Reliable phase quantification in focused probe electron ptychography of thin materials

TL;DR

This paper introduces a new method for accurately quantifying atomic site phases in focused probe electron ptychography of thin materials, overcoming halo effects and robust to experimental variations.

Contribution

A novel quantification approach that addresses halo effects in atomic phase measurements, improving accuracy in 2D material analysis.

Findings

Effective phase quantification despite halo effects

Robustness to noise and sample tilt

Enhanced sensitivity to charge transfer phenomena

Abstract

Electron ptychography provides highly sensitive, dose efficient phase images which can be corrected for aberrations after the data has been acquired. This is crucial when very precise quantification is required, such as with sensitivity to charge transfer due to bonding. Drift can now be essentially eliminated as a major impediment to focused probe ptychography, which benefits from the availability of easily interpretable simultaneous Z-contrast imaging. However challenges have remained when quantifying the ptychographic phases of atomic sites. The phase response of a single atom has a negative halo which can cause atoms to reduce in phase when brought closer together. When unaccounted for, as in integrating methods of quantification, this effect can completely obscure the effects of charge transfer. Here we provide a new method of quantification that overcomes this challenge, at least for 2D materials, and is robust to experimental parameters such as noise, sample tilt.