| Benefit from the quantum confinement effect,interface interaction,interlayer coupling,and large specific surface area,two-dimensional semiconductor materials exhibit distinct superior properties compared to bulk materials.As a typical two-dimensional semiconductor material,MoS2 demonstrates tremendous potential in fields such as microelectronic devices and optoelectronic materials,and has been used in devices like transistors,photovoltaic cells,and sensors.In these applications,the interface between MoS2 and metal materials plays a crucial role,making the study of metal/MoS2 interfaces of utmost importance.The characteristics of these interfaces,such as their band structures and electron transport properties,can significantly influence the performance of the system.Understanding the structural evolution of metal/MoS2 interfaces contributes to optimizing and enhancing the overall efficiency and performance of MoS2-based devices.Gold is a common electrode material,while silver exhibits excellent conductivity.Therefore,this thesis designs and fabricates two heterostructure interfaces,gold/MoS2 and silver/MoS2,as model systems.Various analytical methods,including Raman spectroscopy,scanning electron microscopy(SEM),atomic force microscopy(AFM),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD),and transmission electron microscopy(TEM),were employed to investigate the interface interaction between metal and MoS2 at the atomic scale,as well as the relaxation process of the interface interaction with time in the presence of a substrate.The observation of strain relaxation at the metal/MoS2 interfaces over time reveals the influence of MoS2 layer number and substrate on the strain relaxation process at the interfaces.The research work is mainly divided into the following three parts:1,In this dissertation,a silver/MoS2 heterostructure is designed and fabricated.Raman spectroscopy is employed to characterize the modulation of the MoS2 phonon structure by the interface strain in the heterostructure.The relaxation process of the interface strain is traced,revealing that the rate of strain relaxation depends on the layer number of MoS2.Specifically,monolayer MoS2 exhibits the longest strain relaxation time,while thicker layers of MoS2 show faster strain relaxation.2,The influence of three common substrate materials,SiO2/Si,Al2O3,and mica,on the relaxation process of interface strain in silver/MoS2 heterostructures was systematically investigated.Lorentz curve fitting was employed to extract Raman peak information,and density functional theory(DFT)simulations using the Vienna Ab initio Simulation Package(VASP)were conducted to calculate the interface interaction between MoS2 and the substrates.A comparison with SiO2/Si and mica substrates reveals that the Al2O3 substrate exhibits stronger interface interaction with MoS2,resulting in strain pinning.3,Aberration-corrected transmission electron microscopy(TEM)was utilized to analyze the crystal structure,atomic arrangement,and their impact on interface strain in metal/MoS2 interfaces.The dependence of the structural evolution rate of Au nanoparticles(NPs)under electron beam irradiation on the layer number of MoS2,influenced by interlayer van der Waals forces,was explained.Due to the larger scattering cross-section of MoS2 atoms for inelastic collisions with high-energy electrons,there is a direct correlation between the increased movement speed of Au NPs under electron beam irradiation and the layer number of MoS2.This study provides a valuable reference for investigating interface strain,phonon vibration modes,and other aspects of heterostructure interfaces using Raman spectroscopy.It establishes a reliable experimental foundation for the precise construction and practical applications of metal/MoS2 heterostructure interfaces in the future. |
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