Abstract Structural, electronic and magnetic properties of the nickel doped AlN (0 0 0 1)-(2 × 2) surfaces are investigated by spin-polarized first-principle total-energy calculations. The exchange–correlation potential energies are treated within the generalized gradient approximation (GGA) with the Perdew, Burke and Enzernof (PBE) functional. Electron-ion interactions are dealt with the pseudopotential approach. According to results the H3 site is the most favorable structure in the adsorption of Ni at different coverage from ¼ to 1 monolayer (ML). When coverage is in the range from ½ to 1 ML, we found ferromagnetic (FM) behavior as a consequence of the Ni presence with magnetic moment (>0.7 μB/atom). Also, we found the formation of dimers, trimers and atomic chains in the ½, ¾ and 1ML coverage, respectively. The minimum energy pathways in the Ni adsorption and incorporation show activation energies of 1.53 and 1.26 eV, respectively. The deposit of Ni into substitutional sites suggests the possibility of growing NiN epitaxially. We employed the surface formation energy formalism to investigate the different structures stability. Results indicate that the Ni doping is favorable under Ni-rich conditions in all the range of chemical potential Δ μ AlN , finding four AlN surfaces with different magnetic properties: the 1Ni ads and 4Ni subs models are non-magnetic, however the 1Ni subs model is FM and the 2Ni subs model is antiferromagnetic (AFM) with magnetic moments of the order of 0.8 μB/atom. Therefore, we can conclude that high concentrations of Ni induce a non-magnetic behavior, and low concentrations favor the magnetic properties, provided that the Ni atoms occupy substitutional sites. The density of states shows that only the 1st ML of surfaces is metallic, in contrast layers beneath the first layer are semiconductor, where the valence and conductions bands are mainly formed by the N-p and Al-p orbitals, respectively.

中文翻译：

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掺杂镍的 AlN (0001)-(2×2) 表面的理论研究：结构、电子和磁性

摘要 通过自旋极化第一性原理总能量计算研究了掺杂镍的 AlN (0 0 0 1)-(2 × 2) 表面的结构、电子和磁性能。交换相关势能在广义梯度近似 (GGA) 内使用 Perdew、Burke 和 Enzernof (PBE) 函数进行处理。电子-离子相互作用采用赝势方法处理。根据结果​​，H3 位点是在从 1/4 到 1 单层 (ML) 的不同覆盖率下吸附 Ni 中最有利的结构。当覆盖范围在 ½ 到 1 ML 范围内时，我们发现铁磁 (FM) 行为是由于 Ni 存在磁矩 (>0.7 μB/原子) 的结果。此外，我们分别在 ½、¾ 和 1ML 覆盖范围内发现了二聚体、三聚体和原子链的形成。Ni 吸附和掺入的最小能量途径分别显示 1.53 和 1.26 eV 的活化能。Ni 沉积到替代位点表明 NiN 外延生长的可能性。我们采用表面形成能形式来研究不同结构的稳定性。结果表明，在所有化学势 Δ μ AlN 范围内，在富 Ni 条件下，Ni 掺杂是有利的，发现四个具有不同磁性的 AlN 表面：1Ni ads 和 4Ni subs 模型是非磁性的，而 1Ni subs 模型是 FM，2Ni subs 模型是反铁磁 (AFM)，磁矩为 0.8 μB/原子数量级。因此，我们可以得出结论，高浓度的 Ni 会导致非磁性行为，而低浓度的 Ni 有利于磁性，条件是 Ni 原子占据置换位点。态密度表明只有第 1 个表面是金属的，而第一层之下的层是半导体，其中价带和导带主要分别由 Np 和 Al-p 轨道形成。