CBED

Holographic convergent beam electron diffraction (CBED) on 2D materials 

In collaboration with Prof Sarah Haigh (University of Manchester) and Prof Kostya Novoselov (National University of Singapore), we initiated and are developing convergent beam electron diffraction (CBED) performed on two-dimensional (2D) materials [1] and van der Waals structures [2, 3]. 

A CBED pattern a diffraction pattern which is acquired when the sample is probed by a convergent electron beam. Single shot CBED pattern provides information on both, the crystallographic and real space arrangement of atoms. 
    The intensity variations in individual spots are given by the atomic displacements in the probed area. This makes CBED on 2D materials a powerful tool to study structural and stacking defects [4], adsorbates [5], atomic 3D displacements in the layers [1], and the interlayer distances [1, 6]. The formation of the interference patterns in individual CBED spots of 2D crystals can be considered as a hologram [3], thus the adsorbates on graphene can be directly reconstructed from CBED patterns by conventional reconstruction methods adapted from holography [5]. 
    Graphene is the simplest sample to investigate the electron-matter interaction. The intensity distributions in the CBED disks are simply described by single scattering of electron wave by a single layer of carbon atoms. This simplest arrangement allows accurately recover the exact projected potentials (or scattering potentials) of individual carbon atoms directly from the experimental CBED patterns [7].

Convergent beam electron diffraction on 2D materials

References

1. T. Latychevskaia, C. R. Woods, Y. B. Wang, M. Holwill, E. Prestat,S. J. Haigh, K. S. Novoselov, Convergent beam electron holography for analysis of van der Waals heterostructures, PNAS 115, (29), 7473–7478 (2018).
2. T. Latychevskaia, C. R. Woods, Y. B. Wang, M. Holwill, E. Prestat,S. J. Haigh, K. S. Novoselov, Convergent beam electron diffraction of multilayer van der Waals structures, Ultramicroscopy 212, 112976 (2020).
3. T. Latychevskaia, S. J. Haigh, K. S. Novoselov, Holographic convergent electron beam diffraction (CBED) imaging of two-dimensional crystals, Surf. Rev. Lett. 28, (8), 2140001 (2021).
4. T. Latychevskaia, P. Huang, K. S. Novoselov, Imaging defects in two-dimensional crystals by convergent beam electron diffraction, Phys. Rev. B 105, 184113 (2022).
5. T. Latychevskaia, C. R. Woods, Y. B. Wang, M. Holwill, E. Prestat,S. J. Haigh, K. S. Novoselov, Convergent and divergent beam electron holography and reconstruction of adsorbates on free-standing two-dimensional crystals, Front. Phys. 14, (1), 13606 (2019).
6. T. Latychevskaia, Y. Zou, C. R. Woods, Y. B. Wang, M. Holwill, E. Prestat,S. J. Haigh, K. S. Novoselov, Holographic reconstruction of interlayer distance of bilayer two-dimensional crystal samples from their convergent beam electron diffraction patterns, Ultramicroscopy 219, 113020 (2020).
7. T. Latychevskaia, C. R. Woods, Y. B. Wang, M. Holwill, E. Prestat,S. J. Haigh, K. S. Novoselov, Potentials of individual atoms by convergent beam electron diffraction, Carbon 201, 244–250 (2023).