Theoretical Study On The Optoeletric Properties Of Silicether-based Van Der Waals Heterostructures

The successful preparation of graphene has proved that two-dimensional materials can exist stably at normal temperature,which has attracted extensive attention.Due to the unique structure and properties of two-dimensional materials,it is considered that two-dimensional materials can be applied to the future electronic and optoelectronic fields.With the continuous deepening of modern scientific and technological research,researchers have found that heterostructure composed of two two-dimensional materials can further improve the performance of a single material,and the heterostructure have unique optical and electronic properties.Therefore,the exploration of two-dimensional heterostructure formed by the superposition of two or several two-dimensional materials has become a research hotspot in the field of materials.In this paper,the first-principles calculation method is used by Materials Studio,a material simulation software,to simulate the structure and photoelectric properties of the silicether/graphether heterostructure,the silicether/h-BN heterostructure and the silicether/silicene heterostructure.Details are as follows:(1)In the first work,the electronic and optical properties of monolayer silicether and graphether and the silicether/graphether heterojunction formed by stacking the two materials are calculated based on the first principles.The effects of biaxial strain and applied electric field on silicether/graphether are investigated.The results show that the indirect band gap of the heterostructure is 0.63 e V,which is smaller than that of the monolayer silicether and graphether.By adjusting the biaxial strain and electric field intensity,the band gap of silicether/graphether heterostructure can be changed.Especially,the heterostructure changes from indirect band gap to direct band gap under compression strain,which is beneficial to their applications in sensitive optoelectronic devices.The absorption coefficient of silicether/graphether heterostructure shows a strong peak in the ultraviolet region,and the maximum absorption coefficient reaches 1.7×10⁵ cm^-1at 110 nm.Compared with the monolayer silicether and graphether,the light absorption coefficient of the heterostructure is significantly enhanced in the range of 80-170 nm.The results show that silicether/graphether heterostructure has an outstanding optical absorption in the ultraviolet region.This work may provide a novel material with potential application prospect for nanodevices.(2)In the second work,the silicether/h-BN heterojunction is designed and three structures are predicted successfully.The most stable stacking configuration and the best layer spacing were found by considering 12 stacking modes.Under this stacking,the three structures are all stable configurations.It is found that the heterostructure formed by the combination of the average lattice constants of silicether and h-BN is direct band gaps,while the other two cases are indirect band gaps.The bottom of conduction band and top of valence band of the three structures are mainly contributed by the silicether layer.In addition,the differential charge density indicates that no distinct charge transfer is found between the layers of the heterojunction.By comparing the band structure of monolayer silicether under strain regulation,it is found that the interaction between the layers of silicether/h-BN can cause the lattice to produce stress,which can effectively adjust the band structure of silicether.The structure of fixed boron nitride has the most obvious regulatory effect.This study shows that the band structure of silicether can be changed in a directional way at the atomic level,which has certain significance for guiding experimental work.(3)Finally,we predict the silicether/silicene heterojunction and calculate its electronic and optical properties.The results show that the silicether/silicene heterostructure is a new two-dimensional material.At the Dirac point near the Fermi energy level,the band gap opening range of the silicether/silicene heterojunction with different stacking modes in the silicene is 18-31me V.Due to the interaction interface distance,when the interlayer spacing of the heterostructure with stacking mode IV is 2.71(?),the binding energy is the lowest.In addition,the band gap opening of the silicether/silicene heterostructure can be adjusted by applying an external electric field.The calculated results show that the electric field can adjust the band gap from 0 e V to 0.184e V.As the distance between layers is modulated,the band gap changes both directly and indirectly.The optical absorption spectra shows that the silicether/silicene heterostructure exhibits stronger light absorption capacity in the range of ultraviolet to infrared light compared with monolayer silicether and silicene,and the intensity peak appeared in the ultraviolet light region,as high as1.23×10⁵ cm^-1.These studies indicate that the silicether/silicene heterojunction has certain application value in the future micro optoelectronic devices,solar cells and other fields.The silicether/silicene heterojunction may provide a new two-dimensional material for the application of nanometer devices.