Physics Department, University of Arizona, Tucson, Arizona 85721, USA.
1] Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138, USA [2] School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Nat Mater. 2014 Aug;13(8):786-9. doi: 10.1038/nmat3965. Epub 2014 Apr 28.
The crystal structure of a material plays an important role in determining its electronic properties. Changing from one crystal structure to another involves a phase transition that is usually controlled by a state variable such as temperature or pressure. In the case of trilayer graphene, there are two common stacking configurations (Bernal and rhombohedral) that exhibit very different electronic properties. In graphene flakes with both stacking configurations, the region between them consists of a localized strain soliton where the carbon atoms of one graphene layer shift by the carbon-carbon bond distance. Here we show the ability to move this strain soliton with a perpendicular electric field and hence control the stacking configuration of trilayer graphene with only an external voltage. Moreover, we find that the free-energy difference between the two stacking configurations scales quadratically with electric field, and thus rhombohedral stacking is favoured as the electric field increases. This ability to control the stacking order in graphene opens the way to new devices that combine structural and electrical properties.
材料的晶体结构在决定其电子性质方面起着重要作用。从一种晶体结构转变为另一种晶体结构涉及到相变，通常由温度或压力等状态变量控制。在三层石墨烯的情况下，有两种常见的堆叠构型（伯纳尔和菱面体），它们表现出非常不同的电子性质。在具有两种堆叠构型的石墨烯薄片中，它们之间的区域由局部应变孤子组成，其中一个石墨烯层的碳原子通过碳-碳键距离移动。在这里，我们展示了用垂直电场移动这个应变孤子的能力，从而仅通过外加电压控制三层石墨烯的堆叠构型。此外，我们发现两种堆叠构型之间的自由能差与电场呈二次方关系，因此随着电场的增加，菱面体堆叠更有利。这种控制石墨烯堆叠顺序的能力为结合结构和电气性能的新型器件开辟了道路。
