The Effect of Intra-Layer Bonding on Electron-Optical Phase Images of Few-Layer WSe2

TL;DR

This paper demonstrates that combining pseudopotentials with all-electron DFT calculations significantly improves the accuracy of simulated electron-optical phase images of few-layer WSe2, aligning them closely with experimental holography data.

Contribution

It introduces a computational approach that enhances simulation accuracy of electron phase images by incorporating bonding effects, surpassing the independent atom approximation.

Findings

Perfect contrast match between experiment and simulation for known thickness samples

Improved atomic-resolution phase distribution in simulations

Method is computationally efficient for large electronic systems

Abstract

The quantitative analysis of electron-optical phase images recorded using off-axis electron holography often relies on the use of computer simulations of electron propagation through a sample. However, simulations that make use of the independent atom approximation are known to overestimate experimental phase shifts by approximately 10%, as they neglect bonding effects. Here, we compare experimental and simulated phase images for few-layer WSe2 . We show that a combination of pseudopotentials and all-electron density functional theory calculations can be used to obtain accurate mean electron phases, as well as improved atomic-resolution spatial distribution of the electron phase. The comparison demonstrates a perfect contrast match between experimental and simulated atomic-resolution phase images for a sample of precisely know thickness. The low computational cost of this approach makes it suitable for the analysis of large electronic systems, including defects, substitutional atoms and material interfaces.