Photoluminescence Photoelectric Properties Of MoS₂ And Modification By Ga Doping

With the advent of the"post-Moore era",traditional semiconductor materials have been difficult to meet people’s growing demand for information materials.The next generation of new semiconductor materials will be the key to breaking the post-Moore era.In the process of searching for a new generation of low-dimensional semiconductor materials,two-dimensional layered semiconductor materials have received widespread attention from scientists at home and abroad.Among them,transition metal dichalcogenides（TMDCs）are particularly outstanding in 2D layered semiconductor materials,which have atomic-level ultrathin thickness,continuously tunable band gap and high carrier mobility.It has become one of the representatives of the new generation of semiconductor functional materials in the post-Moore era.The potential applications of TMDCs have focused considerable research on the growth of high-quality,large-area materials.Among the numerous synthetic strategies,chemical vapor deposition（CVD）has attracted great interest due to its scalability and controllability.However,the intrinsic doping problem caused by uncontrollable defect formation during growth seriously degrades the performance of CVD-grown TMDC materials,which remains unsolved.Fortunately,the existence of a large number of defects can also facilitate the introduction of dopants,and substitution doping is the preferred modification method for TMDCs due to its high stability and controllability.In view of this,this paper focuses on the performance regulation of MoS₂monolayer nanosheets,and modulates the optical properties of MoS₂monolayer nanosheets based on Ga atom doping,and reveals the connection between its morphology evolution and defect repair.The main research results are summarized as follows:（1）Monolayer MoS₂ nanosheets were synthesized on a silicon wafer substrate by CVD,and the Atomic Force Microscopy（AFM）,Raman spectroscopy（Raman）,and high-resolution transmission electron microscopy（High-Resolution Transmission Electron Microscopy）were used.Electron Microscopy,HR-STEM),Photoluminescence（PL）and other systems were used to characterize the thickness,crystal structure and luminescence properties of the obtained materials.The effect of growth parameters on the morphology and size of monolayer MoS₂was investigated by optical microscopy,and the preparation of high-density and large-scale monolayer MoS₂was achieved by adjusting the growth parameters.And the intrinsic n-type semiconductor field effect transistor with high switching ratio and high carrier mobility was prepared based on MoS₂synthesized by CVD.By repeating and analyzing the synthesis experiments for many times,a morphology evolution model of MoS₂nanosheets based on S:Mo atomic ratio was established under S-rich conditions,the evolution process of MoS₂with different shapes was described,and three shapes of MoS₂nanosheets were obtained by photoluminescence spectroscopy.The corresponding relationship between the appearance and its internal defects:the defects of truncated triangular and nearly triangular MoS₂are concentrated in the central area,while the defect distribution of regular triangular MoS₂is relatively random and uniform.（2）Ga-doped MoS₂nanosheets were proposed and studied.Based on CVD method,Ga₂O₃was used as dopant to prepare Ga-doped MoS₂nanosheets.The HR-STEM characterization results show that Ga atoms replace the sites of Mo atoms and S atoms in the MoS₂monolayer nanosheet lattice,and most of them enter the sites of S atoms.X-ray photoelectron spectroscopy（XPS）and PL characterization further proved that the Ga atomic doping is P-type electronic doping.Based on the peak fitting results of the temperature-dependent photoluminescence spectra of pure MoS₂and Ga-doped MoS₂monolayer nanosheets,we believe that Ga doping alleviates the many-body effect and electrostatic shielding,allowing more triplets to be converted into the excitons enhance the luminescence properties of the material,achieving two orders of magnitude enhancement of photoluminescence intensity and nearly one order of magnitude enhancement of carrier lifetime.On this basis,the use of Ga doping to repair sulfur vacancies in monolayer MoS₂is proposed and realized.The repair mechanism is that Ga doping can preferentially enter the S vacancy-enriched region in the sample to complete the repair work.This inference was further confirmed in HR-STEM analysis.Combined with the results of the simulation calculations,it can be concluded that this is a facile defect repair strategy based on the CVD one-step synthesis method,which can significantly enhance the material’s performance by selectively repairing defects in monolayer MoS₂through the controllable doping of Ga atoms.Photoluminescence intensity.This strategy of selectively repairing defects in monolayer MoS₂by gallium doping to achieve significant enhancement of photoluminescence may provide a promising method for the regulation of optoelectronic properties of 2D materials.