Si晶体中螺位错滑移特性的分子动力学

在保持Si晶体模型完全周期性的边界条件下, 采用位错偶极子模型在其内部建立一对螺位错. 通过Parrinello-Rahman方法对模型施加剪应力, 并应用分子动力学计算位错运动速度及交滑移的发生与外加剪应力间的关系. 在此基础上进一步研究晶体内的空位缺陷对螺位错运动的影响. 结果表明, 在位错滑移面上的六边形环状空位聚集体可加速螺位错的运动, 并且螺位错能通过交滑移跨越该空位缺陷, 避免产生钉扎现象. 揭示了低温层中大量存在的空位缺陷是降低位错密度的原因. 

Molecular Dynamics of Screw Dislocation Motion Characteristic in Si Crystal

To get the screw dislocation motion characteristic in the growing process of lattice mismatched heterostructures,a pair of screw dislocations is introduced in a full periodic Si crystal via dislocation dipole modeling.The screw dislocation motion velocity and cross-slip versus the shear stress applied by Parrinello-Rahman method are investigated by utilizing molecular dynamics simulation technique.In addition,how the motion of screw dislocation is affected by a vacancy defect is investigated.It is found that a ring-shaped hexagonal vacancy located in the dislocation slip plane can facilitate the motion of the screw dislocation.The motion velocity is increased in comparison with that of the model without vacancy defect.The screw dislocation can eventually stride over the ring-shaped hexagonal vacancy during cross-slip,preventing from being pinned.These results reveal the basic mechanism of LT-Si technology,i.e.,a large amount of vacancy defects located in Si layer can eventually reduce the dislocation density due to the dislocation motion characteristics.