Deep sub-{\AA}ngstrom imaging of 2D materials with a high dynamic range detector

TL;DR

This paper introduces a novel electron microscopy technique combining a high dynamic range detector and ptychography, achieving near-atomic resolution of 2D materials at lower beam energies, surpassing traditional lens limitations.

Contribution

The study demonstrates a new imaging approach that significantly improves spatial resolution of 2D materials beyond conventional limits using advanced detector technology and phase retrieval methods.

Findings

Achieved ~0.39 Å resolution at 80 keV beam energy.

Enhanced contrast of single-atom defects in MoS2.

Surpassed traditional lens resolution limits using ptychography.

Abstract

Aberration-corrected optics have made electron microscopy at atomic-resolution a widespread and often essential tool for nanocharacterization. Image resolution is dominated by beam energy and the numerical aperture of the lens ({\alpha}), with state-of-the-art reaching ~0.47 {\AA} at 300 keV. Two-dimensional materials are imaged at lower beam energies to avoid knock-on damage, limiting spatial resolution to ~1 {\AA}. Here, by combining a new electron microscope pixel array detector with the dynamic range to record the complete distribution of transmitted electrons and full-field ptychography to recover phase information from the full phase space, we increased the spatial resolution well beyond the traditional lens limitations. At 80 keV beam energy, our ptychographic reconstructions significantly improved image contrast of single-atom defects in MoS2, reaching an information limit close to 5{\alpha}, corresponding to a 0.39 {\AA} Abbe resolution, at the same dose and imaging conditions where conventional imaging modes reach only 0.98 {\AA}.