In-plane anisotropy of graphene by strong interlayer interactions with van der Waals epitaxially grown MoO3

Hangyel Kim; Jong Hun Kim; Jungcheol Kim; Jejune Park; Kwanghee Park; Ji-Hwan Baek; June-Chul Shin; Hyeongseok Lee; Jangyup Son; Sunmin Ryu; Young-Woo Son; Hyeonsik Cheong; Gwan-Hyoung Lee

doi:10.1126/sciadv.adg6696

In-plane anisotropy of graphene by strong interlayer interactions with van der Waals epitaxially grown MoO₃

Sci Adv. 2023 Jun 9;9(23):eadg6696. doi: 10.1126/sciadv.adg6696. Epub 2023 Jun 7.

Authors

Hangyel Kim¹, Jong Hun Kim^{1

2}, Jungcheol Kim³, Jejune Park⁴, Kwanghee Park^{5

6}, Ji-Hwan Baek¹, June-Chul Shin¹, Hyeongseok Lee¹, Jangyup Son^{7

8}, Sunmin Ryu⁵, Young-Woo Son⁴, Hyeonsik Cheong³, Gwan-Hyoung Lee¹

Affiliations

¹ Department of Materials Science and Engineering, Seoul National University, Seoul 08826, South Korea.
² Department of Physics, Inha University, Incheon 22212, South Korea.
³ Department of Physics, Sogang University, Seoul 04107, South Korea.
⁴ School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, South Korea.
⁵ Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, South Korea.
⁶ Korea Research Institute of Standards and Science, Daejeon 34113, South Korea.
⁷ Functional Composite Materials Research Center, Korea Institute of Science and Technology (KIST), Jeonbuk 55324, South Korea.
⁸ Division of Nano and Information Technology, KIST School University of Science and Technology (UST), Jeonbuk 55324, South Korea.

Abstract

van der Waals (vdW) epitaxy can be used to grow epilayers with different symmetries on graphene, thereby imparting unprecedented properties in graphene owing to formation of anisotropic superlattices and strong interlayer interactions. Here, we report in-plane anisotropy in graphene by vdW epitaxially grown molybdenum trioxide layers with an elongated superlattice. The grown molybdenum trioxide layers led to high p-doping of the underlying graphene up to p = 1.94 × 10¹³ cm^-2 regardless of the thickness of molybdenum trioxide, maintaining a high carrier mobility of 8155 cm² V^-1 s^-1. Molybdenum trioxide-induced compressive strain in graphene increased up to -0.6% with increasing molybdenum trioxide thickness. The asymmetrical band distortion of molybdenum trioxide-deposited graphene at the Fermi level led to in-plane electrical anisotropy with a high conductance ratio of 1.43 owing to the strong interlayer interaction of molybdenum trioxide-graphene. Our study presents a symmetry engineering method to induce anisotropy in symmetric two-dimensional (2D) materials via the formation of asymmetric superlattices with epitaxially grown 2D layers.