Integral to the exploration of nonequilibrium phenomena in solid-state systems is the study of lattice motion after photoexcitation by a femtosecond laser pulse. For the past two decades, ultrafast electron diffraction (UED) has played a critical role in this regard. Despite remarkable progress in instrumental development, this technique is still bottlenecked by a demanding sample preparation process, where ultrathin single crystals of large lateral size are typically required. In this work, we describe an efficient, versatile method that yields high-quality, laterally extended (≥ 100 µm), and thin (≤ 50 nm) single crystals on amorphous films of Si₃N₄ windows. It applies to most exfoliable materials, including those reactive in ambient conditions, and promises clean, flat surfaces. Besides the natural extension to fabricating van der Waals heterostructures, our method can also be applied to future-generation UED that enables additional control of sample parameters, such as electrostatic gating and excitation by a locally enhanced terahertz field. Our work significantly expands the type of samples for UED studies and also finds application in other time-resolved techniques such as attosecond extreme-ultraviolet absorption spectroscopy. This method hence provides further opportunities to explore photoinduced transitions and to discover novel states of matter out of equilibrium.

对固态系统中非平衡现象的探索不可或缺的是研究飞秒激光脉冲光激发后的晶格运动。在过去的二十年中，超快电子衍射 (UED) 在这方面发挥了关键作用。尽管在仪器开发方面取得了显着进展，但该技术仍然受到要求苛刻的样品制备过程的阻碍，其中通常需要大横向尺寸的超薄单晶。在这项工作中，我们描述了一种高效、通用的方法，可在 Si ₃ N ₄非晶薄膜上产生高质量、横向扩展 (≥ 100 µm) 和薄 (≤ 50 nm) 的单晶视窗。它适用于大多数可剥落材料，包括那些在环境条件下具有反应性的材料，并承诺清洁、平坦的表面。除了制造范德华异质结构的自然延伸外，我们的方法还可以应用于下一代 UED，从而能够对样品参数进行额外控制，例如通过局部增强的太赫兹场进行静电门控和激发。我们的工作显着扩展了 UED 研究的样品类型，并且还发现了其他时间分辨技术的应用，例如阿秒极紫外吸收光谱。因此，该方法提供了进一步的机会来探索光致跃迁和发现物质的新的失衡状态。