How many detector pixels do we need for super-resolution ptychography?

To overcome the spatial resolution limit set by aperture-limited diffraction in traditional scanning transmission electron microscopy (STEM), microscopists have developed ptychography enabled by iterative phase retrieval algorithms and high-dynamic-range pixel array detectors. However, the state-of-the-art detectors with thousands of pixels for acquiring full scattering distribution required for ptychography reconstructions suffer from relatively slow acquisition speed compared to differential phase contrast (DPC) imaging with 2x2 pixels, and the slower acquisitions lead to more severe scan noise, drift, and damage. Here, we demonstrated that super-resolution is still possible with only 2x2 detector pixels with increased real space sampling and that the ptychography can significantly outperform the conventional DPC analysis. We optimized experimental and reconstruction parameters through simulated datasets and performed experiments on WSe₂/MoS₂ bilayer Moiré patterns with 2x2 pixels DPC detectors. We successfully achieved super-resolution ptychography reconstruction with rapid acquisition conditions (25pA and only 1µs dwell time) using segmented detectors.