On the Origin of Nonclassical Ripples in Draped Graphene Nanosheets: Implications for Straintronics
On the Origin of Nonclassical Ripples in Draped Graphene Nanosheets: Implications for Straintronics
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DOI：
10.1021/acsanm.2c02137
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发表时间：
2022-07-26
影响因子：
5.9
通讯作者：
Hudson, E. W.
中科院分区：
文献类型：
--
作者：
Banerjee, Riju;Granzier-Nakajima, Tomotaroh;Hudson, E. W.
自从石墨烯的发现以及随后对单原子厚度材料的兴趣爆发以来，研究其机械性能一直是一个活跃的研究领域。原子长度尺度通常需要重新思考物理定律，使得此类研究对于理解和最终利用材料特性至关重要。在这里，我们报告了通过扫描隧道显微镜和原子尺度模拟对悬浮单层石墨烯片中纳米级周期性波纹的研究。与经典织物中发现的正弦波纹不同，我们发现石墨烯形成三角形波纹，其中弯曲仅限于每个波纹顶点处几个晶胞尺寸的狭窄区域。这种非经典的弯曲轮廓导致石墨烯表现得像一种奇怪的织物，无论它如何悬垂，总是以相同的角度弯曲。研究这种非经典机械性能的起源，我们发现与薄的经典织物不同，石墨烯片中会发生面内和面外变形。这两种变形模式相互竞争，从而在覆盖时形成应变锁定的最佳屈曲配置。从电子角度来看，我们看到这种面内变形会产生赝电场，纯粹通过应变调制创建类似于 3 nm 宽的 pnp 异质结。
Ever since the discovery of graphene and subsequent explosion of interest in single-atom-thick materials, studying their mechanical properties has been an active area of research. Atomistic length scales often necessitate a rethinking of physical laws, making such studies crucial for understanding and ultimately utilizing material properties. Here, we report on the investigation of nanoscale periodic ripples in suspended, single-layer graphene sheets by scanning tunneling microscopy and atomistic scale simulations. Unlike the sinusoidal ripples found in classical fabrics, we find that graphene forms triangular ripples, where bending is limited to a narrow region on the order of a few unit cell dimensions at the apex of each ripple. This nonclassical bending profile results in graphene behaving like a bizarre fabric, which regardless of how it is draped, always buckles at the same angle. Investigating the origin of such nonclassical mechanical properties, we find that unlike a thin classical fabric, both in-plane and out-of-plane deformations occur in a graphene sheet. These two modes of deformation compete with each other, resulting in a strain-locked optimal buckling configuration when draped. Electronically, we see that this in-plane deformation generates pseudo electric fields creating a similar to 3 nm wide pnp heterojunction purely by strain modulation.