Imaging active topological defects in carbon nanotubes
Imaging active topological defects in carbon nanotubes
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DOI：
10.1038/nnano.2007.141
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发表时间：
2007-06-01
影响因子：
38.3
通讯作者：
Iijima, Sumio
中科院分区：
文献类型：
--
作者：
Suenaga, Kazu;Wakabayashi, Hideaki;Iijima, Sumio
单壁碳纳米管(SWNT)是一层包裹的单层石墨烯，其塑性变形需要活跃的拓扑缺陷--可以沿着纳米管壁迁移的非六角碳环。虽然已用原位电子显微镜研究了单壁碳纳米管1-3的变形，但这些研究只涉及直径的变化，还没有从实验上阐明原子化机理。理论预测，在2000K的拉伸下，单壁碳纳米管中的一些拓扑缺陷可以通过Stone-Wales变换形成，并且可以作为位错核(4，5)。在这里，我们通过具有原子灵敏度的高分辨率(HR)-电子显微镜，首次直接成像了在2,273K加热的单壁碳纳米管中发现的五边形-七角形缺陷对。此外，我们的原位高分辨(HR)-电子显微镜观察显示，在变形的纳米管的扭结附近积累了拓扑缺陷。这一结果表明，位错运动或活跃的拓扑缺陷确实是导致单壁碳纳米管塑性变形的原因。
A single-walled carbon nanotube (SWNT) is a wrapped single graphene layer, and its plastic deformation should require active topological defects-non-hexagonal carbon rings that can migrate along the nanotube wall. Although in situ transmission electron microscopy (TEM) has been used to examine the deformation of SWNTs1-3, these studies deal only with diameter changes and no atomistic mechanism has been elucidated experimentally. Theory predicts that some topological defects can form through the Stone-Wales transformation in SWNTs under tension at 2,000 K, and could act as a dislocation core(4,5). We demonstrate here, by means of high-resolution (HR)-TEM with atomic sensitivity, the first direct imaging of pentagon-heptagon pair defects found in an SWNT that was heated at 2,273 K. Moreover, our in situ HR-TEM observation reveals an accumulation of topological defects near the kink of a deformed nanotube. This result suggests that dislocation motions or active topological defects are indeed responsible for the plastic deformation of SWNTs.