Achieving sub-0.5-Angstrom resolution ptychography in an uncorrected electron microscope

Abstract: Sub-angstrom resolution has long been limited to aberration-corrected electron microscopy, where it is a powerful tool for understanding the atomic structure and properties of matter.  Here, we demonstrate electron ptychography in an uncorrected scanning transmission electron microscope (STEM) with deep sub-angstrom spatial resolution down to 0.44 Ångstrom, exceeding the conventional resolution of aberration-corrected tools and rivaling their highest ptychographic resolutions. Our approach, which we demonstrate on twisted 2D materials in a widely-available commercial microscope, far surpasses prior ptychographic resolutions (1 to 5 Ångstroms) of uncorrected STEMs.  We further show how geometric aberrations can create optimized, structured beams for dose-efficient electron ptychography. Our results demonstrate that expensive aberration correctors are no longer required for deep sub-angstrom resolution.