University of Oulu

Yu, Z., Dai, Y., Komsa, H.-P., Ren, X., Yuan, M., Xie, M., & Jin, C. (2023). Formation mechanism of mirror twin grain boundaries in molecular beam epitaxy grown monolayer WSe 2 –MoSe 2 lateral heterojunctions. 2D Materials, 10(3), 035010.

Formation mechanism of mirror twin grain boundaries in molecular beam epitaxy grown monolayer WSe₂–MoSe₂ lateral heterojunctions

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Author: Yu, Zhoubin1,2; Dai, Yawei3; Komsa, Hannu-Pekka4;
Organizations: 1State Key Laboratory of Silicon and Advanced Semiconductor Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310024, People's Republic of China
2Jihua Laboratory, Foshan, Guangdong 528200, People's Republic of China
3Physics Department, The University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China
4Microelectronics Research Unit, University of Oulu, 90014 Oulu, Finland
5Hunan Institute of Advanced Sensing and Information Technology, Xiangtan University, Xiangtan, Hunan 411105, People's Republic of China
Format: article
Version: accepted version
Access: embargoed
Persistent link:
Language: English
Published: IOP Publishing, 2023
Publish Date: 2024-05-02


Mirror twin grain boundary (MTB) defects, being a special type of high-symmetry one-dimensional (1D) defects in two-dimensional atomically thin transition metal dichalcogenides (TMDCs), have received considerable interest due to their unique structures and intriguing 1D properties. However, formation and distribution of MTBs in hybrid TMDC materials such as heterojunction remain scarcely studied. Herein, we investigate the spatial distribution, lattice registry and formation mechanism of MTBs in molecular beam epitaxy grown monolayer WSe₂–MoSe₂ lateral heterojunctions using atomic-resolution annular dark-field scanning transmission electron microscopy (ADF-STEM). MTBs manifest a much higher density in MoSe₂ than in WSe₂ domains with a few of them spanning coherently across the domain interface. Compositionally, a Mo-dominant rather than W-dominant configuration was observed in those MTBs located in WSe₂ domains and its origin can be attributed to the preferable Mo substitution to W along the MTBs occurring at the later MoSe₂ growth period. This proposed mechanism is supported by ab-initio density functional theory calculations and substitution dynamics captured by in-situ ADF-STEM. The present study deepens our understanding of MTBs in heterostructured TMDCs, which may also serve as an excellent platform for the exploration of intriguing 1D physics.

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Series: 2D materials
ISSN: 2053-1583
ISSN-E: 2053-1583
ISSN-L: 2053-1583
Volume: 10
Issue: 3
Article number: 035010
DOI: 10.1088/2053-1583/accd06
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Copyright information: © Copyright 2023 IOP Publishing. This is the Accepted Manuscript version of an article accepted for publication in 2D Materials. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at