Electronic Structure Of Two-dimensional Graphyne Van Der Waals Heterostructures

Two-dimensional（2D）monolayer graphyne（γ-GY）is a novel all-carbon material with rich carbon chemical bonds,excellent thermoelectric properties and semiconductor properties.γ-GY has potential applications in the energy field of catalysis,hydrogen storage,lithium ion batteries and seawater desalination due to the unique structure and physical properties.2D van der Waals heterostructures based onγ-GY and 2D nonmagnetic（or magnetic）materials can also show novel physical properties.The electronic properties of 2D heterostructures can also be adjusted by vertical electric field and biaxial strains,which provides a important theoretical foundation for their designs and applications in nanoelectronic devices.In this dissertation,the electronic structure and Rashba splitting of 2Dγ-GY/WSe Te heterostructures,tunable electronic structure and magnetic properties of2Dγ-GY/VI₃ heterostructures and the electronic structure and magnetic characteristics of 2Dγ-GY/Janus V₂I₃Br₃ heterostructures are studied systematically based on density functional theory.The electronic structure of 2Dγ-GY/WSe Te heterostructures is calculated.Inγ-GY/WSe Te heterostructures,the contact types can be affected by different stacking patterns（γ-GY/Te WSe heterostructures possess Ohmic contact,whileγ-GY/Se WTe heterostructures have Schottky contact）.At a vertical electric field,the Schottky contact ofγ-GY/Se WTe heterostructure turns into Ohmic contact.The electric dipole moment and Rashba spin splitting of Janus WSe Te monolayer are increased by coveringγ-GY layer.Meanwhile,the Rashba spin splitting ofγ-GY/WSe Te heterostructure can be further tailored by electric field.The electronic structure and magnetic properties of 2Dγ-GY/VI₃heterostructures are calculated.The results show that semiconductor or half-metallic characteristic of VI₃ monolayer inγ-GY/VI₃ heterostructures can be shown due to the difference stacking patterns.The perpendicular magnetic anisotropy（PMA）of VI₃monolayer is enhanced by coveringγ-GY layer.Biaxial strain and interlayer distance can modulate the electronic structure and magnetic properties ofγ-GY/VI₃heterostructure.Meanwhile,the interlayer interaction ofγ-GY/VI₃ heterostructure can be enhanced by decreasing the interlayer distance,which further promotes the charge transfer.The electronic structure of 2Dγ-GY/Janus V₂I₃Br₃（γ-GY/V₂I₃Br₃）heterostructures are investigated.By combingγ-GY layer,Janus V₂I₃Br₃ monolayer can shows the half-metallic characteristic.Compared with the pristine Janus V₂I₃Br₃monolayer,the PMA ofγ-GY/V₂I₃Br₃ heterostructures is enhanced.At a compressive strain of-4%,Janus V₂I₃Br₃ monolayer inγ-GY/V₂I₃Br₃ heterostructure realizes the transition from magnetic half-metallic to magnetic metal state.Moreover,the PMA ofγ-GY/V₂I₃Br₃ heterostructure can be further enhanced by applying compressive strain.