Low Dimensional Aluminum Nitride Nanobelts And The Primary Principle Of Research

Recently, Ⅲ-Ⅴ semiconductor materials of large band gap and their device applications have attracted both scientific and technological a high tide. Group Ⅲ nitrides (BN, GaN, AlN, InN) have excellent optical properties, high temperature resistance, novel mechanical properties and less susceptible to corrosion properties. These devices in large scale integrated circuit, panchromatic high-resolution image display, color laser printing, optical storage, medical equipment, underwater and outer space communication, UV detection and other industrial and agricultural production and science and technology national defense fields have a very attractive prospect and important significance. Aluminum nitride (AlN) as one of the group Ⅲ nitrides materials, is the most wide band gap semiconductor (band gap of6.2eV), with high hardness, high thermal stability and good dielectric properties. Theoretical study shows, all AlN nanoribbons (AlNNRs) are semiconductors which are independent of the edge shape. The electronic properties of AlNNRs under the effect of extra electric field, vacancy defect are modified. This paper is aim to study the dangling bonds bring the effect of electronic structure and magnetic properties for both ZAlNNR and AAlNNR. The structural and electronic properties of the hexagonally bonded heterosheets AlNSix (x=2,4,6) consisting of hexagonal networks of AlN (h-AlN) strips and silicene sheets with zigzag shaped borders. The geometry structure and electronic properties of the zigzag edge AlN nanoribbons (ZAlNNRs) doped with a single Si chain. Use the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework under the generalized gradient approximation (GGA). The following results are obtained:1. Though AlN nanoribbon (AlNNR) with H atom termination is a nonmagnetic semiconductor, the dangling bonds cause magnetic semimetal for zigzag edged AlNNR (ZAlNNR) with bare N edge, magnetic metal for ZAlNNR with bare Al edge or bare N and Al edges, magnetic semiconductor for armchair edged AlNNR (AAlNNR) with bare N edge or bare Al edge. Due to the strong coupling of the dangling bonds of dimeric N and Al atoms at the same edge, the AAlNNR with bare N and Al edges is still a nonmagnetic semiconductor. The magnetic moment of ZAlNNR with either bare N edge or bare Al edge is nearly half of the magnetic moment of AAINNR with either bare N edge or bare Al edge due to its half number of the dangling bonds in per unit cell with respect to AAINNR cases. The larger difference charge density between the majority spin and minority spin for edge bare N atoms and decaying for N sub-lattices away from edge, as well as the smaller difference charge density for edge bare Al atoms and without decaying for Al sub-lattices away from edge indicate the magnetic moment of both ZAINNR and AAlNNR with bare N edge is larger than that of them with bare Al edge. The dangling bonds induce both ZAINNR and AAINNR with bare N edge a completely (100%) spin-polarization at the Fermi level, indicating such structures can be utilized to construct efficient spin-polarized transport devices.2. The structural and electronic properties of AlN and Si sheets, hydrogen terminated AlN and Si nanoribbons with hexagonal morphology and2,4,6zigzag chains across the ribbon width and the hexagonally bonded heterosheets AlNSix (x=2,4,6) consisting of hexagonal networks of AlN (h-AIN) strips and silicene sheets with zigzag shaped borders have been investigated using the first-principles projector-augmented wave (PAW) formalism within the density function theory (DFT) framework. The AlN sheet is an indirect semiconductor with a band gap of2.56eV while the Si sheet has a metallic character since the LUCB and HOVB meet at one k point of two thirds away from Г to Z. The results show that in semiconductor6-ZAlNNR, for example, the states of the lowest unoccupied conduction band (LUCB) and the highest occupied valence band (HOVB) at zone boundary Z are edge states whose charges are localized at edge Al and N atoms, respectively. In metallic6-ZSiNR, a flat edge state is formed at the Fermi level EF near zone boundary Z because its charges are localized at edge Si atoms. The hybridizations between the edge states of h-AIN strips and silicene sheets result in appearance of border states in the zigzag borders of heterosheets AlNSix whose charges are localized at two atoms of the borders with either bonding or antibonding π character.3. The first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework have been used to determine the geometry structure and electronic properties of the zigzag edge AlN nanoribbons (ZAINNRs) doped with a single Si chain The Si-Al, Si-N, Si-H and Al-H bonds show an ionic binding character, while the N-H bond is a typical covalent bond. These may be because of the tighter bounded N electrons with smaller orbital radius than Si and Al electrons. A single Si chain doped ZAlNNR is metallic regardless of the position of the Si chain in the nanoribbon, which comes from the Si and Al atoms especially their p orbital electrons. The ZAINNR-Sil has the smallest energy gap of between the highest valence band and lowest conduction band at Z point. The highest valence band and lowest conduction band all come mainly from the Si chain and slightly from its the nearest neighbor N atom.