Fortin-Deschênes Matthieu, Watanabe Kenji, Taniguchi Takashi, Xia Fengnian
Department of Electrical Engineering, Yale University, New Haven, CT, USA.
Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan.
Nat Mater. 2024 Mar;23(3):339-346. doi: 10.1038/s41563-023-01596-z. Epub 2023 Aug 14.
The unique physics in moiré superlattices of twisted or lattice-mismatched atomic layers holds great promise for future quantum technologies. However, twisted configurations are thermodynamically unfavourable, making accurate twist angle control during growth implausible. While rotationally aligned, lattice-mismatched moirés such as WSe/WS can be synthesized, they lack the critical moiré period tunability, and their formation mechanisms are not well understood. Here, we report the thermodynamically driven van der Waals epitaxy of moirés with a tunable period from 10 to 45 nanometres, using lattice mismatch engineering in two WSSe layers with adjustable chalcogen ratios. Contrary to conventional epitaxy, where lattice-mismatch-induced stress hinders high-quality growth, we reveal the key role of bulk stress in moiré formation and its unique interplay with edge stress in shaping the moiré growth modes. Moreover, the superlattices display tunable interlayer excitons and moiré intralayer excitons. Our studies unveil the epitaxial science of moiré synthesis and lay the foundations for moiré-based technologies.
扭曲或晶格失配的原子层莫尔超晶格中的独特物理性质，为未来量子技术带来了巨大希望。然而，扭曲构型在热力学上是不利的，这使得在生长过程中精确控制扭曲角变得不太可能。虽然可以合成旋转对齐的晶格失配莫尔，如WSe/WS，但它们缺乏关键的莫尔周期可调性，其形成机制也尚未得到很好的理解。在这里，我们报道了通过在具有可调硫族元素比率的两个WSSe层中进行晶格失配工程，实现了周期从10到45纳米可调的莫尔的热力学驱动范德华外延生长。与传统外延生长不同，在传统外延生长中晶格失配引起的应力会阻碍高质量生长，我们揭示了体应力在莫尔形成中的关键作用，以及它与边缘应力在塑造莫尔生长模式方面的独特相互作用。此外，这些超晶格还展示了可调谐的层间激子和莫尔层内激子。我们的研究揭示了莫尔合成的外延科学，并为基于莫尔的技术奠定了基础。
