Imaging Dual-Moiré Lattices in Twisted Bilayer Graphene Aligned on Hexagonal Boron Nitride Using Microwave Impedance Microscopy,Nano Letters

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Imaging Dual-Moiré Lattices in Twisted Bilayer Graphene Aligned on Hexagonal Boron Nitride Using Microwave Impedance Microscopy
Nano Letters ( IF 9.6 ) Pub Date : 2021-05-05 , DOI: 10.1021/acs.nanolett.1c00601
Xiong Huang _{1,

2} , Lingxiu Chen ₃ , Shujie Tang ₄ , Chengxin Jiang ₅ , Chen Chen ₅ , Huishan Wang ₅ , Zhi-Xun Shen ₆ , Haomin Wang ₅ , Yong-Tao Cui ₁

Affiliation

Moiré superlattices (MSLs) formed in van der Waals materials have become a promising platform to realize novel two-dimensional electronic states. Angle-aligned trilayer structures can form two sets of MSLs which could potentially interfere. In this work, we directly image the moiré patterns in both monolayer and twisted bilayer graphene aligned on hexagonal boron nitride (hBN), using combined scanning microwave impedance microscopy and conductive atomic force microscopy. Correlation of the two techniques reveals the contrast mechanism for the achieved ultrahigh spatial resolution (<2 nm). We observe two sets of MSLs with different periodicities in the trilayer stack. The smaller MSL breaks the 6-fold rotational symmetry and exhibits abrupt discontinuities at the boundaries of the larger MSL. Using a rigid atomic-stacking model, we demonstrate that the hBN layer considerably modifies the MSL of twisted bilayer graphene. We further analyze its effect on the reciprocal space spectrum of the dual-moiré system.

中文翻译：

使用微波阻抗显微镜对六角双层氮化硼上排列的扭曲双层石墨烯中的双莫尔格子成像。

用范德华材料形成的莫尔超晶格（MSL）已成为实现新颖的二维电子态的有前途的平台。角度对齐的三层结构可以形成两组MSL，这些MSL可能会产生干扰。在这项工作中，我们使用组合扫描微波阻抗显微镜和导电原子力显微镜，直接成像排列在六方氮化硼（hBN）上的单层和扭曲双层石墨烯中的莫尔图案。两种技术的相关性揭示了实现超高空间分辨率（<2 nm）的对比机制。我们在三层堆栈中观察到两组具有不同周期性的MSL。较小的MSL破坏了6倍的旋转对称性，并在较大的MSL的边界处表现出突然的不连续性。使用刚性原子堆积模型，我们证明了hBN层极大地改变了扭曲双层石墨烯的MSL。我们进一步分析了它对双莫尔系统的倒数空间谱的影响。

更新日期：2021-05-26

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