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

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The structural, electronic and magnetic properties of the zigzag Si chains substituting for zigzag Al–N chains in hydrogen terminated hexagonally AlN 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 2.979eV. 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 0.11μB for Si2–7-ZAlNNR to 0.45μB for pure 7-ZSiNR. The very low Si chains doping concentration makes the Si1–7-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 σ bond with nonbonding π 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.