10nm以下金属与碳纳米管接触时的塑性变形及其机理研究

Whether nanometals and carbon nanotubes can maintain good contact during mechanical motion plays a crucial role in the high-performance operation and reliability of nanoelectromechanical systems. The latest research shows that sub-10-nm metals exhibits liquid-like deformation behavior at room temperature, and its plastic deformation mechanism is dominated by surface diffusion, similar to Coble creep. Research in this area has just begun, leaving a large number of unclear details and unresolved issues. This study intends to utilize Nanofactory STM-TEM operating platform to compress and stretch sub-10-nm metals with carbon nanotubes in a spherical aberration corrected transmission electron microscope. By controlling the strain rate, loading direction, current induced dissolution between carbon nanotube and metals, surface contamination, etc., the dislocation movement, surface diffusion, necking and relaxation process are observed at the atomic scale in real time. The critical size for liquid-like deformation and yield strength for different metals type are obtained. Finally, combined with molecular dynamics simulation, a theoretical framework of plastic deformation will be proposed, which covers the factors such as metal type, strain rate, loading direction, current induced dissolution, surface contamination and other factors. The results will deepen the understanding of plastic deformation in sub-10-nm metals. It is expected to produce flexible carbon nanotube-metal connection that can be used in nanoelectromechanical systems.

纳米金属和碳纳米管能否在机械运动时保持良好的接触，对纳机电系统的高性能运行和可靠性起着至关重要的作用。最新的研究表明：室温下10nm以下金属呈现类液态的变形行为，其塑性变形机制由表面扩散主导，类似于Coble蠕变。这一方面的研究刚刚起步，留有大量不清楚的细节和未解决的问题。本课题拟利用Nanofactory STM-TEM操作平台，在球差校正透射电镜中用碳纳米管挤压拉伸10nm以下金属单体，通过调控应变速率、加载方向、碳纳米管-金属通电互溶、表面污染物等因子，在原子尺度实时观察位错运动、表面扩散、颈缩和弛豫过程，获得不同金属出现类液态变形时的临界尺寸和屈服强度，最后结合分子动力学模拟，给出一个涵盖金属种类、应变速率、加载方向、通电互溶、表面污染物等因素的塑性变形理论框架。课题成果将加深对10nm以下金属塑性变形的理解，并有望制造出基于碳纳米管-金属的柔性连接，应用在纳机电系统中。

随着纳机电系统（Nanoelectromechanical systems, NEMS）和柔性电子学的发展，迫切地需要对纳米器件组成部分的力电性能进行深入研究。纳米金属能否与碳纳米管维持良好的力学电学接触，对NEMS和柔性电子学器件的高性能运行和可靠性至关重要。本项目依托透射电镜和原位功能样品杆，在原子尺度实时观察各种复杂应力条件下金属-碳纳米管界面处的形貌、微结构及成分的变化，部分研究成果以第一作者身份发表论文于碳材料顶级期刊《Carbon》上。项目主要成果包括：（1）制备出表面干净的纳米金属单体，实现了小于10nm纳米金属单体与碳纳米管的挤压、拉伸;（2）获得了通电互溶和外部污染物干扰条件下金属-碳纳米管之间连接的形貌、微结构及成分变化的信息;（3）引入激光脉冲，首次原位观察到纳米金属-碳纳米管界面处的晶态-非晶态转变，并捕捉到了界面处晶核早期生长的瞬态，测试了非晶态物质的热稳定性，对晶态、非晶态物质的成分做电子能量损失谱分析和电子衍射分析，开展了对非晶生成的原因以及重结晶机理的探讨。上述研究结果均可为复杂应力条件下纳机电系统的工作可靠性提供知识储备。