Cheng Guangming, Zhang Yin, Chang Tzu-Hsuan, Liu Qunfeng, Chen Lin, Lu Wei D, Zhu Ting, Zhu Yong
Department of Mechanical and Aerospace Engineering , North Carolina State University , Raleigh , North Carolina 27695 , United States.
Woodruff School of Mechanical Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.
Nano Lett. 2019 Aug 14;19(8):5327-5334. doi: 10.1021/acs.nanolett.9b01789. Epub 2019 Jul 23.
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.
硅（Si）纳米结构在微电子和纳米技术中得到广泛应用。纳米尺度硅的脆性到延性转变具有重大的科学和技术意义，但这一现象及其潜在机制仍不清楚。通过在透射电子显微镜（TEM）内进行原位温度控制纳米力学测试，我们在此表明，拉伸状态下的晶体硅纳米线在室温下是脆性的，但在高温下表现出由位错介导的塑性的延性行为。我们发现，减小纳米线直径会促进位错介导的响应，在室温至600 K之间测试的78根硅纳米线表明了这一点。原位高分辨率TEM成像和原子反应路径建模表明，非常规的1/2〈110〉{001}位错随着温度升高变得高度活跃，因此在变形带的形成中起关键作用，导致硅纳米线在高温下从脆性断裂转变为位错介导的失效。这项研究为硅纳米结构中脆性到延性转变提供了定量表征和机理洞察。
