Max-Planck-Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
Nano Lett. 2010 Nov 10;10(11):4544-8. doi: 10.1021/nl102526s. Epub 2010 Oct 14.
Theory has predicted rich and very distinct physics for graphene devices with boundaries that follow either the armchair or the zigzag crystallographic directions. A prerequisite to disclose this physics in experiment is to be able to produce devices with boundaries of pure chirality. Exfoliated flakes frequently exhibit corners with an odd multiple of 30°, which raised expectations that their boundaries follow pure zigzag and armchair directions. The predicted Raman behavior at such crystallographic edges however failed to confirm pure edge chirality. Here, we perform confocal Raman spectroscopy on hexagonal holes obtained after the anisotropic etching of prepatterned pits using carbothermal decomposition of SiO(2). The boundaries of the hexagonal holes are aligned along the zigzag crystallographic direction and leave hardly any signature in the Raman map indicating unprecedented purity of the edge chirality. This work offers the first opportunity to experimentally confirm the validity of the Raman theory for graphene edges.
理论预测了具有沿扶手椅或锯齿形晶体方向的边界的石墨烯器件的丰富而非常独特的物理性质。在实验中揭示这种物理性质的前提条件是能够制造出具有纯手性边界的器件。剥落的薄片经常表现出具有奇数 30°倍数的角，这使得人们期望它们的边界遵循纯锯齿形和扶手椅方向。然而，在这种晶体边缘处预测的拉曼行为未能证实纯边缘手性。在这里，我们使用 SiO2 的碳热分解，在使用各向异性刻蚀预先图案化的凹坑后获得的六方孔上进行共焦拉曼光谱。六方孔的边界沿锯齿形晶体方向排列，在拉曼图谱中几乎没有留下任何痕迹，表明边缘手性的空前纯度。这项工作首次提供了实验证实石墨烯边缘拉曼理论有效性的机会。
