Department of Electrical Engineering and Computer Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Nano Lett. 2013 Apr 10;13(4):1541-8. doi: 10.1021/nl304706j. Epub 2013 Mar 15.
The growth of large-area bilayer graphene has been of technological importance for graphene electronics. The successful application of graphene bilayers critically relies on the precise control of the stacking orientation, which determines both electronic and vibrational properties of the bilayer system. Toward this goal, an effective characterization method is critically needed to allow researchers to easily distinguish the bilayer stacking orientation (i.e., AB stacked or turbostratic). In this work, we developed such a method to provide facile identification of the stacking orientation by isotope labeling. Raman spectroscopy of these isotopically labeled bilayer samples shows a clear signature associated with AB stacking between layers, enabling rapid differentiation between turbostratic and AB-stacked bilayer regions. Using this method, we were able to characterize the stacking orientation in bilayer graphene grown through Low Pressure Chemical Vapor Deposition (LPCVD) with enclosed Cu foils, achieving almost 70% AB-stacked bilayer graphene. Furthermore, by combining surface sensitive fluorination with such hybrid (12)C/(13)C bilayer samples, we are able to identify that the second layer grows underneath the first-grown layer, which is similar to a recently reported observation.
大面积双层石墨烯的生长对于石墨烯电子学具有重要的技术意义。双层石墨烯的成功应用关键依赖于堆叠方向的精确控制，这决定了双层系统的电子和振动性质。为此，需要一种有效的表征方法，以便研究人员能够轻松区分双层的堆叠方向（即 AB 堆叠或乱层堆叠）。在这项工作中，我们开发了一种通过同位素标记来提供简便的堆叠方向识别的方法。这些同位素标记双层样品的拉曼光谱显示出与层间 AB 堆叠相关的清晰特征，能够快速区分乱层和 AB 堆叠的双层区域。使用这种方法，我们能够表征通过带有封闭铜箔的低压化学气相沉积（LPCVD）生长的双层石墨烯的堆叠方向，实现了近 70%的 AB 堆叠双层石墨烯。此外，通过将表面敏感的氟化与这种混合（12）C/（13）C 双层样品结合使用，我们能够确定第二层在第一层下生长，这与最近的一项报道观察结果相似。
