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为了研究晶格常数不匹配的异质结结构(Si1-xGex/Si)在生长过程中低温缓冲层内的位错运动特性,在Si晶体中建立了60°位错偶极子,以及相对于位错不同空间位置的5种六边形环状空位缺陷模型.基于分子动力学理论,并通过Parrinello-Rahman方法施加剪应力使位错运动,研究了不同空间位置空位缺陷对于60°位错运动的影响,发现各种类型的空位缺陷均会阻碍位错运动,导致位错线弯曲,而位错远离空位缺陷的部分在交会过程中出现了先加速、后减速的现象.模拟结果表明:使位错不被钉扎住的临界外加剪应力随着温度的上升而减小,在上述模型中当温度达到300K以上就稳定于0.6 GPa附近,小于SiGe体系中的失配应力,说明空位缺陷不会成为60°位错的钉扎点,仅会对其运动产生迟滞.
In order to study the dislocation motion in the low temperature buffer layer of the heterojunction structure (Si1-xGex / Si) with mismatched lattice constant, a 60 ° dislocation dipole was established in the Si crystal, Five kinds of hexagonal annular vacancy defect models in different spatial positions of dislocation.Based on the molecular dynamics theory, shear stress was applied by the Parrinello-Rahman method to make dislocation motion, and the effects of different spatial positions of vacancy defects on dislocation movement of 60 ° , It is found that all kinds of vacancy defects will impede the movement of dislocations and lead to the bending of dislocation lines and the part of the dislocations far away from the vacancy defects appear to accelerate and then decelerate in the process of rendezvous.The simulation results show that The critical applied shear stress of dislocations not pinned decreases with the increase of temperature. In the above model, when the temperature reaches above 300K, it stabilizes at around 0.6 GPa and is less than the misfit stress in SiGe system, indicating that vacancy defects are not Will become a pinpointing point of 60 ° dislocation, will only hysteresis of its movement.