Investigate the mechanical property of nanopolycrystal silicon by means of the nanoindentation method
Investigate the mechanical property of nanopolycrystal silicon by means of the nanoindentation method
复制标题
利用纳米压痕法研究纳米多晶硅的力学性能
DOI：
10.1063/5.0002785
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发表时间：
2020
期刊：
影响因子：
1.6
通讯作者：
Xuesong Han
中科院分区：
文献类型：
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作者：
Xuesong Han
全面了解基本的变形机制是必不可少的新的纳米材料具有独特的性质，工程应用。然而，由于纳米多晶材料的晶粒尺寸较小，制备难度较大，这就给变形过程的实验研究带来了困难。分子动力学（MD）方法已经被证明是研究纳米尺度现象的有效工具，并逐渐被许多研究者用于研究纳米材料的机械变形。本文利用分子动力学模拟方法研究了内部晶粒被大角度晶界分隔而无孔隙和杂质的试样的力学响应。结果表明，如果晶粒尺寸足够大，则部分位错活动在纳米晶材料中占据主导地位。理想晶体结构的分布沿着径向几乎保持不变，这证明了引起的横向变形很小。动画显示许多原子被压头的进给剥离。这种类型的原子去除（就像雨流一样移动）不同于宏观尺度上的任何类型的材料剥离。因此，衬底的变形是由位错和原子滑动耦合产生的。位错分布更适合于表征材料小尺度变形。此外，观察到一种新的锥形位错分布。随着刀具进给量的增加，螺位错量逐渐增加，刃位错量逐渐减少。模拟结果还表明，晶界表现出比理想晶格更高的自扩散系数，这有助于晶界滑动。
A comprehensive understanding of the basic deformation mechanisms is essential for novel nanomaterials with unique properties for engineering applications. Unfortunately, nanopolycrystal materials with smaller grains are difficult prepare, which makes the study of the deformation process difficult using experiments. The molecular dynamics (MD) method has already been proved to be an efficient tool kit for the nanoscale phenomenon and was gradually adopted by many researchers to investigate the mechanical deformation of nanocrystalline materials. This manuscript studies the mechanical response of specimens with internal grains separated by high angle boundaries without porosities and impurities using MD simulation methods. The results demonstrate that the partial dislocation activity takes over in nanocrystalline materials if the grain sizes are large enough. The distribution of the ideal crystal structure along the radial direction remains almost unchanged, which justifies that little lateral deformation is induced. The animation shows that many atoms are stripped by the feeding of the indenter. This type of atom removal (moves just like rain flow) is different from any kind of material stripping in the macroscopic scale. Therefore, the deformation of the substrate is generated by the coupling of dislocation and atom sliding. The distribution of dislocation is more suitable for characterizing materials deformation at small scale. In addition, a novel cone-shaped dislocation distribution is observed. With the feeding of tools, the amount of screw dislocation gradually increases while the amount of the edge dislocation gradually decreases. The simulation results also show that the grain boundary exhibits higher self-diffusivities than the perfect lattice, which is helpful in grain boundary sliding.