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Description:

Dichalcogenides, such as molybdenum disulfide (MoS₂), are being studied extensively due to their two-dimensional feature and various material properties. Although crystal structures are critical for applications, conventional atomic structure analyses have limited field of view. In this study, the crystal domains of monolayer MoS2 synthesized by metal-organic chemical vapor deposition (MOCVD) are analyzed using 4D scanning transmission electron microscopy (STEM) and unsupervised machine learning. Twist domains (±11°) are identified through the nonnegative matrix factorization (NMF) and hierarchical clustering of numerous (>22k) diffraction patterns from a wide field of view. Preprocessing for detecting noncentrosymmetry effectively visualizes the polarities of distinct MoS2 domains by highlighting the violation of Friedel’s law in diffraction physics. Analyses reveal that the specimen deposited on Al2O3 (0001) at 850 °C consists of domains measuring approximately 100 nm in size and featuring many mirror-twin boundaries. The findings provide valuable insights into optimizing the MOCVD process and elucidating crystal growth mechanisms.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: 4D-STEM, dichalcogenide, metal–organic chemical vapor deposition, MoS2,, scanning transmission electron microscopy, unsupervised machine learning

Date published: 2025-08-06

Publisher: Wiley

Journal:

• Small Methods (ISSN: 23669608) e01065

Funding:

• 日本学術振興会 JP22H05145 (学術変革領域研究(A)超セラミックスの高度構造解析)
• 日本学術振興会 JP20H02624 (ソフトマテリアル解析を可能とする電子計数型透過電子顕微鏡法の要素技術開発)
• 日本学術振興会 JP23H04874 (メゾヒエラルキーの映像分子科学)
• 日本学術振興会 JP24K08253 (Development of an intelligent dose-reducing imaging method for the transmission electron microscope)
• 日本学術振興会 JP17H03241 (ＭＯＣＶＤ法による遷移金属ダイカルコゲナイドの成長技術開発とフォトニクス機能探索)
• JST JPMJCR24A3 (ウエハースケールvdWエピタキシーの確立と 2D-CMOS集積化のためのプロセス技術の構築)

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/smtd.202501065

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Updated at: 2025-08-27 12:30:17 +0900

Published on MDR: 2025-08-27 08:19:15 +0900