PtSe₂ And WSe₂/BP Van Der Waals Heterostructures Theory Study

After the successful stripping of graphene,a two-dimensional（2D）crystal composed of carbon atoms,its unique physical and chemical properties have become the focus of scientific and industrial attention,which has a wide range of applications in semiconductor optoelectronic devices and nanoelectronics.With the development of science and technology,a single 2D material can no longer meet the requirements of scientists for semiconductor.The van der Waals heterostructures,which are formed by stacking two or more 2D structures,solving some defects of a single 2D material and obtaining fascinating excellent performance,which has a good application prospect in the fields of nanodevices,photocatalysis and photodetectors.In this paper,the geometric structure and photoelectric properties of PtSe₂/HfS₂ and WSe₂/BP heterostructures were investigated by first principles calculation of Vienna ab initio simulation package（VASP）.In addition,the changes of the heterostructure band structure under applied electric field and strain are emphatically investigated,obtaining the research results for reference.The structural stability and photoelectric properties of monolayers of PtSe₂,HfS₂ and PtSe₂/HfS₂ heterostructure are studied in detail.It is worth mentioning that heterostructure formation shows higher light absorption intensity.By applying an external electric field,the band structure of the heterostructure can be changed significantly,but the Type-II band alignment remains all the time,and the transition from semiconductor to metal occurs when the critical electric field is reached.In addition,the PtSe₂/HfS₂ heterostructure changes from Type-II to Type-I band alignment under different biaxial strains,while the heterostructure keeps the Type-II band alignment under uniaxial strains.The heterostructure changes from semiconductor to metal after applying greater strain.More interestingly,the heterostructure is sensitive to compressive strain but insensitive to tensile strain,which provides theoretical guidance for photoelectric devices in specific environments.These results indicate that PtSe₂/HfS₂heterostructure will be widely used in photodetectors and nanodevices.Besides,monolayer WSe₂ and monolayer BP have similar lattice constants.Given good structural stability and appropriate lattice misalignment rate,we constructed high-quality WSe₂/BP van der Waals heterostructure.The calculation results show that a direct band gap of0.78 e V and Type-II band arrangement are formed on the WSe₂/BP heterogeneous bilayer interface,which is conducive to effective separation of photoelectrons and holes and showed a wide absorption spectrum in visible light region.Furthermore,the effects of different stacking angles and defects on the stability of heterogeneous structures and photoelectric properties are also verified.It is worth mentioning that the WSe₂/BP heterostructure alignment change from Type-II to Type-I and then Type-II band alignment under different electric fields.The transformation of semiconductors to metal can also be observed under stronger electric fields.At the same time,the band gap is effectively regulated by the biaxial strain.Therefore,these properties enable WSe₂/BP heterostructure to have a promising application prospect in future light detection.