Imaging the potential distribution of individual charged impurities on graphene by low-energy electron holography

TL;DR

This paper demonstrates the use of low-energy electron holography to visualize and reconstruct the potential distribution of individual charged impurities on graphene, a task challenging for traditional high-resolution microscopy.

Contribution

It introduces a novel application of low-energy electron holography combined with phase retrieval to image localized charge distributions on graphene.

Findings

Successfully visualized potential distribution of charged impurities

Reconstructed localized charge potentials using phase retrieval

Showed sensitivity of low-energy electrons to potential gradients

Abstract

While imaging individual atoms can routinely be achieved in high resolution transmission electron microscopy, visualizing the potential distribution of individually charged adsorbates leading to a phase shift of the probing electron wave is still a challenging task. Low-energy electrons (30 - 250 eV) are sensitive to localized potential gradients. We employed low-energy electron holography to acquire in-line holograms of individual charged impurities on free-standing graphene. By applying an iterative phase retrieval reconstruction routine we recover the potential distribution of the localized charged impurities present on free-standing graphene.