Research On The Controllable Growth And Rhenium Photoelectric Properties Of Twodimensional Rhenium Diselenide And Its Tungsten Doped Alloy

Since the discovery of graphene,two-dimensional materials become a hot spot in current research.As a member of the two-dimensional materials,transition metal chalcogenides（TMDs）make up for the zero band gap of graphene itself due to its adjustable band gap,higher carrier mobility and low electrocatalytic overpotential.Defects have great potential in the fields of data storage devices,energy conversion devices and laser light polarization devices,have attracted the attention of researchers.Different from the mainstream 2H phase Mo S₂ and WS₂,Re-based TMDs have twisted 1T structure,weak interlayer coupling and strong in-plane anisotropic optical properties.These characteristics can make Re-based TMDs material in polarized electrons devices and polarized optoelectronics have great application potential.Chemical vapor deposition（CVD）is considered to be the best method for preparing TMDs with a controllable number of layers,high quality and strong stability.However,Re-based TMDs are prone to out-of-plane anisotropic growth and uneven thickness due to weak interlayer coupling and twisted lattice junctions.It is difficult to grow high-quality,efficient and controllable Re-based TMDs materials by CVD.In view of the above problems,this paper designs a salt（Na Cl）assisted CVD growth system which uses Na Cl to promote the decomposition of ammonium perrhenate（NH₄Re O₄）into volatile Re₂O₇.The system promotes the decomposition of ammonium perrhenate（NH₄Re O₄）into volatile Re₂O₇ through Na Cl,which effectively increases the vapor pressure of the Re source and accelerates the reaction rate of the precursor vapor,increasing the growth rate of the ReSe₂ film,solve the problems of many by-products,low crystal lattice quality and low yield in the research.At the same time,a semi-closed reaction chamber is designed to make the precursor in the Si/Si O₂ substrate forms a vapor reflow,the reactant vapor fully reacts at the bottom of the substrate,and finally a high-quality,large-area single-layer ReSe₂ film is successfully prepared.Next,thickness,morphology and quality of the film are adjusted by changing the carrier gas flow,growth temperature,H₂ concentration in the carrier gas and the distance between the rhenium source and the selenium source,revealing the unique out-of-plane anisotropic growth mode of this type of material.Afterwards,through morphological characterization,spectrum analysis,composition analysis and other means,the characteristics of ReSe₂ film is systematically explored.Finally,field effect tube based on ReSe₂ film is constructed to study the electrical and photoelectric properties of ReSe₂ devices.On the basis of synthesizing high-quality ReSe₂ thin films,through the sodium chloride（Na Cl）assisted growth method,the same CVD process is used to prepare Re_xW_1-xSe₂ alloy thin films with adjustable bandgap.The different element groups are characterized by light mirror images.The changes in the morphology of the alloy films are analyzed.Raman spectroscopy and photoluminescence spectroscopy are used to characterize the optical changes of the alloy films with different layers and different element compositions,and the anisotropy of the alloy materials are studied.Through X-ray photoelectron energy Spectroscopy（XPS）confirmed the successful preparation of alloy films with different elemental compositions.Afterwards,the influence of a series of parameters on the growth results of alloy films are discussed.Finally,field effect transistor based on the Re_xW_1-xSe₂ alloy film is constructed,and the electrical and study optoelectronic properties of the alloy device under different element compositions.The results showe that the W-rich Re_0.11W_0.89Se₂ alloy device has lower contact resistance.The on-off ratio is 10³,the light response rate is as high as 38 m A/W and the light response speed is about 40 ms.These results prove the two-dimensional material alloying engineering can improve the electrical and optical properties of the material device.