Sub-nanometer depth resolution and single dopant visualization achieved by tilt-coupled multislice electron ptychography

TL;DR

This paper introduces a multislice electron ptychography algorithm that achieves sub-nanometer depth resolution and visualizes single dopants in 3D, surpassing previous limitations in electron microscopy.

Contribution

A novel multislice electron ptychography method couples few projections at small tilt angles to significantly enhance depth resolution to sub-nanometer scale.

Findings

Achieved sub-nanometer depth resolution in 3D atomic imaging.

Successfully visualized single dopants and lattice distortions.

Enhanced visibility of light and heavy atoms in electron microscopy.

Abstract

Real-space imaging of three-dimensional atomic structures is a critical yet challenging task in materials science. Although scanning transmission electron microscopy has achieved sub-angstrom lateral resolution through techniques like electron ptychography1,2, depth resolution remains limited to only 2 to 3 nanometers with a single projection setup3,4. Attaining better depth resolution typically necessitates large sample tilt angles and many projections, as seen in atomic electron tomography5,6. Here, we develop a new algorithm based on multislice electron ptychography which couples only a few projections at small tilt angles, but is sufficient to improve the depth resolution by more than threefold to the sub-nanometer scale, and potentially to the atomic level. This technique maintains high resolving power for both light and heavy atoms, and significantly improves the visibility of single dopants. We are thus able to experimentally detect dilute substitutional praseodymium dopants in a brownmillerite oxide, Ca2Co2O5, in three dimensions and observe the accompanying lattice distortion. This technique requires only a moderate level of data acquisition or processing, and can be seamlessly integrated into electron microscopes equipped with conventional components.