Influence of nanometre‐sized notch and water on the fracture behaviour of single crystal silicon microelements
Influence of nanometre‐sized notch and water on the fracture behaviour of single crystal silicon microelements
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纳米缺口和水对单晶硅微元件断裂行为的影响
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
K. Komai
中科院分区：
文献类型：
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作者：
K. Minoshima;T. Terada;K. Komai
本文研究了缺口和水环境对单晶硅微元件准静态和疲劳断裂行为的影响。测试在光滑和缺口微悬臂梁样品中进行。通过对（110）硅晶片进行微机械加工（光刻）制备光滑样品。对于一些试样，通过使用聚焦离子束系统，在距离样品根部100 μ m处加工出纳米尺寸的缺口。优化了加工条件，成功地引入了V形切口。通过原子力显微镜（AFM）测量的凹口的曲率半径随着凹口深度的增加而减小，并且范围从约20至100 nm。单晶Si微元发生弹性变形直至最终失效，其性质为脆性。光滑的微悬臂梁试样的最大断裂强度达到约7.7 GPa，这是高于在毫米级的单晶Si样品中获得的。然而，断裂强度随着切口深度的增加而降低，即使切口深度为纳米量级，这意味着通常被认为是普通尺寸机械部件中的表面粗糙度的纳米深切口导致Si微量元素的断裂强度降低。断裂起始于缺口处，然后{111}裂纹沿垂直于样品表面的方向扩展。疲劳试验也在实验室空气和纯水中进行，应力循环频率为0.1 Hz，应力比为0.1。在实验室空气中，没有观察到疲劳损伤，即使表面的AFM纳米检查。然而，当在纯水中进行疲劳试验时，水中的疲劳寿命降低。动载和水环境的协同作用促进了{111}面上裂纹的形成。原子力显微镜能够成像纳米级的裂缝，这导致了在水中的失败。
The influence of a notch and a water environment on the quasi-static and fatigue fracture behaviour was investigated in single crystal silicon microelements. The tests were conducted in smooth and notched microcantilever beam samples. Smooth specimens were prepared by micromachining (photo-etching) of (110) silicon wafers. For some specimens, a nanometre-sized notch was machined 100 pm away from the sample root by using a focused ion beam system. A machining condition was optimized, and the V-shaped notch was successfully introduced. The radius of curvature of the notch, measured by an atomic force microscope (AFM), decreased with an increase in notch depth, and ranged from about 20 to 100 nm. Single-crystal Si microelements deformed elastically until final failure, which was of a brittle nature. The maximum fracture strength of a smooth microcantilever specimen reached about 7.7 GPa, which was higher than that obtained in millimetre-sized single crystal Si samples. However, the fracture strength decreased with an increase in notch depth, even though the notch depth was of the order of a nanometre, This means that a nanometre deep notch, which is often regarded as surface roughness in ordinary-sized mechanical components, caused a decrease in the fracture strength of Si microelements. The fracture initiated at the notch, and then the {111} crack propagated in the direction normal to the sample surface. Fatigue tests were also conducted in laboratory air and in pure water at a stress cycle frequency of 0.1 Hz and a stress ratio of 0.1. In laboratory air, no fatigue damage was observed even though the surface was nanoscopically examined by an AFM. However, when the fatigue tests were conducted in pure water, the fatigue lives in water were decreased. Crack formation on the {111} plane was promoted by a synergistic effect of the dynamic loading and the water environment. Atomic force microscopy was capable of imaging the nanoscopic cracks, which caused failure in water.