Université Grenoble Alpes, CNRS , I. Néel, F-38000 Grenoble, France.
Nano Lett. 2014 Sep 10;14(9):5044-51. doi: 10.1021/nl5016552. Epub 2014 Aug 14.
We investigate the organized formation of strain, ripples, and suspended features in macroscopic graphene sheets transferred onto corrugated substrates made of an ordered array of silica pillars with variable geometries. Depending on the pitch and sharpness of the corrugated array, graphene can conformally coat the surface, partially collapse, or lie fully suspended between pillars in a fakir-like fashion over tens of micrometers. With increasing pillar density, ripples in collapsed films display a transition from random oriented pleats emerging from pillars to organized domains of parallel ripples linking pillars, eventually leading to suspended tent-like features. Spatially resolved Raman spectroscopy, atomic force microscopy, and electronic microscopy reveal uniaxial strain domains in the transferred graphene, which are induced and controlled by the geometry. We propose a simple theoretical model to explain the structural transition between fully suspended and collapsed graphene. For the arrays of high density pillars, graphene membranes stay suspended over macroscopic distances with minimal interaction with the pillars' apexes. It offers a platform to tailor stress in graphene layers and opens perspectives for electron transport and nanomechanical applications.
我们研究了在由具有不同几何形状的有序二氧化硅柱阵列制成的波纹状基底上转移的宏观石墨烯片上应变、波纹和悬空特征的有组织形成。根据波纹阵列的间距和锐度，石墨烯可以在数十微米的范围内完全覆盖表面，部分坍塌，或者以 fakir 式的方式完全悬空在柱子之间。随着柱密度的增加，坍塌膜中的波纹从从柱子中出现的随机定向褶皱到连接柱子的平行波纹的有组织域转变，最终导致悬空的帐篷状特征。空间分辨拉曼光谱、原子力显微镜和电子显微镜揭示了转移石墨烯中的单轴应变域，这些应变域是由几何形状引起和控制的。我们提出了一个简单的理论模型来解释完全悬空和坍塌石墨烯之间的结构转变。对于高密度柱阵列，石墨烯膜在与柱子顶点最小相互作用的情况下保持在宏观距离上悬空。它为在石墨烯层中调整应力提供了一个平台，并为电子输运和纳米力学应用开辟了前景。
