基于分子动力学的纤锌矿AlN位移阈能与初级碰撞损伤模拟研究

Molecular Dynamics Study of Threshold Displacement Energies and Primary Collision Cascade Damage in Wurtzite AlN

摘要: 位移阈能是表征材料初始辐照损伤能力的重要参数。本文采用分子动力学方法研究了纤锌矿AlN中Al和N原子的方向相关位移阈能及初级碰撞级联损伤行为。位移阈能计算在10 × 10 × 6超胞中进行，选取[0001]、[$10\overline{1}0$ ]和[$11\overline{2}0$ ]四个典型晶向；单级联碰撞模拟采用20 × 20 × 12超胞，考察Al-PKA和N-PKA沿[0001]和[$11\overline{2}0$ ]晶向、在100、500和1000 eV条件下的损伤演化。通过初末态构型比较和晶格位点匹配方法，对空位、间隙及反位缺陷进行了识别与统计。结果表明：Al和N原子的位移阈能均具有明显各向异性，其中Al原子沿[0001]、[$10\overline{1}0$ ]、[$10\overline{1}1$ ]和[$11\overline{2}0$ ]晶向的位移阈能分别为44、14、10和9 eV，N原子分别为30、9、7和9 eV，表明N子晶格更易发生稳定离位；残余缺陷总数随PKA能量升高显著增加，并伴随反位缺陷形成；与[0001]晶向相比，[$11\overline{2}0$ ]晶向表现出更强的损伤空间展宽和更高的残余缺陷保留倾向。本文结果可为AlN辐照损伤模型参数选取及抗辐照器件设计提供原子尺度依据。

Abstract: Threshold displacement energy is a key parameter for characterizing the onset of radiation damage in materials. In this work, molecular dynamics simulations were performed to investigate the direction-dependent threshold displacement energies of Al and N atoms and the primary collision cascade damage behavior in wurtzite AlN. The threshold displacement energy calculations were carried out in a 10 × 10 × 6 supercell along four representative crystallographic directions, namely, [0001], [$10\overline{1}0$ ], [$10\overline{1}1$ ], and [$11\overline{2}0$ ]. Single-cascade simulations were performed in a 20 × 20 × 12 supercell to examine damage evolution induced by Al-PKAs and N-PKAs along the [0001] and [$11\overline{2}0$ ] crystallographic directions at 100, 500, and 1000 eV. Vacancies, interstitials, and antisite defects were identified and quantified by comparing the initial and final atomic configurations using a lattice-site matching method. The results show that the threshold displacement energies of both Al and N atoms exhibit pronounced anisotropy. For Al atoms, the threshold displacement energies along [0001], [$10\overline{1}0$ ], [$10\overline{1}1$ ], and [$11\overline{2}0$ ] are 44, 14, 10, and 9 eV, respectively, whereas those for N atoms are 30, 9, 7, and 9 eV, indicating that the N sublattice is more susceptible to stable atomic displacement. The number of residual defects increases significantly with increasing PKA energy and is accompanied by the formation of antisite defects. Compared with the [0001] crystallographic direction, the [$11\overline{2}0$ ] crystallographic direction shows stronger spatial spreading of cascade damage and a higher tendency for residual defect retention. These results provide atomistic support for the parameterization of radiation-damage models and the design of radiation-tolerant AlN-based devices.