Microscopic Mechanism of Van der Waals Heteroepitaxy in the Formation of MoS2/hBN Vertical Heterostructures

Mitsuhiro Okada; Mina Maruyama; Susumu Okada; Jamie H Warner; Yusuke Kureishi; Yosuke Uchiyama; Takashi Taniguchi; Kenji Watanabe; Tetsuo Shimizu; Toshitaka Kubo; Masatou Ishihara; Hisanori Shinohara; Ryo Kitaura

doi:10.1021/acsomega.0c04168

Microscopic Mechanism of Van der Waals Heteroepitaxy in the Formation of MoS₂/hBN Vertical Heterostructures

ACS Omega. 2020 Nov 30;5(49):31692-31699. doi: 10.1021/acsomega.0c04168. eCollection 2020 Dec 15.

Authors

Affiliations

¹ Nanomaterials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan.
² Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
³ Walker Department of Mechanical Engineering, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas 78712, United States.
⁴ Materials Graduate Program, Texas Materials Institute, The University of Texas at Austin, 204 East Dean Keeton Street, Austin, Texas 78712, United States.
⁵ Department of Chemistry, Nagoya University, Nagoya, Aichi 464-8602, Japan.
⁶ International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.
⁷ Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan.

Abstract

Recent studies have revealed that van der Waals (vdW) heteroepitaxial growth of 2D materials on crystalline substrates, such as hexagonal boron nitride (hBN), leads to the formation of self-aligned grains, which results in defect-free stitching between the grains. However, how the weak vdW interaction causes a strong limitation on the crystal orientation of grains is still not understood yet. In this work, we have focused on investigating the microscopic mechanism of the self-alignment of MoS₂ grains in vdW epitaxial growth on hBN. Using the density functional theory and the Lennard-Jones potential, we found that the interlayer energy between MoS₂ and hBN strongly depends on the size and crystal orientation of MoS₂. We also found that, when the size of MoS₂ is several tens of nanometers, the rotational energy barrier can exceed ∼1 eV, which should suppress rotation to align the crystal orientation of MoS₂ even at the growth temperature.