Investigation On Transport Properties Of Black Phosphorus Based On Continuous Approximation

In this paper,the anisotropic transport properties of black phosphorus materials under continuous approximation are studied theoretically.Our study includes the transport properties of black phosphorus after applied electric field and barrier on black phosphorus,and a new physical model of black phosphorus without applied external field.The full text is divided into the following five parts:Chapter 1 is an introduction.Firstly,the research background,motivation and some important research progress of nanomaterials and nanodevices in recent years are introduced.Particular attention has been paid to graphene and black phosphorus,which have attracted many researchers’interest in recent years.Then it introduces the theoretical methods adopted in this paper,and briefly describes how to use wave function continuity and transfer matrix to solve specific problems.In the second chapter,we mainly study the quantum transport of electrons with vertical electric field applied on monolayer and bilayer phosphorene.The transport probability of electrons through black phosphorus material is an oscillation function of incident angle,electric field intensity and incident energy of electrons.Due to the different effective mass of black phosphorus in different directions,the transport properties in two directions are different,so the critical angles of electron tunneling in different directions are different.The opening or closing of transport can be controlled by adjusting the field strength of the applied electric field.In addition,conductivity also exhibits strong anisotropic behavior in different directions,and the width of conductive gap increases with the increase of the number of layers of black phosphorus material.When given the incident energy of electrons and electric field strength,the anisotropy of transport increases with the increase of the number of layers of black phosphorus material.Therefore,in order to control the transport properties of black phosphorus materials,the application of vertical electric field is an effective method.These properties will provide a good theoretical basis for the design of microelectronic devices with better performance in the future.In the third chapter,the anisotropic transport of black-scale materials with a single barrier is studied based on the continuous approximation.The research object is expanded from monolayer phosphorene to multilayer phosphorene.Different from the regulation of the band by the applied vertical electric field,the conduction band and valence band of the black phosphorus material will be close to the Fermi level from two different directions at the same time,making the band gap smaller;the conduction band and valence band of the black phosphorus material will move upward or downward as a whole if a single potential barrier is applied,and the band gap will not change.In the study of transport properties,it is found that the critical angles of different transport directions vary with the number of layers of black phosphorus materials,whether n-n junction or n-p-n junction,after applying single barrier.The conductivity of black phosphorus material in single barrier structure also shows significant anisotropy.The difference of conductivity decreases with the change of the number of black phosphorus layers from 1 to 3.These properties indicate that it is also effective to control the transport properties of black phosphorus materials by applying a suitable single barrier.In Chapter 4,we study a physical model of black phosphorus consisting of monolayer and bilayer phosphorene.For this model,we find that the incident direction of carriers is different,and the critical angle and the peak value of transport probability will show different results.The reason for this phenomenon is that dbilayer phosphorene has smaller band gap and better transport performance than monolayer phosphorene.Finally,when we study the anisotropy of the conductivity of the system,we can see that for the same incident energy and transport direction,the higher conductivity is emitted from the black phosphorus side of the monolayer phosphorene.This model does not need to apply external field,and only needs to adjust the incident energy to adjust the transport performance of the system.The last part is a brief summary of this paper.