Theoretical Study On Structures And Electronic Properties Of Two-dimensional Materials PC₆N And BC₂P

Since the successful exfoliation of graphene in 2004,two-dimensional(2D)materials have attracted research interest because of their excellent properties.In past two decades,the types and application fields of 2D materials have developed rapidly.2D materials exhibit many unique properties that are different from three dimensional materials.Although two-dimensional semiconductor materials have outstanding advantages in the development of new optoelectronic devices,there is an urgent need to design new materials with high carrier mobility and high stability.More and more 2D materials predicted by theoretical calculation have been synthesized experimentally,which demonstrates the guiding significance of theoretical calculation to the research and development of new materials.The characteristics of strong covalent bonds and various coordination modes among the main group of non-metallic elements are conducive to stabilizing 2D materials and enriching structural types.At present,the research of such 2D materials is mainly focused on binary compounds.Studies have shown that increasing the variety of elements and varying chemical ratio is an effective way to obtain new materials with excellent properties.In this paper,the structure,stability and electronic properties of two kinds of ternary compound two-dimensional materials of phosphorus-carbon-nitrogen(P-C-N)and boron-carbon-phosphorus(B-C-P)are identified by the first principles structure search technique.The main research contents and conclusions of this paper are as follows:(1)Theoretical calculation identifies stable semiconducting PC₆N monolayer with a wide band gap and high carrier mobility.We combine first-principles calculations with structure prediction method to find stable structures of P-C-N compounds with various compositions,and identify a stable PC₆N monolayer.The stability of PC₆N monolayer in oxygen environment is demonstrated by molecular dynamics simulation in oxygen environment and calculation of the energy barrier required to cross from physical adsorption to chemical adsorption of oxygen.At the HSE06 level,the PC₆N monolayer is a semiconductor with a direct band gap of 2.56 e V,and we analyze the physical origin why PC₆N monolayer has a wide band gap.The hole mobility along the armchair can reach 10⁴cm²V^-1s^-1,which realizes the balance of wide band gap and high carrier mobility.At the same time,the absorption coefficient of PC₆N monolayer in ultraviolet region can reach 10⁵cm^-1,and there is almost no absorption in the visible region.These excellent properties indicate that the PC₆N monolayer can be a candidate for UV optoelectronic devices.(2)In the B-C-P system,theoretical calculations have found a BC₂P monolayer with semiconductor properties.The stability of the BC₂P monolayer is determined by phonon spectrum,cohesive energy,and molecular dynamics simulation.The BC₂P monolayer is an indirect band gap semiconductor with a band gap of 1.52 eV at the HSE06 level.The carrier mobility is calculated using the deformation potential theory,and the hole mobility reaches 800cm²V^-1s^-1 both armchair and zigzag direction.At the same time,the light absorption coefficient can reach 10⁵cm^-1 in the visible light region.The calculation of the band edge position shows that the band edge position of BC₂P can cross the redox potential of water.Therefore,the BC₂P monolayer is promising as a candidate photocatalyst for photocatalytic water splitting.