Tunable Magnetic And Transport Properties In IVA-VA Low Dimensinal Nanostructures

The so-called”d⁰magnetism”is a new approach to induce magnetism in materials,in which the systems do not contain any ions with partially filled d or f orbitals.This type of”d⁰magnetism”provides a new effective way to modify series of materials to own high-temperature magnetism for the need of spintronics.Especially,the low dimensional systems,with the quantum confined effects,large surface effect and strong interface interaction,always exhibit exotic quantum properties and are ideal systems to maintain and enhance d⁰magnetism.In this thesis,based on first-principles density functional theory?DFT?calculations,we have investigate the d⁰magnetism in arsenene,IVA-VA nanoribbons and layered graphene,as well as their spintronics device transition properties.The main results are as follows:?1?Performing a first-principles density functional theory calculation,we have in-vestigated the electronic and d⁰magnetic properties in doped arsenene and its spintronic device transition properties.We found that the strong localized poten-tial of the lone pairs of arsenene can yield strong coulomb force to its dopping states and exhibit d⁰magnetism in enven number of valence electrons dopants.Further,we investigate the effect of strain on its d⁰magnetism.we found that the strain performance different effect which is decided by the spin polarized dopping states.For C,Si,Ge,the strong localized P_zorbital on the dopnats formed the mag-netism,and their magnetism decrease monotonously as the strain increase.For Be,Mg,Ca and O,S,Se,their magnetism are induced by the dopants neighboring As P_xand P_yorbital and their magnetism incerase firstly as the strains reached a certain strength,and then decrease as the strains go on growing.Finally,we have investigate the C doped arsenene spintronics device and found it can produce strain tunable spin polarized current.what's more,we have expand the system to graphene quantum dots in arsenene to develop the device performance.?2?Performing a first-principles density functional theory calculation,we have in-vestigated the electronic and magnetic properties of the ZIV-VNRs.We found that a various charge and magnetic states can be formed in ZIV-VNRs,due to the competition between charge,spin and lattice degrees of freedom in different localization natures of the edge states.In their edges,FM semiconducting ground states are found for ZCPNRs and ZCAs NRs,while AFM states are preferred for ZSi PNRs and ZSi As NRs.Further,We find a Peierls-like distortion semiconduct-ing state could also take place in ZSi PNRs and ZSi As NRs,for the bonding of their edge state is weaker and the spin ordering are broken by electron-lattice coupling through energy barrier.?3?Performing a first-principles DFT calculation,we have propsed two new kinds of 2D materials of silicon and arsenic compound Si As and Si As₂,which are both dynamically and thermodynamically stable.Our caculations show that Si As and Si As₂monolayers are indirect semiconductors with the band gaps of 2.39e V and2.07e V,respectively.The band gap of Si As and Si As₂monolayers are sensitive to strain,which undergo an indirect to direct band transition and even to metal upon certain mechanical strain.Si As and Si As₂monolayers possess higher mobility than Mo S₂and display anisotropic transportation like the black phosphorene.?4?we have preliminary investigate the spin valve effect on d⁰magnetism multilayer grpahene inducing by hydrogen adsorption.