Strain solitons and topological defects in bilayer graphene
Strain solitons and topological defects in bilayer graphene
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DOI：
10.1073/pnas.1309394110
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发表时间：
2013-07-09
影响因子：
11.1
通讯作者：
McEuen, Paul L.
中科院分区：
文献类型：
--
作者：
Alden, Jonathan S.;Tsen, Adam W.;McEuen, Paul L.
双层石墨烯是近年来研究的热点。层之间的层间注册可以对电子性质产生巨大的影响：例如，在垂直电场的存在下，所谓的贝纳尔堆积石墨烯的电子光谱中出现带隙[Oostinga JB，等人]。(2007)自然材料7：151-157]。这种带隙与双层石墨烯中的结构自发对称性破坏密切相关，其中一个石墨烯层相对于另一个石墨烯层移动了原子间距。这种位移可以在多个方向上发生，导致多个堆积域之间具有孤子状的结构边界。理论家最近提出，在这些边界上存在新的电子态[Vaezi A，et al.(2013年)arxiv：1301.1690；张飞，等人。(2013年)arxiv：1301.4205]，但对它们的结构性质知之甚少。在这里，我们使用电子显微镜以纳米尺度和原子分辨率测量双层石墨烯中孤子边界的宽度、运动和拓扑结构以及相关的拓扑缺陷。我们发现，每个孤子都由发生在6-11 nm范围内的两层石墨烯之间的原子尺度的注册位移组成。我们推导了层间平移的最小能垒，并在1000℃以上的原位加热过程中观察到了孤子运动。这些结构在各种样品中的丰富性及其不同寻常的性质表明，它们将对双层石墨烯的电子和机械性质产生重大影响。
Bilayer graphene has been a subject of intense study in recent years. The interlayer registry between the layers can have dramatic effects on the electronic properties: for example, in the presence of a perpendicular electric field, a band gap appears in the electronic spectrum of so-called Bernal-stacked graphene [Oostinga JB, et al. (2007) Nature Materials 7:151-157]. This band gap is intimately tied to a structural spontaneous symmetry breaking in bilayer graphene, where one of the graphene layers shifts by an atomic spacing with respect to the other. This shift can happen in multiple directions, resulting in multiple stacking domains with soliton-like structural boundaries between them. Theorists have recently proposed that novel electronic states exist at these boundaries [Vaezi A, et al. (2013) arXiv:1301.1690; Zhang F, et al. (2013) arXiv:1301.4205], but very little is known about their structural properties. Here we use electron microscopy to measure with nanoscale and atomic resolution the widths, motion, and topological structure of soliton boundaries and related topological defects in bilayer graphene. We find that each soliton consists of an atomic-scale registry shift between the two graphene layers occurring over 6-11 nm. We infer the minimal energy barrier to interlayer translation and observe soliton motion during in situ heating above 1,000 degrees C. The abundance of these structures across a variety of samples, as well as their unusual properties, suggests that they will have substantial effects on the electronic and mechanical properties of bilayer graphene.