Defect Charged States And Oxygen Dissociation Induced By Vacancies In Phosphorene

Two-dimensional(2D)materials consist of only a few atomic layers.Compared with three-dimensional materials,the carrier migration of two-dimensional materials is limited to two-dimensional planes,exhibiting many excellent properties which is expected to solve the new generation of high-performance technical bottlenecks brought by the limit of material scale.In 2014,people prepared two-dimensional single-layer Black Phosphorus by mechanical exfoliation,named Phosphorene.Due to its unique properties,it has important application prospects in nanoelectronics and optoelectronics.Nonetheless,various defects and rapid degradation behavior in the air severe limit the application of phosphorene.As we all know,intrinsic defects and impurities are usually unavoidable in the preparation of real materials.Most point defects and impurities can occur in a variety of charge states,and can affect the physical and chemical properties of the material to a certain extent.In addition,the lone exposed on the surface of the phosphorene has a high activity on electrons,leading to the phosphorene surface rapidly oxidation under the external environment,which will affect the performance of the phosphorene electronic device.More importantly,the defects may provide high active sites,which will greatly affect the interaction of phosphorene with environmental molecules in the air.Therefore,it is very important to systematically study the defective electronic states of phosphorene,the effects of defects on oxidation reactions,and related physical mechanisms.In this paper,the first-principles calculation method is used to systematically study the typical single vacancy SV(5 | 9)and double vacancy DV(5 | 8 | 5)defect electronic states and related surface oxidation mechanisms in phosphorene.The results show that both the single vacancy SV(5 | 9)and double vacancy DV(5 | 8 | 5)-I defects can reach a stable +1 charge state.It has a great influence on the geometrical structures and electronic properties of the phosphorene defects.The defect configurations and the local bond lengths around the defects are very sensitive to the charge state.The simulation calculation of the reaction pathway by Ci-NEB,we found that vacancy defects can significantly reduce the reaction barriers for the dissociation of oxygen molecules.More importantly,we proposed a unique double oxidation mechanism on the double vacancy surface of 2D materials.Under this reaction mechanism,the oxidation reaction barrier is0.26 e V,which provides a theoretical mechanism for the rapid degradation of phosphorene in the air.Besides,the oxidation reaction can change the electronic states of vacancy defects.Finally,by analyzing the electronic structure of phosphorene after oxidation,which can further explain the decrease in P-type doping and the modest increase of the band gap observed in the phosphorene sheet exposed to the external environment in the experiment.This work is of great significance for various applications of phosphorene-based high-performance devices in defect engineering.