First-principles Study Of Nanobelts And Carbon-doped Aluminum Nitride, Aluminum Nitride Nanobelts / Sheet

During the last few decades, graphene nanoribbons (GNRs) have been prepared experimentally by using conventional device set up and attracted immense interest owing to their fascinating structural and electronic properties as well as promising applications in nanoelectronics. Theoretically, the GNRs with zigzag edge (ZGNR) possesses partly flat bands in the region2π/3≤|k|≤π at the Fermi level. These states were termed'edge states'because their charge densities are strongly localized at the zigzag edge sites. In addition, someone found that these edge states were not peculiar to ZGNRs, similar edge states were also presented in the energy gap of BN nanoribbons (BNNRs) with zigzag edge (ZBNNRs). Due to the polarity of the B-N bond, BNNRs may possess novel properties different from GNRs leading to new potential applications in optics and nanoscale electronic devices. Besides GNRs, both the BNNRs, A1N nanoribbons (AlNNRs) and GaN nanoribbons (GaNNRs) have also been successfully synthesized in the experiments. Among the group III nitrides, A1N is the largest band-gap semiconductor with a value of6.2eV, which is characterized by high thermo stability and conductivity and reliable dielectric properties. So AlNNRs become one of the potential nanometer materials in the wicked environment. And that in2003, the novel morphology of nanoribbons-serrated nanoribbons of pure crystalline A1N were obtained by chloride assisted vapor-solid (VS) route. In addation, preciously studies reported that the function and applications of A1NNRs can be improved after appropriate change, such as doped or substituted. Therefore, in the present paper, the structural and electronic properties of the hexagonally bonded hetero-sheets A1NCX (x=2,4,6) consisting of A1N and graphite strips with zigzag shaped borders as well as a single C chain doped zigzag A1N nanoribbon terminated with H atoms at both edges and perfect AlNNRs have been investigated systematically by using 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) In6-ZA1NNR, 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 A1and N atoms, respectively. Introducing the graphite strip Cx and increasing its width lead to the LUCB and HOVB getting closer with each other especially in flat dispersion region around the zone boundary Jy, thus decreasing in the energy gap of the hetero-sheets AINC2, AINC4and A1NC6successively. Similar to the edge states existing in zigzag edged A1NNRs, the flat dispersion border states also exist in the zigzag borders of hexagonally networked hetero-sheets A1NCX. Unlike the edge states whose charges are localized at one of the edge atoms, the border states are localized at two atoms of the borders with either bonding or antibonding character.(2) In perfect A1N nanoribbon with7zigzag Al-N chains across the ribbon width (7-ZA1NNR), the LUCB HOVB at zone boundary Z are edge states whose charges are localized at edge Al and N atoms, respectively. Introducing a single C-chain and changing its position lead to the LUCB and HOVB getting closer with each other. Similar to the edge states existing in perfect ZAINNRs, the flat dispersion border states also exist in a single C-chain decorated ZA1NNR, but their charges are localized at border C-N and C-Al for LUCB and HOVB, respectively. Furthermore, for NZ-ZA1NNR-C(n) with ribbon width Nz=2,3,4,5,6,7and10, only Nz-ZAINNR-C(1) has a direct band gap, while the other NZ-ZA1NNR-C(n) has an indirect band gap. Variation of the band gap with C-chain position n shows that, for NZ-ZA1NNR-C(n) of arbitrary width Nz, the N2-ZA1NNR-C(1) and NZ-ZA1NNR-C(2) have nearly identical the minimum band gap of0.132eV and nearly identical the maximum band gap of1.0eV, respectively, except the maximum band gap of0.63eV for2-ZA1NNR-C(2) because it belongs to the group of C-chain substituting the right edge A1-N chain, the band gap of this group decreases linearly with increasing ribbon width Nz. For3-,4-,5-,6-,7-and10-ZAINNR-C(n), the band gap decreases successively for C-chain position n from2to3,4,5,6,7and10respectively.