Direct Imaging of Atomic-Scale Ripples in Few-Layer Graphene
Direct Imaging of Atomic-Scale Ripples in Few-Layer Graphene
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DOI：
10.1021/nl300071y
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发表时间：
2012-05-01
期刊：
影响因子：
10.8
通讯作者：
Kaxiras, Efthimios
中科院分区：
文献类型：
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作者：
Wang, Wei L.;Bhandari, Sagar;Kaxiras, Efthimios
石墨烯一直被吹捧为具有非凡稳定性和强度的二维固体的原型。然而，它的存在依赖于理论预测和实验证实的面外波纹。本征波纹的证据已经在互反空间中以展宽的衍射斑点的形式被报道，在这种形式中所有的空间信息都丢失了。在这里，我们展示了使用单色像差校正透射电子显微镜（TEM）在原子尺度上分辨的几层石墨烯（FLG）膜中的波纹的直接实空间图像。FLG的厚度放大了弱涟漪的局部效应，导致空间变化的TEM对比度，这是唯一的反演对称性。在精确的第一性原理散射势计算的基础上，我们比较了特征透射电镜与模拟图像的对比。我们的研究结果描述了真实空间中的波纹，并表明这种特征可能在超薄材料中很常见，甚至在纳米厚度范围内。
Graphene has been touted as the prototypical two-dimensional solid of extraordinary stability and strength. However, its very existence relies on out-of-plane ripples as predicted by theory and confirmed by experiments. Evidence of the intrinsic ripples has been reported in the form of broadened diffraction spots in reciprocal space, in which all spatial information is lost. Here we show direct real-space images of the ripples in a few-layer graphene (FLG) membrane resolved at the atomic scale using monochromated aberration-corrected transmission electron microscopy (TEM). The thickness of FLG amplifies the weak local effects of the ripples, resulting in spatially varying TEM contrast that is unique up to inversion symmetry. We compare the characteristic TEM contrast with simulated images based on accurate first-principles calculations of the scattering potential. Our results characterize the ripples in real space and suggest that such features are likely common in ultrathin materials, even in the nanometer-thickness range.