Naval Research Laboratory, Washington, DC 20007, USA.
ACS Nano. 2013 Jan 22;7(1):637-44. doi: 10.1021/nn304834p. Epub 2012 Dec 14.
Direct, tunable coupling between individually assembled graphene layers is a next step toward designer two-dimensional (2D) crystal systems, with relevance for fundamental studies and technological applications. Here we describe the fabrication and characterization of large-area (>cm(2)), coupled bilayer graphene on SiO(2)/Si substrates. Stacking two graphene films leads to direct electronic interactions between layers, where the resulting film properties are determined by the local twist angle. Polycrystalline bilayer films have a "stained-glass window" appearance explained by the emergence of a narrow absorption band in the visible spectrum that depends on twist angle. Direct measurement of layer orientation via electron diffraction, together with Raman and optical spectroscopy, confirms the persistence of clean interfaces over large areas. Finally, we demonstrate that interlayer coupling can be reversibly turned off through chemical modification, enabling optical-based chemical detection schemes. Together, these results suggest that 2D crystals can be individually assembled to form electronically coupled systems suitable for large-scale applications.
直接、可调谐的单层石墨烯间耦合是向二维（2D）晶体系统设计迈出的下一步，这对基础研究和技术应用都具有重要意义。在此，我们描述了在 SiO2/Si 衬底上大面积（>cm2）、耦合双层石墨烯的制备和表征。堆叠两层石墨烯薄膜会导致层间直接的电子相互作用，其中薄膜的特性由局部扭转角决定。多晶双层薄膜呈现出“彩色玻璃窗”的外观，这是由于在可见光谱中出现了一个窄的吸收带，其依赖于扭转角。通过电子衍射、拉曼和光谱学的直接测量，证实了大面积上清洁界面的稳定性。最后，我们证明通过化学修饰可以可逆地关闭层间耦合，从而实现基于光学的化学检测方案。总之，这些结果表明，2D 晶体可以被单独组装成适合大规模应用的电子耦合系统。
