Thomsen Joachim Dahl, Wang Yaxian, Flyvbjerg Henrik, Park Eugene, Watanabe Kenji, Taniguchi Takashi, Narang Prineha, Ross Frances M
Division of Physical Sciences, College of Letters and Science, University of California, Los Angeles, CL 90095, USA.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Adv Mater. 2024 Sep;36(39):e2403989. doi: 10.1002/adma.202403989. Epub 2024 Aug 4.
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/WSe, 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.
扩散过程控制着诸如范德华（vdW）键合材料中的相变、掺杂和嵌入等基本现象。在此，通过记录扫描透射电子显微镜电影，对在三种不同的vdW界面（六方氮化硼（BN）/真空、BN/BN和BN/WSe）处单个原子的运动进行可视化，从而量化了W原子的扩散动力学。在密度泛函理论（DFT）计算的支持下，推断出在所有情况下，扩散都受电子束产生的缺陷位点处的间歇性捕获控制。这导致扩散特性强烈依赖于缺陷数量。这些结果表明，vdW材料中的扩散和嵌入过程具有高度可调性，并且对晶体质量敏感。以高空间和时间分辨率对vdW异质结构内部的层和单个原子进行成像，为直接可视化扩散和原子相互作用以及探索原子结构、其原位修饰以及结合原子分辨率成像的有源器件电学性质测量的实验提供了可能性。
