Molecular dynamics simulation of AFM tip-based hot scratching of nanocrystalline GaAs
Molecular dynamics simulation of AFM tip-based hot scratching of nanocrystalline GaAs
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DOI：
10.1016/j.mssp.2021.105832
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发表时间：
2021-04-08
影响因子：
4.1
通讯作者：
Wang，Yuzhang
中科院分区：
文献类型：
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作者：
Fan，Pengfei;Goel，Saurav;Wang，Yuzhang
GaAs是一种硬脆材料，在室温下切割相当困难，因此本工作探讨了高温条件是否会改善其切割性能。采用分子动力学（MD）模拟了（0 1 0）取向单晶GaAs的原子力显微镜针尖热加工过程。采用600 K、900 K和1200 K（低于熔化温度~1511 K）三个代表性温度切割GaAs，以300 K下的切割性能为基准，使用诸如切割力、动摩擦系数、切割温度、剪切平面角、亚表面损伤深度、切割区剪切应变和金刚石尖端上的应力等指标。较热的条件导致切削力减少25%，然而，动摩擦系数上升了约8%。随着衬底温度的升高，材料去除速率增大，但同时也伴随着衬底亚表面损伤的增加。在300 K的模拟显示了四种主要类型的位错与伯格斯矢量1/2<110>，1/6<112>，<0-11>和1/2<1-12>下的切割区，这些被发现导致韧性响应的锌-砷化镓。最后，发现在热切削过程中发生切屑致密化现象，这是指在低温下切削获得的非晶切削切屑将具有比在较高温度下切削获得的切屑更低的密度。
GaAs is a hard, brittle material and its cutting at room-temperature is rather difficult, so the work explored whether hot conditions improve its cutting performance or not. Atomic force microscope (AFM) tip-based hot machining of the (0 1 0) oriented single crystal GaAs was simulated using molecular dynamics (MD). Three representative temperatures 600 K, 900 K and 1200 K (below the melting temperature of ~1511 K) were used to cut GaAs to benchmark against the cutting performance at 300 K using indicators such as the cutting forces, kinetic coefficient of friction, cutting temperature, shear plane angle, sub-surface damage depth, shear strain in the cutting zone, and stress on the diamond tip. Hotter conditions resulted in the reduction of cutting forces by 25% however, the kinetic coefficient of friction went up by about 8%. While material removal rate was found to increase with the increase of the substrate temperature, it was accompanied by an increase of the sub-surface damage in the substrate. Simulations at 300 K showed four major types of dislocations with Burgers vector 1/2<110>, 1/6<112>, <0–11> and 1/2<1–12> underneath the cutting zone and these were found to cause ductile response in zinc-blende GaAs. Lastly, a phenomenon of chip densification was found to occur during hot cutting which referred to the fact that the amorphous cutting chips obtained from cutting at low temperature will have lower density than the chips obtained from cutting at higher temperatures.