Theoretical Study On Geometry Structure And Electrical Properties Of Phosphorus And Aluminum Doped Boron Nitride Nanotubes

Boron nitride nanotubes are one kind of semiconductor materials which have simple and stable electrical properties. They have large band gaps, which are unconcerned with their structural parameters, such as their diameter, helicity, chirality and the number of the plies of the tube's wall and so on. Boron nitride nanotubes' poor electrical conductivity makes them like insulators. Based on their inherent limitations, we can change their geometry structure and electrical properties by doping other atoms to obtain the required materials.In order to investigate the influence of different concentration and situation to the phosphorus and aluminum doped single-wall boron nitride nanotubes, the first principle of the density functional theory was used to calculate the geometry structure, the formation energy of the doped systems, the structure of electron energy band and the density of states of one period and three periods P, Al-doped single-wall armchair boron nitride nanotubes. Here, we use the software of Material Studio to construct the molecular model and apply the module of Castep to calculate their geometry structure and electrical properties.The results showed that the geometry structures of all the doping systems changed and the symmetry reduced. The formation energy of impurity increased along with the increase of the concentration of impurity. And the formation energy of P-doped systems was much larger than the corresponding of Al-doped systems. Furthermore, the formation energy of different situation of two atoms doped together was little distinction whereas much larger than any single atom doped systems'. The energy band gap of the P atoms and Al atoms doped into three periods'boron nitride nanotubes decreased with the increase of the concentration of the doping atoms. But to the different situation of the doping atoms, the energy band gaps were almost the same. Moreover, to the one period boron nitride nanotubes, we could further conclude that the concentration and situation of the different impurity atoms caused different impurity energy band and the number of energy band between the top of valence band and the bottom of conduction band was 2n (n is the number of impurity atoms). Furthermore, the attributions of all systems'electronic density of states were almost from the electrons of p orbits. The attributions of s orbits are less. And to the doping systems, the attributions of the electronic density of states are from the doping atoms'electrons of p orbits. The results show that boron nitride nanotubes doped with phosphorus atoms and aluminum atoms replacing N atoms and B atoms, which cause great changes in electrical properties, and the system has the characteristics of a conductor or a semiconductor.