In Situ Nano-thermomechanical Experiment Reveals Brittle to Ductile Transition in Silicon Nanowires
In Situ Nano-thermomechanical Experiment Reveals Brittle to Ductile Transition in Silicon Nanowires
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DOI：
10.1021/acs.nanolett.9b01789
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发表时间：
2019-08-01
期刊：
影响因子：
10.8
通讯作者：
Zhu, Yong
中科院分区：
文献类型：
--
作者：
Cheng, Guangming;Zhang, Yin;Zhu, Yong
硅（Si）纳米结构广泛应用于微电子和纳米技术中。纳米硅的脆韧转变是一个科学和技术上的热点问题，但这一现象及其机制至今仍不清楚。通过在透射电子显微镜（TEM）内进行原位温度控制的纳米力学测试，在这里，我们表明，在拉伸下的结晶硅纳米线在室温下是脆性的，但在高温下表现出韧性行为与位错介导的塑性。我们发现，减小纳米线直径促进了位错介导的响应，如在室温和600 K之间测试的78根Si纳米线所示。原位高分辨率TEM成像和原子反应途径模型显示，非常规的1/2 < 110 >{001}位错随着温度的升高变得高度活跃，因此在变形带的形成中起着关键作用，导致Si纳米线在高温下从脆性断裂转变为位错介导的失效。这项研究提供了定量表征和机制的见解脆韧性转变的硅纳米结构。
Silicon (Si) nanostructures are widely used in microelectronics and nanotechnology. Brittle to ductile transition in nanoscale Si is of great scientific and technological interest but this phenomenon and its underlying mechanism remain elusive. By conducting in situ temperature-controlled nanomechanical testing inside a transmission electron microscope (TEM), here we show that the crystalline Si nanowires under tension are brittle at room temperature but exhibit ductile behavior with dislocation-mediated plasticity at elevated temperatures. We find that reducing the nanowire diameter promotes the dislocation-mediated responses, as shown by 78 Si nanowires tested between room temperature and 600 K In situ high-resolution TEM imaging and atomistic reaction pathway modeling reveal that the unconventional 1/2 < 110 >{001} dislocations become highly active with increasing temperature and thus play a critical role in the formation of deformation bands, leading to transition from brittle fracture to dislocation-mediated failure in Si nanowires at elevated temperatures. This study provides quantitative characterization and mechanistic insight for the brittle to ductile transition in Si nanostructures.