Direct Visualization of Defect‐Controlled Diffusion in van der Waals Gaps

• Published in: Advanced materials (Weinheim) 2024-09, Vol.36 (39), p.e2403989-n/a
• Main Authors: Thomsen, Joachim Dahl, Wang, Yaxian, Flyvbjerg, Henrik, Park, Eugene, Watanabe, Kenji, Taniguchi, Takashi, Narang, Prineha, Ross, Frances M.
• Format: Article
• Language: English
• Subjects: 2D materials; Atomic interactions; Atomic properties; Atomic structure; Boron nitride; Chemical bonds; Crystal defects; Density functional theory; DFT calculations; diffusion; Diffusion layers; Electron beams; Heterostructures; Intercalation; Phase transitions; Scanning transmission electron microscopy; Temporal resolution; transmission electron microscopy; van der Waals heterostructures; Visualization
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202403989

Diffusion processes govern fundamental phenomena such as phase transformations, doping, and intercalation in van der Waals (vdW) bonded materials. Here, the diffusion dynamics of W atoms by visualizing the motion of individual atoms at three different vdW interfaces: hexagonal boron nitride (BN)/vacuum, BN/BN, and BN/WSe2, by recording scanning transmission electron microscopy movies is quantified. Supported by density functional theory (DFT) calculations, it is inferred that in all cases diffusion is governed by intermittent trapping at electron beam‐generated defect sites. This leads to diffusion properties that depend strongly on the number of defects. These results suggest that diffusion and intercalation processes in vdW materials are highly tunable and sensitive to crystal quality. The demonstration of imaging, with high spatial and temporal resolution, of layers and individual atoms inside vdW heterostructures offers possibilities for direct visualization of diffusion and atomic interactions, as well as for experiments exploring atomic structures, their in situ modification, and electrical property measurements of active devices combined with atomic resolution imaging. W atom diffusion at van der Waals (vdW) interfaces (BN/WSe2, BN/BN), and on BN surfaces using scanning transmission electron microscopy is visualized. Diffusion is in all cases is governed by intermittent trapping at electron beam‐generated defect sites, suggesting processes that are highly tunable and sensitive to crystal quality. This enables direct visualization of atomic interactions and materials inside vdW heterostructures.