石墨烯在云母上的粘附：表面形态的作用
Graphene adhesion on mica: Role of surface morphology
摘要：
本文采用密度泛函理论（DFT）和考虑vdW相互作用（vdW-DF方法）的方法研究了石墨烯在白云母表面的粘附性和电子性质.我们发现，不规则的局部结构的分裂云母表面提供不同的机制云母-石墨烯结合。通过假设两个表面的电中性，结合主要是vdW性质，在室温下几乎不超过每个碳原子的热能。相反，如果钾原子不均匀地分布在云母上，则表面的不同区域引起石墨烯的$n$型或$p$型掺杂。反过来，在表面之间产生额外的相互作用，显著增加粘附力。对于每种情况，石墨烯的电子状态保持不变的粘附。然而，可以预期的是，由于电荷掺杂的不对称性，支撑在实际云母上的石墨烯的费米能级可以相对于狄拉克点移动。石墨烯和云母之间的距离为不同区域的表面的变化被发现是一致的，与最近的原子力显微镜实验。云母的相对平坦性和云母-石墨烯系统中不存在层间共价键合使得这一对成为实际应用的有希望的候选者。
英文摘要：
We investigate theoretically the adhesion and electronic properties of graphene on a muscovite mica surface using the density functional theory (DFT) with van der Waals (vdW) interactions taken into account (the vdW-DF approach). We found that irregularities in the local structure of cleaved mica surface provide different mechanisms for the mica-graphene binding. By assuming electroneutrality for both surfaces, the binding is mainly of vdW nature, barely exceeding thermal energy per carbon atom at room temperature. In contrast, if potassium atoms are non uniformly distributed on mica, the different regions of the surface give rise to $n$- or $p$-type doping of graphene. In turn, an additional interaction arises between the surfaces, significantly increasing the adhesion. For each case the electronic states of graphene remain unaltered by the adhesion. It is expected, however, that the Fermi level of graphene supported on realistic mica could be shifted relative to the Dirac point due to asymmetry in the charge doping. Obtained variations of the distance between graphene and mica for different regions of the surface are found to be consistent with recent atomic force microscopy experiments. A relative flatness of mica and the absence of interlayer covalent bonding in the mica-graphene system make this pair a promising candidate for practical use.
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