Study On The Electronic Structure And Optical Properties Of Blue Phosphorene/MoS₂ (topological Phase) Van Der Waals Heterojunctio

Topological materials are new quantum states of matter with topological electronic structures that have been discovered in recent years and whose novel quantum effects at the macroscopic scale may revolutionise materials science,spintronics and computer science.The structural diversity of the two-dimensional transition metal sulphides MX₂（M for Mo,W,X for S,Te）endows these materials with many novel physical properties,such as the discovery of topological states in Mo S₂,Mo Te₂,WS₂,WTe₂,etc.These discoveries have made MX₂materials a hot topic in current condensed matter physics and materials science research.Among them,Mo S₂has high carrier mobility,excellent optoelectronic properties and a variety of phase structures.The 2H phase Mo S₂is a direct bandgap semiconductor,and the1T’phase and 2M phase Mo S₂are considered to have a topological structure.In this thesis,the electronic structure and optical properties of H-Mo S₂,T’-Mo S₂and2M-Mo S₂are comparatively analysed using the first nature principle based on density generalization,and the differences in their electronic structure and optical properties are analysed by using two-dimensional T’-Mo S₂and 2M-Mo S₂to construct van der Waals heterojunctions with blue phosphorene（Blue P）respectively.The effect of the applied stress on the electronic structure and optical properties of the heterojunctions was thus observed,and the main studies are as follows:1.Theoretical calculations of the electronic structures and optical properties of H-Mo S₂,T’-Mo S₂and 2M-Mo S₂show that due to the existence of energy band inversion in the topological energy band structures of both T’-Mo S₂and 2M-Mo S₂,the interband correlation and the overlap of wave functions in the conduction and valence bands are enhanced,which in turn leads to an enhanced photocurrent response and the optical response frequency extends to the mid-infrared and terahertz range.The optical properties of both are superior to those of H-Mo S₂.2.Blue P/T’-Mo S₂and Blue P/2M-Mo S₂van der Waals heterojunctions were constructed to study their electronic structure and optical properties,as well as the effect of applied stress on them.The results showed that the topological properties of T’-Mo S₂and 2M-Mo S₂were preserved after the construction of heterojunctions with Blue P,and the optical absorption coefficients of two-dimensional T’-Mo S₂and2M-Mo S₂were 17.52 and 27.5,respectively,while the optical absorption coefficients of Blue P/T’-Mo S₂and Blue P/2M-Mo S₂van der Waals heterojunctions were 34.01 and39.37,respectively.The applied stress has a significant modulating effect on the van der Waals heterojunction,resulting in stronger light absorption in the terahertz and mid-infrared wavelengths,and the modulating effect of compressive stress is more significant than that of tensile stress.The results greatly enrich the topological phases of Mo S₂and provide a reference for the design and application of high-performance photodetector devices based on Mo S₂topological phases,while Blue P/T’-Mo S₂and Blue P/2M-Mo S₂van der Waals heterojunctions show good applications in the fields of mid-infrared and terahertz semiconductor materials and optoelectronic devices.