Moiré Patterns and Electronics Structures of Monolayer MoS₂ on HOPG Studied by Scanning Tunneling Microscopy / Spectroscopy
Chun-I Lu1*, C. Butler2, Y. H. Chu1, H. H. Yang1, Lain-Jong Li3, Minn-Tsong Lin1,3
1Department of Physics, National Taiwan University, Taipei, 106, Taiwan
2Graduate Institute of Applied Physics, National Taiwan University, Taipei, 106, Taiwan
3Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106, Taiwan
* presenting author:呂俊毅,
Transition metal dichalcogenides such as the semiconductor MoS₂ are a class of two-dimensional (2D) crystals which have great potential for technological applications. Many proposed novel devices are based on heterostructures formed between 2D materials, such as MoS₂ and graphene, since the combination of the electronic properties in hybrid heterostructures provides the opportunities to fabricate devices with advanced functionalities. On the other hand, the chemical vapor deposition (CVD) method is a convincing way to develop monolayer MoS₂ ultra-thin film with micro-meter scale and atomically flat. In this report, we grow MoS₂ on HOPG by CVD to form the interface of MoS₂ /graphene, which we investigate using Scanning Tunneling Microscopy /Spectroscopy (STM /S). The moiré pattern analysis shows that the two layers have a potential to align parallel with each other, and that can also explain the specific orientations appearing in the Atomic Force Microscopy (AFM) images. We conclude that since MoS₂ grows at graphite step-edges, the edge structure controls the orientation of the islands. Those growing from zig-zag (or armchair) edges tend to orient with one lattice vector parallel to the bottom layer. From the atomic resolution STS results, the tiny electronic structure difference inside the single domain of moiré pattern or different domains of moiré patterns can also be resolved.

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This project is financially sponsored by Ministry of Science and Technology (MOST 103-2120-M-002-001 ) &(MOST 101-2112-M-002-024-MY3)

Keywords: Scanning Tunneling Microscopy, Moiré patterns, Heterostructures, 2D crystals, Chemical Vapor Deposition