Department of Mechanical Engineering and Materials Science, Rice University, Houston, TX 77005, USA.
Proc Natl Acad Sci U S A. 2012 Sep 18;109(38):15136-40. doi: 10.1073/pnas.1207519109. Epub 2012 Sep 4.
The morphology of graphene is crucial for its applications, yet an adequate theory of its growth is lacking: It is either simplified to a phenomenological-continuum level or is overly detailed in atomistic simulations, which are often intractable. Here we put forward a comprehensive picture dubbed nanoreactor, which draws from ideas of step-flow crystal growth augmented by detailed first-principles calculations. As the carbon atoms migrate from the feedstock to catalyst to final graphene lattice, they go through a sequence of states whose energy levels can be computed and arranged into a step-by-step map. Analysis begins with the structure and energies of arbitrary edges to yield equilibrium island shapes. Then, it elucidates how the atoms dock at the edges and how they avoid forming defects. The sequence of atomic row assembly determines the kinetic anisotropy of growth, and consequently, graphene island morphology, explaining a number of experimental facts and suggesting how the growth product can further be improved. Finally, this analysis adds a useful perspective on the synthesis of carbon nanotubes and its essential distinction from graphene.
石墨烯的形态对其应用至关重要，但缺乏充分的生长理论：要么简化为唯象连续体水平，要么在原子模拟中过于详细，而原子模拟往往难以处理。在这里，我们提出了一个全面的图，称为纳米反应器，它借鉴了阶跃流晶体生长的思想，并辅以详细的第一性原理计算。随着碳原子从原料迁移到催化剂到最终的石墨烯晶格，它们经历了一系列的状态，其能级可以被计算出来，并排列成一个逐步的图谱。分析从任意边缘的结构和能量开始，得出平衡岛的形状。然后，它阐明了原子如何在边缘上对接，以及它们如何避免形成缺陷。原子行组装的顺序决定了生长的动力学各向异性，从而决定了石墨烯岛的形态，解释了许多实验事实，并提出了如何进一步改进生长产物。最后，这种分析为碳纳米管的合成提供了一个有用的视角，并说明了它与石墨烯的本质区别。
