Electronic states of disordered grain boundaries in graphene prepared by chemical vapor deposition

TL;DR

This study investigates the electronic states at disordered grain boundaries in CVD-grown graphene, revealing localized low-energy states and the importance of disorder, modeled by vacancies, in reproducing experimental observations.

Contribution

The paper introduces an extended ab initio model incorporating disorder via vacancies to accurately simulate grain boundary electronic states in graphene.

Findings

Localized states near the Dirac point dominate the local density of states.

Disorder in the form of vacancies is essential to match experimental data.

Grain boundaries contain significant two-coordinated carbon atoms.

Abstract

Perturbations of the two dimensional carbon lattice of graphene, such as grain boundaries, have significant influence on the charge transport and mechanical properties of this material. Scanning tunneling microscopy measurements presented here show that localized states near the Dirac point dominate the local density of states of grain boundaries in graphene grown by chemical vapor deposition. Such low energy states are not reproduced by theoretical models which treat the grain boundaries as periodic dislocation-cores composed of pentagonal-heptagonal carbon rings. Using ab initio calculations, we have extended this model to include disorder, by introducing vacancies into a grain boundary consisting of periodic dislocation-cores. Within the framework of this model we were able to reproduce the measured density of states features. We present evidence that grain boundaries in graphene grown on copper incorporate a significant amount of disorder in the form of two-coordinated carbon atoms.