单晶锗裂纹扩展行为的仿真与实验研究

单晶锗加工时裂纹的产生严重影响表面质量,为进一步探究单晶锗裂纹扩展的影响因素,通过分子动力学仿真方法,对不同晶面的表面能进行了计算,模拟了不同晶面、同一晶面不同取向以及不同温度对单晶锗裂纹扩展行为的影响,并通过纳米压痕实验对仿真结果的准确性进行了验证。结果表明:单晶锗(110)晶面的表面能最小且更易产裂纹。裂纹在同一晶面不同取向上的扩展行为呈现出周期性镜像对称现象,裂纹尖端出现应力集中和原子错配现象,使得裂纹扩展呈现子母裂纹且路径偏移。在其他条件不变的情况下,适当降低温度更有利于提高裂纹临界扩展应力,降低扩展速率,从而达到抑制裂纹扩展,提高单晶锗加工表面质量的效果。通过纳米压痕实验,发现不同取向下,裂纹扩展的难易程度不同,随着压载的增大,分别出现了45°最长裂纹,165°最易产生裂纹,285°最难产生裂纹并且裂纹最短。

Simulation and experimental study on crack propagation behavior of single crystal Germanium

Single crystal germanium cracks will seriously affect the surface quality when machining, In order to further explore the influencing factors of single crystal germanium crack growth, this paper uses molecular dynamics simulation methods to calculate the surface energy of different crystal faces,the effects of different crystal planes,different orientations of the same crystal plane, and different temperatures on the crack propagation behavior of single crystal germanium are simulated,and the accuracy of the simulation results is verified by nanoindentation experiments.The results show that the surface energy of (110) crystal plane of single crystal germanium is the smallest and cracks are more likely to occur.The propagation behavior of cracks on the same crystal plane with different orientations presents periodic mirror symmetry. Stress concentration and atomic mismatch phenomenon appear at the crack tip, which makes the crack propagation present a mother-child crack and a path deviation. When other conditions remain unchanged, appropriately lowering the temperature is more conducive to increasing the critical crack propagation stress and reducing the expansion speed, so as to achieve the effect of suppressing crack propagation and improving the surface quality of single crystal germanium processing.Through the nanoindentation experiment, it is found that the difficulty of crack propagation is different under different orientations. With the increase of ballast, the longest crack appears at 45°, cracks are most likely to occur at 165°, and the most difficult to occur at 285° Cracks and the shortest cracks.