The structure of suspended graphene sheets
The structure of suspended graphene sheets
复制标题
DOI：
10.1038/nature05545
复制
发表时间：
2007-03-01
期刊：
影响因子：
64.8
通讯作者：
Roth, S.
中科院分区：
文献类型：
--
作者：
Meyer, Jannik C.;Geim, A. K.;Roth, S.
最近石墨烯的发现引起了人们的极大兴趣，到目前为止，人们主要关注这种材料的特殊电子结构，在这种结构中，电荷载流子模仿无质量的相对论粒子(1-3)。然而，石墨烯的物理结构--蜂窝晶格中密集堆积的单层碳原子--也令人费解。一方面，石墨烯似乎是一种严格的二维材料，表现出如此高的晶体质量，以至于电子可以在亚微米距离内传播而不会发生散射。另一方面，根据理论和实验(4-9)，完美的二维晶体不可能在自由态下存在。这种不相容可以通过争辩说，到目前为止研究的所有石墨烯结构都是更大的三维结构的组成部分，要么由块状衬底支撑，要么嵌入三维基质(1-3，9-12)。在这里，我们报告了在真空或空气中自由悬挂在微制支架上的单个石墨烯薄片。这些膜只有一个原子厚，但它们仍然显示出长程结晶有序。然而，我们的透射电子显微镜研究也表明，这些悬浮的石墨烯薄膜并不是完全平坦的：它们表现出内在的微观粗糙，以至于表面法线变化几度，平面外变形达到1 nm。原子薄的单晶膜为基础研究和新技术提供了足够的空间，而在第三维观察到的波纹可能为二维晶体的稳定性提供了微妙的原因(13-15)。
The recent discovery of graphene has sparked much interest, thus far focused on the peculiar electronic structure of this material, in which charge carriers mimic massless relativistic particles(1-3). However, the physical structure of graphene - a single layer of carbon atoms densely packed in a honeycomb crystal lattice - is also puzzling. On the one hand, graphene appears to be a strictly two-dimensional material, exhibiting such a high crystal quality that electrons can travel submicrometre distances without scattering. On the other hand, perfect two-dimensional crystals cannot exist in the free state, according to both theory and experiment(4-9). This incompatibility can be avoided by arguing that all the graphene structures studied so far were an integral part of larger three-dimensional structures, either supported by a bulk substrate or embedded in a three-dimensional matrix(1-3,9-12). Here we report on individual graphene sheets freely suspended on a microfabricated scaffold in vacuum or air. These membranes are only one atom thick, yet they still display long-range crystalline order. However, our studies by transmission electron microscopy also reveal that these suspended graphene sheets are not perfectly flat: they exhibit intrinsic microscopic roughening such that the surface normal varies by several degrees and out-of-plane deformations reach 1 nm. The atomically thin single-crystal membranes offer ample scope for fundamental research and new technologies, whereas the observed corrugations in the third dimension may provide subtle reasons for the stability of two-dimensional crystals(13-15).