Optimized conditions for direct imaging of bonding charge density in electron microscopy

TL;DR

This paper demonstrates the potential to observe bonding charge density effects in high-resolution electron microscopy images of Forsterite, highlighting the importance of sample thickness and image processing techniques for detecting subtle bonding contrasts.

Contribution

It introduces optimized imaging conditions and analysis methods to detect valence bonding effects in electron microscopy of mineral samples.

Findings

Bonding effects detectable at 25% intensity level in 20-25 nm thick samples

Dynamical amplification enhances bonding contrast in moderately thick specimens

Exit wave restoration improves observability of bonding charge density

Abstract

We report on the observability of valence bonding effects in aberration-corrected high resolution electron microscopy (HREM) images along the [010] projection of the mineral Forsterite(Mg2SiO4). We have also performed exit wave restorations using simulated noisy images and have determined that both the intensities of individual images and the modulus of the restored complex exit wave are most sensitive to bonding effects at a level of 25% for moderately thick samples of 20-25 nm. This relatively large thickness is due to dynamical amplification of bonding contrast arising from partial de-channeling of 1s states.