| With the advancement of the science and technology and the rapid development of the microelectronics industry,The demanding of electronic devices is more and more.The original silicon material has been unable to meet the various aspects of requirements that the smaller electronic devices,faster computing and the higher integration degree of electronic devices.For nearly two decades,scientists in physics,materials,and chemistry are looking for new materials as alternatives to silicon.We have found that graphene in the field of electromagnetics,optics,mechanics,thermal and other fields can show excellent properties,so it has been once considered a new material instead of silicon.However,the bandgap of graphene is essentially zero,so that it can not be used to fabricate high performance,and low power electronic transistors.Next,more of the two-dimensional material has been found.Such as boron nitride,molybdenum disulfide and a series of transition metal chalcogen compounds,as well as the past three years experimentally prepared black phosphorus and so on.In this paper,the electron band structure and electron transport properties of black phosphorus and molybdenum disulfide were studied.We investigate quantum transport of carriers through a strained region on monolayer phosphorene theoretically.The electron tunneling is forbidden when the incident angle exceeds a critical value.The critical angles for electrons tunneling through a strain region for different strengths and directions of the strains are different.Owing to the anisotropic effective masses,the conductance shows a strong anisotropic behavior.By tuning the Fermi energy and strain,the channels can be transited from opaque to transparent,which provides us with an efficient way to control the transport of monolayer phosphorene-based microstructures.Then we investigate the structural and magneto-electronic properties and electric field-mediated effects for zigzag phosphorene nanoribbons(ZPNRs)by different edge functionalization are investigated systematically.Here we predict half-metallicity in nanoscale phosphorene ribbons by using first-principles calculations.We show that this phenomenon is realizable if in-plane homogeneous electric fields are applied across the ZPNRs with edge functionalization and edge oxidation,and that their magnetic properties can be controlled by the external electric fields and the proportion of edge functionalization to edge oxidation.The results are not only of scientific interest in the interplay between electric fields and electronic spin degree of freedom in solids but may also open a new path to explore spintronics at the nanoscale,based on phosphorene.In the end,we investigate theoretically quantum transport through a single barrier on monolayer MoS2.It is found that the transmission properties of spin-up(down)electrons in the K valley are the same as spin-down(up)electrons in the K valley due to the time-reversal symmetry.Generally,the transmission probability for transport through an n-n-n(or p-p-p)junction is an oscillating function of incident angle,barrier height,as well as the incident energy of electrons.The present transmission shows a directional-dependent tunneling depending sensitively on the spin orientation for transport through a p-p-p junction.While for transport through an n-p-n junction,monolayers of MoS2 become opaque for almost all angles of incident ?0 except for ?0-?0(the resonant angles).The positions and numbers of resonant peaks in the transmission are determined by the distance between the two barriers and the spin orientation.The conductance in such systems can be tuned significantly by changing the height of the electric potential.In general,we systematically studied the electronic band structure of black phosphorus and molybdenum disulfide materials and the related electromagnetic properties of nanoribbons,and provided the theoretical basis for the design of electronic devices based on two-dimensional materials. |
PDF Full Text Request