Probing Crystallinity and Grain Structure of 2D Materials and 2D‐Like Van der Waals Heterostructures by Low‐Voltage Electron Diffraction

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2024-01, Vol.221 (1), p.n/a
• Main Authors: Müller, Johannes, Heyl, Max, Schultz, Thorsten, Elsner, Kristiane, Schloz, Marcel, Rühl, Steffen, Seiler, Hélène, Koch, Norbert, List-Kratochvil, Emil J. W., Koch, Christoph T.
• Format: Article
• Language: English
• Subjects: 2D materials; 4D-STEM; 4D-STEM-in-SEM; Atomic structure; Crystal structure; Crystallinity; Diffraction patterns; Electric potential; Electron beams; Electron diffraction; Grain size; Grain structure; Heterostructures; Molybdenum disulfide; Scanning transmission electron microscopy; single crystals; Spatial resolution; Thickness; transmission electron diffraction; Two dimensional materials; Voltage
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202300148

4D scanning transmission electron microscopy (4D‐STEM) is a powerful method for characterizing electron‐transparent samples with down to sub‐Ångstrom spatial resolution. 4D‐STEM can reveal local crystallinity, orientation, grain size, strain, and many more sample properties by rastering a convergent electron beam over a sample area and acquiring a transmission diffraction pattern (DP) at each scan position. These patterns are rich in information about the atomic structure of the probed volume, making this technique a potent tool to characterize even inhomogeneous samples. 4D‐STEM can also be used in scanning electron microscopes (SEMs) by placing an electron‐sensitive camera below the sample. 4D‐STEM‐in‐SEMs is ideally suited to characterize 2D materials and 2D‐like van der Waals heterostructures (vdWH) due to their inherent thickness of a few nanometers. The lower accelerating voltage of SEMs leads to strong scattering even from monolayers. The large field of view and down to sub‐nm spatial resolution of SEMs are ideal to map properties of the different constituents of 2D‐like vdWH by probing their combined sample volume. A unique 4D‐STEM‐in‐SEM system is applied to reveal the single crystallinity of MoS2 exfoliated with gold‐mediation as well as the crystal orientation and coverage of both components of a C60/MoS2 vdWH are determined. 4D scanning transmission electron microscopy (4D‐STEM) can reveal several sample properties including information from different sample layers. 4D‐STEM in scanning electron microscopes (SEM) can be implemented by placing an electron‐sensitive camera below the sample. A unique 4D‐STEM‐in‐SEM system is deployed to show the single crystallinity of MoS2 produced with gold‐mediated exfoliation and both layers of a C60‐MoS2 heterostructure are investigated.