Complex evolution of the electronic structure from polycrystalline to monocrystalline graphene: generation of a new Dirac point

TL;DR

This study uses first principles calculations to explore how the electronic structure of polycrystalline graphene evolves with tilt grain boundaries, revealing a new Dirac point and complex energy behaviors as the system approaches monocrystalline graphene.

Contribution

It uncovers the complex evolution of electronic properties and the formation of a new Dirac point in polycrystalline graphene as a function of tilt angle, a novel insight into graphene's electronic behavior.

Findings

Generation of a new Dirac point at the Fermi level.

Non-monotonic behavior of grain-boundary formation energy.

Evolution of the Dirac cone and energy levels with tilt angle.

Abstract

First principles calculations, employed to address the properties of polycrystalline graphene, indicate that the electronic structure of tilt grain boundaries in this system displays a rather complex evolution towards graphene bulk, as the tilt angle decreases, with the generation of a new Dirac point at the Fermi level, and an anisotropic Dirac cone of low energy excitations. Moreover, the usual Dirac point at the {\bf K} point falls below the Fermi level, and rises towards it as the tilt angle decreases. Further, our calculations indicate that the grain-boundary formation energy behaves non-monotonically with the tilt angle, due to a change in the the spatial distribution and relative contributions of the bond-stretching and bond-bending deformations associated with the formation of the defect.