The Induced Magnetism Of 2D Nonmagnetic Heterojunctions Via Non-compensated Bonding

Compared with bulk materials,two-dimensional nanomaterials have many excellent properties.Packing two-dimensional materials together in different ways can form two-dimensional van der Waals heterojunctions,which have attractive properties.Experimental and theoretical studies have found that the electronic and magnetic properties of two-dimensional van der Waals heterojunctions can be regulated by different kinds of methods.This thesis mainly studies the effect of non-compensated bonding on the electronic and magnetic properties of nonmagnetic BN/Graphene,Zn O/Ga N heterojunctions.The main contents are as follows:(1)Magnetized graphene is a promising candidate for spintronic devices,where half-semimetallic or-semiconducting property is highly desirable.Using first-principles calculations and further analysis,we show that stable ferromagnetic ordering can exist readily in non-compensated bonding BN/Graphene bilayer with triangular defects by analogizing with compensated bonding BN/BN bilayer observed in experiment.More intriguingly,regardless of the non-compensated defect states in the gap,such spin-polarized BN/graphene bilayer exhibits spin-gapless and-gapped semiconducting band structures with quadratic and linear dispersion,respectively,depending on the size of triangular defects.The massive or massless electronic states of bonding BN/Graphene are associated with the electron localization degree at the zigzag edges of triangular defects.Our findings might provide another feasible strategy to realize stable magnetized graphene and engineer its electronic and magnetic features.(2)Based on the already findings that non-compensated bonding could significantly affect and tune the electronic and magnetic properties.We next study whether such the non-compensated bonding and underlying mechanism still work in other nonmagnetic heterojunctions such as Zn O/Ga N bilayer.We find nonmagnetic Zn O/Ga N heterojunction takes on direct semiconducting properties.Further investigations show that the formation energy of triangular defects depends linearly on the size of the defects,which is well in line with that of non-compensated bonding BN/Graphene bilayer.However,the non-compensated Zn-N bonding induced magnetic behavior is dramatically different from the case of C-N non-compensated bonding BN/Graphene,which can not be explained wholly by Lieb's theory.In the former case,the induced magnetic moment also depends linearly on the size of defects,while for the latter case the one shows oscillating behavior.Such dramatically different characteristic of non-compensated bonding induced magnetic moment in different nonmagnetic heterojunctions could provide an effective method to delicately tuning their electronic and magnetic properties.