Ultra-fast Digital DPC Yielding High Spatio-Temporal Resolution for Low-Dose Phase Characterisation

TL;DR

This paper introduces a high-speed digital DPC method that achieves high spatio-temporal resolution in low-dose phase imaging, overcoming data handling challenges in 4D-STEM for in-situ electron microscopy.

Contribution

It demonstrates that digitised DPC signals from simplified detectors can produce reliable phase reconstructions at high speeds, enabling low-dose, high-resolution in-situ imaging.

Findings

Reliable phase reconstruction from digitised signals at high scan speeds

Effective dose fractionation through fast scanning and multi-framing

Overcoming data size challenges with digital signal processing

Abstract

In the scanning transmission electron microscope, both phase imaging of beam-sensitive materials and characterisation of a material's functional properties using in-situ experiments are becoming more widely available. As the practicable scan speed of 4D-STEM detectors improves, so too does the temporal resolution achievable for both differential phase contrast (DPC) and ptychography. However, the read-out burden of pixelated detectors, and the size of the gigabyte to terabyte sized data sets, remain a challenge for both temporal resolution and their practical adoption. In this work, we show that a high-fidelity DPC phase reconstruction can be achieved from both annular segmented detectors or pixelated arrays with relatively few elements using signal digitisation. Unlike conventional analog data, even at the fastest scan speeds, phase reconstructions from digitised DPC-segment images yield reliable data. Finally, dose fractionation by fast scanning and multi-framing allows for post-process binning of frame streams to balance signal-to-noise ratio and temporal resolution for low-dose phase imaging for in-situ experiments.