Understanding the catalyst-free transformation of amorphous carbon into graphene by current-induced annealing

TL;DR

This study reveals how amorphous carbon transforms into graphene through current-induced annealing without catalysts, using experiments and simulations to uncover the underlying mechanisms and potential for device engineering.

Contribution

It demonstrates the catalyst-free growth process of graphene from amorphous carbon and introduces the novel observation of graphene growth from hole borders.

Findings

Small a-C clusters crystallize into graphene patches.

Graphene can grow from hole borders in the presence of a-C.

The process is facilitated by high temperatures and van der Waals interactions.

Abstract

We shed light on the catalyst-free growth of graphene from amorphous carbon (a-C) by current-induced annealing by witnessing the mechanism both with in-situ transmission electron microscopy and with molecular dynamics simulations. Both in experiment and in simulation, we observe that small a-C clusters on top of a graphene substrate rearrange and crystallize into graphene patches. The process is aided by the high temperatures involved and by the van der Waals interactions with the substrate. Furthermore, in the presence of a-C, graphene can grow from the borders of holes and form a seamless graphene sheet, a novel finding that has not been reported before and that is reproduced by the simulations as well. These findings open up new avenues for bottom-up engineering of graphene-based devices.