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采用基于密度泛函理论的第一性原理平面波超软赝势方法,计算了纤锌矿型AlN中引入不同电荷态的N空位和Al空位时结构中最大局域化Wannier函数,并根据Wannier函数的空间分布及空间分布的几何中心位置,对空位引起的晶体电子结构变化及[0001],[ˉ1010],[ˉ12ˉ10]晶向上的自发极化进行了研究.结果表明,利用最大局域化Wannier函数分析电子结构具有直观的特点,清晰地表明N—Al键具有较强的离子性.研究发现,N空位结构中悬挂键上电荷向空位处转移,而Al空位结构中悬挂键上电荷则远离空位,沿悬挂键方向移动到N原子一侧.同时发现,空位的引入破坏了[ˉ1010],[ˉ12ˉ10]晶向上的中心对称结构,产生了极化,且极化强度随着空位电荷态的增加而增大.在[0001]晶向上,随着N空位电荷态的增加,空位周围电子结构发生了剧烈变化,使得自发极化发生了逆转,极化强度随着电荷态的增加而增大;而在Al空位中,随着电荷态的增加,自发极化沿原方向显著增加,但没有发生极化反转.
Based on the first principle plane wave super soft pseudopotential method based on density functional theory, the maximum localized Wannier function in wurtzite AlN with different charge states and Al vacancies is calculated. According to the Wannier function And the geometrical center position of the spatial distribution, the vacancy-induced changes of the crystal electronic structure and the spontaneous polarization in the [0001], [ˉ1010], [ˉ12ˉ10] crystal directions were studied. The results show that the maximum localized Wannier The functional analysis of the electronic structure is intuitive and clearly shows that the N-Al bond has strong ionicity. It was found that the charge on the dangling bonds in the N-vacancy structure shifts to the vacancy and the charge on the dangling bonds in the Al vacancy structure is far Vacancy along the dangling direction to the side of the N atom.It is also found that the introduction of vacancies undermines the center symmetry structure of [ˉ1010] and [ˉ12ˉ10] crystals and produces polarization, and the polarization intensity changes with the charge state of vacancy Increases and increases.In the [0001] crystal orientation, with the increase of N-vacancy states, the electronic structure around the vacancy changes drastically, so that the spontaneous polarization reverses and the polarization intensity increases with the charge state ; In Al vacancies with increasing charge state, a significant increase in the spontaneous polarization direction of the original, but the polarization inversion does not occur.