Imaging the electron charge density in monolayer MoS2 at the Ångstrom scale

Abstract

Four-dimensional scanning transmission electron microscopy (4D-STEM) has recently gained widespread attention for its ability to image atomic electric fields with sub-Ångstrom spatial resolution. These electric field maps represent the integrated effect of the nucleus, core electrons and valence electrons, and separating their contributions is non-trivial. In this paper, we utilized simultaneously acquired 4D-STEM center of mass (CoM) images and annular dark field (ADF) images to determine the electron charge density in monolayer MoS2. We find that both the core electrons and the valence electrons contribute to the derived electron charge density. However, due to blurring by the probe shape, the valence electron contribution forms a nearly featureless background while most of the spatial modulation comes from the core electrons. Our findings highlight the importance of probe shape in interpreting charge densities derived from 4D STEM.

References in corpus (5)

• Electron ptychography achieves atomic-resolution limits set by lattice vibrations
• Quantum many-body interactions in digital oxide superlattices
• Revealing the Brønsted-Evans-Polanyi Relation in Halide-Activated Fast MoS2 Growth Towards Millimeter-Sized 2D Crystals
• X-ray imaging of chemically active valence electrons during a pericyclic reaction
• Direct mapping of electronic orbitals in graphene using electron energy-loss spectroscopy

Cited by in corpus (3)

• Detecting charge transfer at defects in 2D materials with electron ptychography
• Quantifying Phase Magnitudes of Open-Source Focused-Probe 4D-STEM Ptychography Reconstructions
• Stacking of charge-density waves in 2H-NbSe${}_2$ bilayers