First Principles Study Of New Two-dimensional Phosphorous And Arsenic Semiconductors And Their Physical Properties

In this paper,a new two-dimensional arsenic structure is predicted based on genetic algorithm and its physical properties are studied.we have studied the plane anisotropy of the reported P2/m-P.In addition,the properties of negative Poisson’s ratio（NPR）of the materials with hinge structure are studied.Results show as following:（1）The novel 2D single-layer arsenic structure（δ-As）belongs to the space group of Pmc2₁.The molecule is stable in thermodynamics and kinetics.Unlike the reported single-layer arsenic（gray arsenic,black arsenic,Pnm2₁-As）with indirect band gaps,the new allotrope shows direct band gap behavior.In addition,the band gap of single-layerδ-As can be adjusted from 1.83 e V to 0 e V by applying uniaxial tensile strain,which has obvious advantages for the application of solar cells and photodetectors.（2）Based on the excellent optical properties ofδ-As,a solar cell withδ-As thin film as absorbing material was designed.In the process of bendingδ-As film,the strain produced in different regions of the material is different.The film after strain treatment can be regarded as a functionally graded material（FGM）composed of single-layerδ-As with different band gap.First-principles calculations show that the FGM has good light absorption efficiency in the visible and near-infrared regions,which provides a novel design idea for solar cells with wide absorption range and high absorption efficiency.（3）The reported band gaps of single-layer arsenene and antimonene are larger than 2.00e V,which makes it possible to prepare light responsive components in the blue and ultraviolet（UV）regions.However,arsenic has unpredictable toxicity.The band gap of single-layer P2/m-P is more than 2 e V.It has high optical and electrical anisotropy.The single-layer P2/m-P has the potential to prepare blue and ultraviolet light responsive devices.（4）Single-layer BP（black phosphorus）,β-As（gray arsenic）,δ-As andγ-P（red phosphorus）have unique atomic arrangements,which belong to space groups of Pmna,Pmna,Pmc2₁ and Pbcm,respectively.Because these four structures are all hinge structures,the mechanical properties show obvious anisotropy.We report the negative Poisson’s ratio（NPR）properties of single-layerγ-P andδ-As.Their inherent NPR are-0.226 and-0.708,respectively.The value of NPR ofδ-As is about 26.2 times larger than that of single-layer BP（the NPR of single-layer BP is-0.027）.Single-layerδ-As will have great potential applications in nano sensors and electronic wearable devices.In addition,it is found that the NPR of the coupled hinge structure derives from electron effect of orbitals.