Structural, electronic and magnetic properties of the Si chains doped zigzag AlN nanoribbons

The structural, electronic and magnetic properties of the zigzag Si chains substituting for zigzag Al-N chains in hydrogen terminated hexagonally Al-N nanoribbon with 7 zigzag Al-N chains across the ribbon width (7-ZAlNNR) have been investigated systematically using the first-principles calculations. The longer Si-Si bond length leads to a decrease (increase) in armchair (zigzag) Al-N bond length. The pure 7-ZAlNNR is a non-magnetic indirect semiconductor with a large indirect band gap of 2.979 eV. The Si chains doped 7-ZAlNNR is always metallic regardless of the Si chains doping concentrations, while the induced magnetic moment depends on the Si chains doping concentrations, increasing from 0.11 mu(B) for Si-2-7-ZAlNNR to 0.45 mu(B) for pure 7-ZSiNR. The very low Si chains doping concentration makes the Si-1-7-ZAlNNR a zero magnetic moment. Compared with the total DOS of the pure 7-ZAlNNR, the total DOS of the Si chains doped 7-ZAlNNR is not only broadened and shifted towards the low energy region but also transformed to metal. The magnetic moments of the Si chains doped 7-ZAlNNR are resulted from the zigzag Si chains but are not from zigzag Al-N chains because the Si-Si bond is a covalent sigma bond with nonbonding pi electrons while the Al-N bond is an ionic bond. Furthermore, on zigzag Si chains, the magnetic moments are mainly localized on the edge Si atoms decaying parallel (antiparallel) to the same (different) inner sub-lattices. With increasing Si chains doping concentration, both spin channels enlarge their distribution regions and thus magnetic moments. (C) 2014 Elsevier B.V. All rights reserved.