂and electrode interface and the reasons for the reduction of contact resistance were deeply explored.In the experiment,the influence of different dielectric layer materials on the contact characteristics was compared,and the thickness of Al₂O₃dielectric layer was optimized and compared.The results show that when the Al₂O₃dielectric layer thickness is 0.8 nm,the device exhibits an ultra-low contact resistance of 1.3 kΩ·μm,an ultra-low Schotky barrier height of 27 me V,an excellent switching ratio of～10⁸,and large increase in the current and mobility of the devices.Then,the lattice and band structures of the Al₂O₃/MoS₂film were calculated and analyzed by first principles calculation,and the possible mechanism was explored by combining calculation and experiment.The results show that the ultra-thin Al₂O₃interface layer could not only reduce the height of the Schottky barrier,but also alleviate the Fermi level pinning phenomenon at the interface.It can also be used as the cover to protect the channel material from air and moisture.The reduced contact resistance of single-layer MoS₂FET has facilitated the widespread use of low-power,high-performance electronic devices.