Factors limiting quantitative phase retrieval in atomic-resolution differential phase contrast scanning transmission electron microscopy using a segmented detector

TL;DR

This paper investigates the main factors limiting accurate quantitative phase retrieval in atomic-resolution differential phase contrast STEM using segmented detectors, highlighting the importance of aberration correction and precise parameter characterization.

Contribution

The study identifies key factors affecting phase retrieval accuracy and compares experimental data with simulations to determine which parameters are most critical for reliable results.

Findings

Coherent and incoherent aberrations significantly impact phase accuracy.

Aberration correction is essential for reliable quantitative phase imaging.

Beam deflections coupling to scan introduces artifacts affecting phase interpretation.

Abstract

Quantitative differential phase contrast imaging of materials in atomic-resolution scanning transmission electron microscopy using segmented detectors is limited by various factors, including coherent and incoherent aberrations, detector positioning and uniformity, and scan-distortion. By comparing experimental case studies of monolayer and few-layer graphene with image simulations, we explore which parameters require the most precise characterisation for reliable and quantitative interpretation of the reconstructed phases. Coherent and incoherent lens aberrations are found to have the most significant impact. For images over a large field of view, the impact of noise and non-periodic boundary conditions are appreciable, but in this case study have less of an impact than artefacts introduced by beam deflections coupling to beam scanning (imperfect tilt-shift purity).