Low energy graphene edge termination via small diameter nanotube formation

TL;DR

This paper shows that graphene edges can spontaneously curl into nanotubes, lowering energy and creating metallic conduction channels, with implications for graphene's electronic properties and edge detection.

Contribution

It introduces a novel edge reconstruction mechanism where graphene edges form nanotubes, with detailed analysis of formation energies, barriers, and electronic properties.

Findings

Graphene edges can curl into nanotubes, lowering formation energy.

Rolled edges act as metallic conduction channels.

High-resolution microscopy may not easily detect these rolled edges.

Abstract

We demonstrate that free graphene sheet edges can curl back on themselves,reconstructing as nanotubes. This results in lower formation energies than any other non-functionalised edge structure reported to date in the literature. We determine the critical tube size and formation barrier and compare with density functional simulations of other edge terminations including a new reconstructed Klein edge. Simulated high resolution electron microscopy images show why such rolled edges may be difficult to detect. Rolled zigzag edges serve as metallic conduction channels, separated from the neighbouring bulk graphene by a chain of insulating sp$^3$-carbon atoms, and introduce Van Hove singularities into the graphene density of states.