Theoretical Study On Electronic Structure And Capacitance Of ZnO/Graphyne Heterostructures

Graphyne,graphene-like monolayer zinc oxide(ZnO)and other two-dimensional nanomaterials have received widespread attention from researchers because of their unique electronic structure and wide application.The emergence of two-dimensional materials' van der Waals heterostructures has broadened its application in nanoelectronics and optoelectronics.Against this background,the first-principles calculation method based on density functional theory is used to analyze the electronic structure of monolayer graphyne,monolayer ZnO and ZnO/Graphyne heterostructures in this paper.The application of ZnO/Graphyne heterostructures in the field of nanocapacitors is explored as well.The main research contents and conclusions of the paper are as follows:Firstly,a theoretical model of monolayer ZnO and ?,?,?-phase graphyne are constructed,and its geometric structure optimization and energy band structure analysis were performed.The results show that the conduction band and the valence band of the monolayer ZnO are located at the defect sites of the Brillouin ? point and belong to the direct transition energy band structure.The bandgap is 4.076 e V;the ?-and ?-phase graphynes are all zero band gaps.The conduction band and valence band tops of the ? phase graphyne are all located at the M point of the Brillouin zone,and the band gap value is 0.452 e V.Secondly,the heterostructures of ZnO/?-Graphyne,ZnO/?-Graphyne and ZnO/?-Graphyne with different stacking configurations are constructed by van der Waals forces.The Structural system stability,band structure,and capacitance characteristics of heterogeneity under external electric field are systematically studied..The research indicates that:(1)The binding energies of the ZnO/Graphyne heterostructures with different stacking configurations are all negative,and the binding energy of the system increases with the increase of the external electric field.,which show that the external electric field contributes to the stable formation of ZnO/Graphyne heterostructures.(2)The external electric field can effectively regulate the bandgap width of the ZnO/Graphyne heterostructure system.After the positive and negative electric fields are applied to the heterostructure system,the bandgap widths of ZnO/?-Graphyne and ZnO/?-Graphyne heterostructures monotonously increase with the increase of the electric field strength,but different in growth rate of the band gaps under the effect of positive and negative electric fields..This is because the spontaneous polarization in the ZnO/?-Graphyne and ZnO/?-Graphyne heterostructures make the bandgap width have different responses to positive and negative electric fields.However,for ZnO/?-Graphyne heterostructure systems,the positive and negative electric fields have different effects on the regulation of their bandgap.Under the positive electric field,the bandgap of ZnO/?-Graphyne heterostructure decreases with the increase of the forward electric field strength;under the negative electric field,the bandgap of the system increases with the increase of the negative electric field strength.(3)A large amount of charges are stored in the upper and lower layers due to the charge transfer between the ZnO layer and the graphyne layer of their layered stacking of ZnO/Graphyne heterostructures The ZnO/?-graphyne has a specific capacitance of 4~69 F/g,the ZnO/?-Graphyne has a specific capacitance of 5~81 F/g,and the ZnO/?-Graphyne has a specific capacitance of 4 ~ 74 F/g.This indicates that the ZnO/Graphyne heterostructure system has potential applications in nanocapacitors,which allowing proper charge and energy storage.