Nature Communications ( IF 14.7 ) Pub Date : 2024-03-21 , DOI: 10.1038/s41467-024-46934-0
Hongguang Wang 1 , Jiawei Zhang 1 , Chen Shen 2 , Chao Yang 1 , Kathrin Küster 1 , Julia Deuschle 1 , Ulrich Starke 1 , Hongbin Zhang 2 , Masahiko Isobe 1 , Dennis Huang 1 , Peter A van Aken 1 , Hidenori Takagi 1, 3, 4
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Two-dimensional (2D) van der Waals (vdW) materials offer rich tuning opportunities generated by different stacking configurations or by introducing intercalants into the vdW gaps. Current knowledge of the interplay between stacking polytypes and intercalation often relies on macroscopically averaged probes, which fail to pinpoint the exact atomic position and chemical state of the intercalants in real space. Here, by using atomic-resolution electron energy-loss spectroscopy in a scanning transmission electron microscope, we visualize a stacking-selective self-intercalation phenomenon in thin films of the transition-metal dichalcogenide (TMDC) Nb1+xSe2. We observe robust contrasts between 180°-stacked layers with large amounts of Nb intercalants inside their vdW gaps and 0°-stacked layers with little detectable intercalants inside their vdW gaps, coexisting on the atomic scale. First-principles calculations suggest that the films lie at the boundary of a phase transition from 0° to 180° stacking when the intercalant concentration x exceeds ~0.25, which we could attain in our films due to specific kinetic pathways. Our results offer not only renewed mechanistic insights into stacking and intercalation, but also open up prospects for engineering the functionality of TMDCs via stacking-selective self-intercalation.
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外延 Nb1+xSe2 薄膜中堆叠选择性自插层的直接可视化
二维 (2D) 范德华 (vdW) 材料提供了丰富的调节机会,这些机会是通过不同的堆叠配置或通过在 vdW 间隙中引入嵌入剂而产生的。目前对堆叠多型体和插层之间相互作用的了解通常依赖于宏观平均探针,而这种探针无法精确定位真实空间中插层剂的确切原子位置和化学状态。在这里,通过在扫描透射电子显微镜中使用原子分辨率电子能量损失光谱,我们观察到过渡金属二硫属化物(TMDC)Nb 1+ x Se 2薄膜中的堆叠选择性自插层现象。我们观察到 vdW 间隙内有大量 Nb 嵌入剂的 180° 堆叠层和 vdW 间隙内几乎没有可检测到的嵌入剂的 0° 堆叠层之间存在强烈对比,这两种层在原子尺度上共存。第一原理计算表明,当插层剂浓度x超过 ~0.25 时,薄膜位于从 0° 到 180° 堆叠的相变边界,由于特定的动力学途径,我们可以在薄膜中实现这一目标。我们的研究结果不仅为堆叠和嵌入提供了新的机制见解,而且还为通过堆叠选择性自嵌入来设计 TMDC 的功能开辟了前景。