Title: Strain Anisotropy Driven Spontaneous Formation of Nanoscrolls from Two-Dimensional Janus Layers Show Chinese title

Title: 应变各向异性驱动二维Janus层自发形成纳米卷轴

Abstract: Two-dimensional Janus transition metal dichalcogenides (TMDs) have attracted attention due to their emergent properties arising from broken mirror symmetry and self-driven polarisation fields. While it has been proposed that their vdW superlattices hold the key to achieving superior properties in piezoelectricity and photovoltiacs, available synthesis has ultimately limited their realisation. Here, we report the first packed vdW nanoscrolls made from Janus TMDs through a simple one-drop solution technique. Our results, including ab-initio simulations, show that the Bohr radius difference between the top sulphur and the bottom selenium atoms within Janus M_Se^S (M=Mo, W) results in a permanent compressive surface strain that acts as a nanoscroll formation catalyst after small liquid interaction. Unlike classical 2D layers, the surface strain in Janus TMDs can be engineered from compressive to tensile by placing larger Bohr radius atoms on top (M_S^Se) to yield inverted C scrolls. Detailed microscopy studies offer the first insights into their morphology and readily formed Moir\'e lattices. In contrast, spectroscopy and FETs studies establish their excitonic and device properties and highlight significant differences compared to 2D flat Janus TMDs. These results introduce the first polar Janus TMD nanoscrolls and introduce inherent strain-driven scrolling dynamics as a catalyst to create superlattices. Show Chinese abstract

Abstract: 二维Janus过渡金属二硫属化物（TMDs）因其打破镜像对称性和自驱动极化场而产生的新兴特性而受到关注。 尽管有人提出，它们的范德华超晶格是实现压电和光伏优异性能的关键，但现有的合成方法最终限制了其实现。 在此，我们报告了通过简单的单滴溶液技术首次制备的紧密排列的范德华纳米卷轴。 我们的结果，包括从头算模拟，表明在Janus M_Se^S（M=Mo，W）中，顶部硫原子和底部硒原子之间的玻尔半径差异导致永久的压缩表面应变，在与少量液体相互作用后作为纳米卷轴形成的催化剂。 与经典二维层不同，通过将较大玻尔半径的原子放在顶部（M_S^Se），可以将Janus TMDs中的表面应变从压缩变为拉伸，从而产生倒置的C形卷轴。 详细的显微镜研究提供了对其形态和易于形成的莫里图案的首次见解。 相比之下，光谱学和FETs研究确立了它们的激子和器件特性，并突出了与二维平面Janus TMDs相比的显著差异。 这些结果引入了第一个极性Janus TMD纳米卷轴，并引入了固有应变驱动的滚动动力学作为创建超晶格的催化剂。