Effect Mechanism of Nano-scratch Speed on Removal Behavior of Single Crystal Silicon
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摘要: 晶硅作为典型硬脆材料受应变率影响较大,而不同的划擦速度会产生不同的应变率,进而导致不同的去除行为。因此,本文采用分子动力学从应变率的角度研究不同划擦速度下材料的变形与去除过程。结果表明,由于划擦过程中应变率的提高,划擦力、剪切应力和摩擦系数随划擦速度的提高而减小。而划擦温度却随划擦速度的增大而升高,这归因于绝热作用的提升。由于划擦过程中划擦力和摩擦系数的减小,划擦表面轮廓精度和粗糙度随划擦速度的增大而提高。划擦过程中非晶化和相变是单晶硅纳米尺度变形的主要发生机制;剪切应力的减小是造成亚表面损伤层深度随划擦速度升高而减小的主要原因,划擦温度随划擦速度的增大而升高导致了表面非晶层深度的增加。Abstract: As a typical hard and brittle material, single crystal silicon is strongly influenced by strain rate. And different scratching speeds produce different strain rates, which lead to different removal behaviors. Therefore, molecular dynamics was used to study the deformation and removal processes at different scratching speeds from the perspective of strain rate in this paper. The results showed that the scratching force, shear stress and friction coefficient decreased with the increasing scratching speed due to the increase of the strain rate. In contrast, the scratching temperature rose with the increased scratching speed, which was attributed to the elevated adiabatic effect. As the scratching force and friction coefficient decreased during the scratching, the scratching surface profile accuracy and roughness increased with the growing scratching speed. Amorphization and phase transformation were the main occurrence mechanisms for nanoscale deformation of single crystal silicon during scratching. The reduction of shear stress was the main reason why the depth of subsurface damage layer decreased with the rising scratching speed. The increasing scratching temperature induced by increasing scratching speed led to an improvement in the depth of surface amorphous layer.
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Key words:
- single crystal silicon /
- nano-scratch /
- molecular dynamics /
- scratching speed /
- strain rate
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