Structural Line Defects In Phosphorene: A Computational Study

Black phosphorene is a two-dimensional material with hexagonal buckled structure successfully exfoliated from bulk black phosphorus.Notably,the monolayer phosphorene possesses a desirable direct bandgap of 0.91 eV and significant transport anisotropy within the monolayer plane as well as the fexible,rendering it a potential candidate for future nanoelectronic applications.Like other two-dimensional materials,defects are inevitably present in phosphorene and always can affect it's properties.However,different from other two-dimensional materials,there are many stable allotropes of phosphoenene,and the presence of these allotropes will lead to more different types of defects of black phosphorene.On the one hand,the properties and applications of phosphorene are always affected by the presence of defects.On the other hand,for phosphorene,defects also can be widely used to generate innovative devices.Based on ab initio density functional calculations,we examine five types of line-defect structures in phosphorene monolayer and present the electronic band structure and defect formation energy of various line-defect systems.We found that the defect formation energy in phosphorene is less than that in graphene.By calculating the electronic properties of the line-defect systems,the results show that defective structure still behave as semiconductors.Furthermore,the results show that the band gap of the line-defect system is related to the intrinsic band gap of the inserted structure which playing as a line defect.Among the five structural phases inserted,the smallest band gap is ?-P with a band gap of0.45 eV,which corresponds to the ?-P line defect system with the smallest band gap of 0.54 eV in the five types of line defect systems.Different two-dimensional materials are stacked to form heterogeneous structures,which have been identified as a way to improve or enrich the properties of these two-dimensional materials.In this paper,the layered structures of ?-P(blue phosphorene),?-P and ?-P(black phosphorene)are formed into four heterostructures by vertical stacking or lateral connection.We study the structure and electronic properties of these four heterostructures.For the vertical stacking heterojunction ?-P/?-P and ?-P/?-P,the calculated band gaps are 0.37 eV and 0.73 eV,respectively.The ?-P/?-P and ?-P/?-P lateral heterostructures are designed,then investigate the thermodynamic stability and electronic properties of lateral heterojunction with differentwidths.The results show that the formation energy is very small in all scales,which ensures the thermodynamic stability of the heterojunction.By calculating the electronic properties of the lateral heterojunction,we discover that the structures with different widths are all semiconductors,and the band gap of the lateral heterojunction decreases with the increase of the width.