Strain Manipulation Of The Electron Transport Properties Of The Phosphoene And Its Nanostructures

In order to realize the functionalization of materials,it is necessary to control the modulation of the electronic structure and properties of materials for the real large-scale applications in the fields of quantum energy,catalysis and light,and electrical components.By constructing nanoribbons,heterojunctions,doping and adsorption,as well as applied electric fields and stresses,the mechanical,thermal,optical and electrical properties of the two-dimensional materials can be regulated.Based on the density functional theory combined with the theoretical method of non-equilibrium Green’s function,this paper investigates the excellent anisotropic mechanical properties of the phospholene in the method of the Device Studio,Nanodcal and other software.The electronic structure and transport properties of the phosphoene,phosphoene nanoribbon and P/BC₂P heterojunction are effectively controlled by means of the electric field,strain（out-of-plane strain and/or bending strain）,doping（electron and/or hole doping）and so on.Some electronic devices with novel structure,excellent performance and adjustable function are designed.The first chapter is the introduction part.Based on the spatial structure of black phosphorus and its excellent characteristics,two kinds of nano-structures of the phosphoene,the methods of manipulating the electronic properties of phosphoene are introduced.Finally,the scientific significance and main research contents of this paper are summarized.The second chapter is the theoretical basis part.Firstly,the first-principle method is briefly introduced,and the adiabatic approximation and Hartree-Fock approximation are used to solve the Schr?dinger equation for multi-particle system.Secondly,the density functional theory,the first-principles calculation method of the density functional theory combined with non-equilibrium Green’s function and the basic theory of quantum transport of mesoscopic systems are introduced.Finally,the related software packages Device Studio and Nanodcal are introduced.In chapter 3,the effects of the length of the central scattering region,the bending strain and the out-of-plane strain on the electron transport properties of the phospholene device with non-collinear electrodes are studied by using the density functional theory combined with the non-equilibrium Green’s function.The electron transmission coefficient along the armchair direction of the phospholene device has been demonstrated to be symmetrically distributed with respect to energy,while that along the zigzag direction has been found to be asymmetrically distributed with respect to energy.When the length of the central scattering region reaches 8L,the change of the scattering region length will not cause the qualitative change of the electron transmission coefficient of the phospholene device.The bending strain of 0～60°has little effect on the electron transport properties of the phospholene devices.The out-of-plane compression strain of-15%may significantly enhance the electron transmission capacity of phospholene devices along the armchair/zigzag direction,while the out-of-plane tensile strain of+15%weakens the electron transmission capacity of phospholene devices along the armchair/zigzag direction.When the external strain and bending strain act on the device simultaneously,the transport properties of the phosphoene device are mainly controlled by the external strain.In chapter 4,based on the first-principles method of density functional theory and non-equilibrium Green’s function,we investigate the electron transport properties and its strain manipulation of the armchair-edge and zigzag-edge phospholene nanoribbon devices.The obtained results show that the current of the armchair-edge phospholene nanoribbons increases linearly in the range of 0～0.40 V,oscillates in the range of0.40～0.80 V,and decreases gradually in the range of 0.80～1.00 V.The current of the zigzag-edge phospholene nanoribbon device increases linearly in the range of 0～0.30 V,oscillates in the range of the absolute bias voltage 0.30～0.60V and increases rapidly in the range of 0.60～1.00 V.Furthermoe,the effect of the bending strain on the armchair-edge and/or zigzag-edge phospholene nanoribbon has been investigated,and armchair-edge phospholene nanoribbons has been found to be more sensitive to the bending strain.The above research results are strongly verified by the conductance and the integral area of the electron transmission coefficient in the bias window.In chapter 5,the effects of finite bias and n-type electron and p-type hole doping on the electron transport properties of the armchair-edge and zigzag-edge P/BC₂P heterojunction devices are demonstrated by using the first-principles calculation method combining the density functional theory and non-equilibrium Green’s function.The current of the armchair-edge and zigzag-edge P/BC₂P heterojunction devices increases linearly at low bias voltage,and changes nonlinearly with the increase of the absolute bias voltage.Compared with the same width of the phosphoene nanoribbons,the current of the armchair-edge P/BC₂P heterojunction device increased faster than that of the armchair-edge phosphoene nanoribbon device,and the current of the zigzag-edge P/BC₂P heterojunction device increased slower than that of the zigzag-edge phosphoene nanoribbon device.The conductance of the armchair-edge P/BC₂P heterojunction device increases or decreases by 20%in the range of 0.001 e/atom～0.01 e/atom for p-type hole doping,and oscillates and decreases in the range of 0.001 e/atom～0.01e/atom for n-type electron doping.The P-type hole doping increases the conductance oscillation of the zigzag edge P/BC₂P heterojunction device,and the N-type electron doping increases the conductance of the zigzag edge P/BC₂P heterojunction device firstly,then decreases and then increases.The sixth chapter summarizes the research method,content and conclusion of this paper,and briefly expounds the innovation of this paper and its scientific significance,and gives a brief outlook for the later works.