Graphene healing mechanisms: A theoretical investigation

TL;DR

This study uses atomistic simulations to explore how graphene heals from large holes under various conditions, revealing the roles of temperature, electron beam effects, and atomic rearrangements in the healing process.

Contribution

It provides a detailed atomistic understanding of graphene healing mechanisms under different experimental conditions, including the effects of temperature and electron beam influence.

Findings

High temperatures enable perfect graphene reconstruction with a carbon source.

Room temperature healing involves electron beam heat effects and formation of carbon chains.

Reconstruction includes formation of rings with 5-8 atoms and planar/non-planar structures.

Abstract

Large holes in graphene membranes were recently shown to heal, either at room temperature during a low energy STEM experiment, or by annealing at high temperatures. However, the details of the healing mechanism remain unclear. We carried out fully atomistic reactive molecular dynamics simulations in order to address these mechanisms under different experimental conditions. Our results show that, if a carbon atom source is present, high temperatures can provide enough energy for the carbon atoms to overcome the potential energy barrier and to produce perfect reconstruction of the graphene hexagonal structure. At room temperature, this perfect healing is only possible if the heat effects of the electron beam from STEM experiment are explicitly taken into account. The reconstruction process of a perfect or near perfect graphene structure involves the formation of linear carbon chains, as well as rings containing 5, 6, 7 and 8 atoms with planar (Stone-Wales) and non-planar (lump like) structures. These results shed light on the healing mechanism of graphene when subjected to different experimental conditions. Additionally, the methodology presented here can be useful for investigating the tailoring and manipulations of other nano-structures.