Study On The Regulation Of Electronic Structure Properties Of Two-dimensional Heterojunction Based On C₂N

In 2004,two scientists at the University of Manchester,Ander Geim and Konstantin Novoselov,successfully discovered a monoatomic layer of graphite,graphene,from a mineral graphite using the“tear tape”method.This discovery opens the door to two-dimensional materials.Because the force between two atoms of graphene is very strong,graphene has many advantages.For example,high mechanical strength,good tensile properties,good electrical conductivity,good thermal conductivity and so on.Therefore,it has a strong role in military,folding electronic equipment,batteries,computer chips,etc.Since then,more and more graphene-like and other two-dimensional（2D）materials have been discovered experimentally and theoretically,including hexagonal boron nitride（h-BN）monolayers,transitionmetal dichalcogenides（TMDs）,Elemental ene,and even C₂N.However,no single 2D material has all of the desired properties.For example,the zero band gap of graphene limits its applications in high-performance electronic devices.h-BN is difficult to synthesize and has a large band gap and high insulation properties.Different structures of chalcogenides have a greater influence,black phosphorene is unstable in the air.Researchers have found that forming vd W heterojunctions can overcome the limitations of single-layered materials and exhibit novel properties.Recently,Javeed Mahmood et al.successfully synthesized a graphene-like layerd C₂N monolayer using a simple wet chemical reaction method,It has a huge specific surface area and a suitable band gap.Unlike graphene,it possessed a uniform honeycomb nitrogen lattice with 2/3 of the honeycomb vacant sites filled by C₆hexagons（the rest of the honeycomb vacant sites could be viewed as vacant of C₆）,Thus,it possess a huge s editable properties.Based on these excellent characteristics,this paper uses the first-principles calculation method to study the electronic structural properties of C₂N/α-Te and C₂N/In₂SSe（In₂STe,In₂Se Te）heterojunction and effectively regulate the band gap through interlayer coupling,external electric field and effect of the biaxial strain,so that the heterojunction can be used to an excellent extension in the field of solar cells and photocatalytic water splitting.The main research contents of the paper are as follows:（1）By constructing a C₂N/α-Te van der Waals heterojunction,and calculating the mismatch and considering different stacking methods,we found that C₂N/α-Te has good thermodynamic stability.The C₂N/α-Te vd W heterojunction had an intrinsic type-II band alignment,whose indirect band gap value was 1.01 e V.And by applying vertical stress and external electric field,the band gap can be effectively modulated to1.16 and 1.14 e V（HSE06 calculation）,respectively.A type-II to type-I transition occurred under an external electric field.Interestingly,the C₂N/α-Te vd W heterojunction possessed high optical absorption strength（～10⁵）and broad spectrum width（ultraviolet to near-infrared region）,and strengthen the absorption intensity of C₂N by about 3 times.（2）C₂N/In₂SSe（In₂STe,In₂Se Te）van der Waals heterojunctions were constructed by considering the lattice fit and stability,and it was found that C₂N/In₂SSe and C₂N/In₂STe have intrinsic type-I band alignment before stress compression control and is an indirect band gap.The C₂N/In₂Se Te heterojunction has an intrinsic type-II band alignment and is a direct band gap.After the stress compression control,the C₂N/In₂SSe and C₂N/In₂STe heterojunctions changed from type-I to type-II,and the indirect band gap changed to direct band gap.The C₂N/In₂Se Te heterojunction maintained the type-II alignment and was a direct band gap.The band edge position is suitable for photocatalytic water decomposition during strain compression control.In addition,the optical absorption and width of the three van der Waals heterojunctions have been significantly improved in ultraviolet and near-infrared light after adjustment.