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Research Highlight

Probing Lattice Distortions and Interlayer Spacings of Few-layer 2D Materials

Probing Lattice Distortions and Interlayer Spacings of Few-layer 2D Materials
(a) Annular dark-field scanning transmission electron microscope (ADF-STEM) image of twisted trilayer graphene. (b) Corresponding diffraction pattern (difference between AA-sites and mean) showing interference fringes. Fringe rotation gives an interlayer separation of 7.0 Å for the interfering layers, indicating they are separated by the third layer. (c) Structural distortions in DFT-relaxed twisted bilayer graphene. (d) Interferometric 4D-STEM simulation for structure in (c); amplitude and direction of measured distortions correspond to brightness and color (see inset color wheel), respectively.

Scientific Achievement

A 4D-STEM technique was developed for probing pm-scale, in-plane lattice distortions and for averaging out-of-plane interlayer spacings in stacked and twisted 2D materials.

Significance and Impact

This technique will provide a better understanding of the link between the physical and electronic structures of quantum materials.

Research Details

- The phases of interference fringes in overlapping Bragg disks were used to map pm-scale in-plane lattice distortions in few-layer graphene with nm-scale resolution.

- The interference fringe rotation was used to measure the average interlayer separation of the material.

- Paired DFT calculations and 4D-STEM simulations were used to explore the limits of the technique.

M. J. Zachman, J. Madsen, X. Zhang, P. M. Ajayan, T. Susi, and M. Chi, "Interferometric 4D-STEM for Lattice Distortion and Interlayer Spacing Measurements of Bilayer and Trilayer 2D Materials," Small (2021). DOI: 10.1002/smll.202100388