First Principles Study On Properties Of Cr-Substituted Materials Based On Two-Dimensional Silicon Carbide

Two dimensional semiconductor materials have been widely concerned and studied for their superior properties.Based on the first principles of density functional theory,the effects of Cr substituting Si and C atoms on the electronic structure,magnetic and optical properties of two-dimensional silicon carbide were studied by using the material system of graphene structure with different proportions of Cr substituting Si and C atoms.At the same time,the effects of Cr and Al atoms substituting Si and C atoms in two-dimensional SiC in different ways on the properties of the material system are calculated and analyzed.The conclusions are as follows:1.In the Cr substituted material system,the structure of Cr substituted Si atomic material system is regular,and the structure of Cr substituted C atomic material system is distorted,and the distortion increases with the increase of Cr substituted proportion.In 6.25%Cr and Al co-substituting system,Cr and Al co-substituting Si atomic material system,and the material system composed of Cr substituting Si atom and Al substituting C atomic material system are relatively regular.2.The results show that the energy band structure and electronic density of states change from semiconductors to alloy semi metals with the increase of Cr substitution ratio.The 6.25%Cr substitution Si atomic material system shows semiconductors,and the 12.5%,25%and 75%Cr substitution Si atomic material system changes to alloy semi metals;In the Cr substituted C atomic material system,6.25%and 12.5%Cr substituted C atomic material system show semiconductor properties;25%Cr,Al co-substituting system,Cr and Al co substituting Si atomic material system,respectively,Cr substituting Si atom and Al substituting C atom system,all show semiconductor properties.3.The results show that the materials with different proportions of Cr substituting Si atomic material system have magnetism.The magnetic distance of Si atom with different proportion of Cr displacement increases with the increase of displacement ratio,and it is linear.When Cr and Al are co-substituted,Cr and Al substituting Si,Cr substituting Si and Al substituting C atomic material system have magnetism.The results of spin polarized charge density and spin polarized electron state density analysis show that the magnetic properties of the system mainly come from Cr atoms.4.With the increase of the substitution ratio,the absorption edge of the material system with Cr substituting Si atoms in different proportions will be red-shifted,In the low energy range,the absorption peak value increases with the increase of substitution ratio,and the static dielectric constant,static refractive index and static reflectivity increase with the increase of substitution ratio.Both Cr and Al co-substitution materials can absorb lower energy photons,and the absorption edge moves to the lower energy band,which widens the absorption band of the material system.