Implantation and atomic scale investigation of self-interstitials in graphene

TL;DR

This study reports the first atomic-scale imaging of self-interstitials in graphene, revealing their structures, aggregation behavior, and potential for defect engineering in two-dimensional materials.

Contribution

It provides the first experimental visualization of self-interstitials in graphene and explores their aggregation and energetic stability, advancing defect engineering in 2D materials.

Findings

Identified all predicted self-interstitial dimer structures in graphene.

Observed aggregation of interstitials into larger structures and dislocation dipoles.

Predicted strong local curvature and energetic favorability of aggregated defects.

Abstract

Crystallographic defects play a key role in determining the properties of crystalline materials. The new class of two-dimensional materials, foremost graphene, have enabled atomically resolved studies of defects, such as vacancies, grain boundaries, dislocations, and foreign atom substitutions. However, atomic resolution imaging of implanted self-interstitials has so far not been reported in any three- but also not in any two-dimensional material. Here, we deposit extra carbon into single-layer graphene at soft landing energies of ~1 eV using a standard carbon coater. We identify all the self-interstitial dimer structures theoretically predicted earlier, employing 80 kV aberration-corrected high-resolution transmission electron microscopy. We demonstrate accumulation of the interstitials into larger aggregates and dislocation dipoles, which we predict to have strong local curvature by atomistic modeling, and to be energetically favourable configurations as compared to isolated interstitial dimers. Our results contribute to the basic knowledge on crystallographic defects, and lay out a pathway into engineering the properties of graphene by pushing the crystal into a state of metastable supersaturation.