Grubišić-Čabo Antonija, Michiardi Matteo, Sanders Charlotte E, Bianchi Marco, Curcio Davide, Phuyal Dibya, Berntsen Magnus H, Guo Qinda, Dendzik Maciej
Zernike Institute for Advanced Materials, University of Groningen, Groningen, 9747 AG, The Netherlands.
Department of Applied Physics, KTH Royal Institute of Technology, Hannes Alfvéns väg 12, Stockholm, 114 19, Sweden.
Adv Sci (Weinh). 2023 Aug;10(22):e2301243. doi: 10.1002/advs.202301243. Epub 2023 May 26.
2D materials provide a rich platform to study novel physical phenomena arising from quantum confinement of charge carriers. Many of these phenomena are discovered by surface sensitive techniques, such as photoemission spectroscopy, that work in ultra-high vacuum (UHV). Success in experimental studies of 2D materials, however, inherently relies on producing adsorbate-free, large-area, high-quality samples. The method that yields 2D materials of highest quality is mechanical exfoliation from bulk-grown samples. However, as this technique is traditionally performed in a dedicated environment, the transfer of samples into vacuum requires surface cleaning that might diminish the quality of the samples. In this article, a simple method for in situ exfoliation directly in UHV is reported, which yields large-area, single-layered films. Multiple metallic and semiconducting transition metal dichalcogenides are exfoliated in situ onto Au, Ag, and Ge. The exfoliated flakes are found to be of sub-millimeter size with excellent crystallinity and purity, as supported by angle-resolved photoemission spectroscopy, atomic force microscopy, and low-energy electron diffraction. The approach is well-suited for air-sensitive 2D materials, enabling the study of a new suite of electronic properties. In addition, the exfoliation of surface alloys and the possibility of controlling the substrate-2D material twist angle is demonstrated.
二维材料为研究由电荷载流子的量子限域所产生的新型物理现象提供了一个丰富的平台。其中许多现象是通过诸如光电子能谱等在超高真空（UHV）环境下工作的表面敏感技术发现的。然而，二维材料实验研究的成功本质上依赖于制备无吸附质、大面积、高质量的样品。获得最高质量二维材料的方法是从块状生长的样品上进行机械剥离。然而，由于这种技术传统上是在专门的环境中进行的，将样品转移到真空中需要进行表面清洁，这可能会降低样品的质量。在本文中，报道了一种在超高真空中原位剥离的简单方法，该方法可制备大面积的单层薄膜。多种金属和半导体过渡金属二硫属化物在超高真空中原位剥离到金、银和锗上。通过角分辨光电子能谱、原子力显微镜和低能电子衍射证实，剥离的薄片尺寸为亚毫米级，具有优异的结晶度和纯度。该方法非常适合对空气敏感的二维材料，能够研究一系列新的电子特性。此外，还展示了表面合金的剥离以及控制衬底 - 二维材料扭转角的可能性。
