Charged defects in graphene and the ionicity of hexagonal boron nitride in direct images

TL;DR

This paper demonstrates how aberration-corrected HRTEM combined with first-principles calculations can directly visualize charge distributions and electronic configurations in defects and materials like graphene and hexagonal boron nitride.

Contribution

It introduces a novel method to analyze charge states and electronic structures in 2D materials using direct imaging and theoretical calculations.

Findings

Nitrogen dopants in graphene can be detected and their charge states analyzed.

The ionicity of hexagonal boron nitride can be confirmed from direct images.

Adjustments to atomic potentials due to chemical bonding are observable in HRTEM images.

Abstract

We report on the detection and charge distribution analysis for nitrogen substitutional dopants in single layer graphene membranes by aberration-corrected high-resolution transmission electron microscopy (HRTEM). Further, we show that the ionicity of single-layer hexagonal boron nitride can be confirmed from direct images. For the first time, we demonstrate by a combination of HRTEM experiments and first-principles electronic structure calculations that adjustments to the atomic potentials due to chemical bonding can be discerned in HRTEM images. Our experiments open a way to discern electronic configurations in point defects or other non-periodic arrangements or nanoscale objects that can not be analyzed in an electron or x-ray diffraction experiment.