Band-gap engineering with a twist: Formation of intercalant superlattices in twisted graphene bilayers
Band-gap engineering with a twist: Formation of intercalant superlattices in twisted graphene bilayers
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扭曲的带隙工程：扭曲石墨烯双层中插层超晶格的形成
DOI：
10.1103/physrevb.91.205412
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发表时间：
2015
影响因子：
3.7
通讯作者：
Velimir Meded
中科院分区：
文献类型：
--
作者：
Franz Symalla;Sam Shallcross;Igor Beljakov;Karin Fink;Wolfgang Wenzel;Velimir Meded
长期以来，基于石墨烯的材料一直被认为是新一代高频(太赫兹)电子器件的有前途的构建块，但由于石墨烯本身缺乏固有的带隙，它们的使用变得复杂。在这里，我们利用扭曲的石墨烯双层膜的可控无公度作为碱金属离子插层的支架，使其具有双层超级电池的周期性。对离子随位置变化的能量分布的系统研究表明，碱金属离子的聚集与扭曲双层的对称性成正比。插入的碱金属离子在双层超级电池的水平上充当周期性微扰源，这使得石墨烯的π带之间可以打开和设计带隙。石墨烯层之间的扭曲角决定了插入亚晶格的结构和无序，从而决定了带隙的大小。适当选择插层剂和扭转角，可以在石墨烯中实现带隙工程。我们提出的论点是，插层对石墨烯所有重要的电荷迁移率的影响将相当小。
Graphene-based materials have long been considered as promising building blocks for a new generation of high-frequency (terahertz) electronic devices, but their use is complicated by the lack of an intrinsic band gap in graphene itself. Here we exploit synthetically controllable incommensuration of twisted graphene bilayers as a scaffold for intercalation of alkali metal ions with the periodicity of the bilayer supercell. Systematic exploration of the energy profiles of the ions as a function of position suggests that the alkali metal ions aggregate commensurately with the symmetry of the twisted bilayer. The intercalated alkali metal ions act as a source of a periodic perturbation on the level of the bilayer supercell, which permits opening and engineering of a band gap between graphene's π bands. The twist angle between the graphene layers determines the structure and disorder of the intercalant sublattice and, consequently, the magnitude of the band gap. Appropriate choices of the intercalant and twist angle thus permit band-gap engineering in graphene. We offer arguments that the impact of intercalation on the all important charge mobility of graphene will be rather small.