Investigation On The Magnetic And Electronic Properties Of H-BN And Phosphorene Systems

In recent years,the successful fabrication of graphene made the viewpoint that two-dimensional materials cannot exist stably denied,and also because of its unique physical properties,low-dimensional materials have been widely studied.For example,the monolayer hexagonal boron nitride and phosphorene is synthesized successfully.Investigations show that both of them have superior electronic properties,and these properties are easy to be manipulated by introducing defects,atoms terminated in the edge,surface adsorption,strain,and applied electric field.In other words,various magnetic structures,such as ferromagnetic metals,half-metals,spin gapless semiconductors,half-semiconductors,and bipolar magnetic semiconductor,can be obtained by functionalizations.Therefore,low-dimensional materials have great potential for applications in spintronic devices.In this work,we systematically studied the geometry as well as magnetic and electronic properties of novel nano-structures based on the monolayer hexagonal boron nitride and phosphene by using first-principles method based on the density functional theory(DFT).And also,we investigate how to control its magnetic and electronic properties by strain and applied electric field.Our investigation will provide viable references for the research and design of spintronic devices.Firstly,We make an introduction of the research progress of hexagonal boron nitride and phosphorene materials and the theoretical methods we use.Followed this,we investigate the 558-type line defect introduced zigzag BN nanoribbons and find that such a structure is highly stable.In the nonmagnetic state,the metallic property of ZBNNRs remains unchanged regardless of the defect positions,but different defect positions give rise to different influences on the total DOS and PDOS at the Fermi level.While in the magnetic state,the thermal stability of magnetism is enhanced greatly when the line defect appears at most positions,even comparable with room temperature.When the line defect position shifts from the B-edge to the N-edge,the transition from the half-metal to the magnetic semiconductor or spin unpolarized semiconductor is induced.And also,the response of defect ribbons to an in-plane transverse electric field is essentially different from defect-free ribbons,and the half-metallic feature can be enhanced by an electric field for the line defect introduced into certain positions in a ribbon.Then,we study the tunable magnetic and electronic properties of O terminated ZBNNRs under axial strain and electric field.The O dimerization formed in the B edge makes it more stable than hydrogen terminated ZBNNR,and it can bear the deformation of more than 22%.Also,it has good thermal stability even if strain is generated.Its nature mainly depends on the O atom in the N edge,and the strain is also influence the N edge.Uniaxial deformation can tun it from magnetic metal(FM state)to non-magnetic metal,spin gapless semiconductor(FM state)and non-magnetic semiconductor(AFM state).It will be half-metallic under a suitable applied electric field.For its asymmetric structure,the intrinsic electric field appearing in the nanoribbon can be changed by the strain and an applied electric field.We also study the carrier mobility of transition metal atom doped armchair phosphene nanotubes.It is found that Ti,Mn,Fe and Ni atom-substituted APNTs are all magnetic semiconductors,in which the cases of Ti,Mn and Fe doping are half-semiconductors,but Ni doping leads to a bipolar magnetic semiconductor.All of them have extremely high thermal stability and energetic stability,although Mn doped APNTs has slightly lower energetic stability.All doped nanotubes can achieve high carrier mobility,even more than 103 cm2V-1s-1 at room temperature.When an electric field is applied to Ni doped nanotube,the effective mass and deformation potential will change,which will greatly increase its the carrier mobility.Even when a 3V/nm electric field is applied,the carrier mobility reaches 104 cm2V-1s-1 or more.Finally,we investigated the transition metal atoms embedded in the monolayer hexagonal boron nitride and phosphene heterostructure.Results show that V-embedded heterostructure is a semi-semiconductor,Mn embedded heterostructure is a magnetic metal,and Fe embedded heterostructure is a bipolar magnetic semiconductor.In addition,both V and Mn embedded heterostructures have a large magnetic moment.Although Fe has a small magnetic moment,it can adjust the magnetic moment to 2 ?B by the electric field.For the Sc embedded heterojunction,it will be a magnetic metal and eventually a half metal by a suitable applied electric field.