Grains and grain boundaries in single-layer graphene atomic patchwork quilts
Grains and grain boundaries in single-layer graphene atomic patchwork quilts
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DOI：
10.1038/nature09718
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发表时间：
2011-01-20
期刊：
影响因子：
64.8
通讯作者：
Muller, David A.
中科院分区：
文献类型：
--
作者：
Huang, Pinshane Y.;Ruiz-Vargas, Carlos S.;Muller, David A.
多晶材料的性质通常由其晶粒的尺寸和其晶界的原子结构决定。这些效应在二维材料中应该特别明显，即使是线缺陷也会分裂和破坏晶体。这些问题在石墨烯中具有实际意义，石墨烯是碳原子的六边形二维晶体。单原子厚的石墨烯片现在可以通过化学气相沉积（1 - 3）在高达米（4）的规模上生产，使其多晶性几乎不可避免。理论上，石墨烯晶界被预测具有明显的电子（5 - 8），磁性（9），化学（10）和机械（11 - 13）性质，这些性质强烈依赖于它们的原子排列。然而，由于晶粒和晶界原子之间的尺寸差为五个数量级，很少有实验充分探索石墨烯的晶粒结构。在这里，我们使用旧的和新的透射电子显微镜技术相结合，以弥合这些长度尺度。使用原子分辨率成像，我们确定的位置和身份的每个原子在晶界上，并发现不同的晶粒缝合在一起，主要是通过五边形-七边形对。我们使用衍射过滤成像（14）来快速绘制数百个晶粒和边界的位置，取向和形状，而不是单独成像每个晶粒中的数十亿个原子，其中以前只有少数报道（15 - 19）。由此产生的图像揭示了一个意想不到的小而复杂的拼凑颗粒连接的倾斜边界。通过将晶粒成像与扫描探针和输运测量相关联，我们表明这些晶界严重削弱了石墨烯膜的机械强度，但不会彻底改变其电性能。这些技术为研究石墨烯等二维材料的结构、性质以及晶粒和晶界的控制打开了新的窗口。
The properties of polycrystalline materials are often dominated by the size of their grains and by the atomic structure of their grain boundaries. These effects should be especially pronounced in two-dimensional materials, where even a line defect can divide and disrupt a crystal. These issues take on practical significance in graphene, which is a hexagonal, two-dimensional crystal of carbon atoms. Single-atom-thick graphene sheets can now be produced by chemical vapour deposition(1-3) on scales of up to metres(4), making their polycrystallinity almost unavoidable. Theoretically, graphene grain boundaries are predicted to have distinct electronic(5-8), magnetic(9), chemical(10) and mechanical(11-13) properties that strongly depend on their atomic arrangement. Yet because of the five-order-of-magnitude size difference between grains and the atoms at grain boundaries, few experiments have fully explored the graphene grain structure. Here we use a combination of old and new transmission electron microscopy techniques to bridge these length scales. Using atomic-resolution imaging, we determine the location and identity of every atom at a grain boundary and find that different grains stitch together predominantly through pentagon-heptagon pairs. Rather than individually imaging the several billion atoms in each grain, we use diffraction-filtered imaging(14) to rapidly map the location, orientation and shape of several hundred grains and boundaries, where only a handful have been previously reported(15-19). The resulting images reveal an unexpectedly small and intricate patchwork of grains connected by tilt boundaries. By correlating grain imaging with scanning probe and transport measurements, we show that these grain boundaries severely weaken the mechanical strength of graphene membranes but do not as drastically alter their electrical properties. These techniques open a new window for studies on the structure, properties and control of grains and grain boundaries in graphene and other two-dimensional materials.