Kimoto Koji, Cretu Ovidiu, Harano Koji, Uesugi Fumihiko, Kikkawa Jun, Aso Kohei, Oshima Yoshifumi, Matsumoto Takashi, Sakuma Yoshiki
Center for Basic Research on Materials, National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan.
Research Center for Autonomous Systems Materialogy, Institute of Integrated Research, Institute of Science Tokyo, Yokohama, 226-8501, Japan.
Small Methods. 2025 Sep;9(9):e01065. doi: 10.1002/smtd.202501065. Epub 2025 Aug 6.
Dichalcogenides, such as molybdenum disulfide (MoS), are being studied extensively due to their 2D feature and various material properties. Although crystal structures are critical for applications, conventional atomic structure analyses have a limited field of view. In this study, the crystal domains of monolayer MoS 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 MoS domains by highlighting the violation of Friedel's law in diffraction physics. Analyses reveal that the specimen deposited on AlO (0001) at 850 °C consists of domains measuring ≈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.
二硫属化物，如二硫化钼（MoS），因其二维特性和各种材料性能而受到广泛研究。尽管晶体结构对应用至关重要，但传统的原子结构分析视野有限。在本研究中，使用四维扫描透射电子显微镜（STEM）和无监督机器学习对通过金属有机化学气相沉积（MOCVD）合成的单层MoS的晶畴进行了分析。通过对来自宽视野的大量（>22k）衍射图案进行非负矩阵分解（NMF）和层次聚类，识别出扭转畴（±11°）。用于检测非中心对称性的预处理通过突出衍射物理学中对弗里德尔定律的违反，有效地可视化了不同MoS畴的极性。分析表明，在850°C下沉积在AlO（0001）上的样品由尺寸约为100nm且具有许多镜面对称孪晶界的畴组成。这些发现为优化MOCVD工艺和阐明晶体生长机制提供了有价值的见解。
