Intercalating cobalt between graphene and iridium (111): a spatially-dependent kinetics from the edges

TL;DR

This study uses real-time microscopy to investigate how cobalt intercalates between graphene and iridium, revealing edge-dependent energy barriers and the surfactant role of graphene in stabilizing cobalt layers.

Contribution

It provides the first real-time imaging of cobalt intercalation at graphene edges and quantifies local variations in energy barriers influenced by graphene orientation and edge termination.

Findings

Edges act as energy barriers to cobalt intercalation.

Graphene's presence lowers cobalt's energy on iridium, acting as a surfactant.

Local variations in barrier height depend on graphene orientation and edge termination.

Abstract

Using low-energy electron microscopy, we image in real time the intercalation of a cobalt monolayer between graphene and the (111) surface of iridium. Our measurements reveal that the edges of a graphene flake represent an energy barrier to intercalation. Based on a simple description of the growth kinetics, we estimate this energy barrier and find small, but substantial, local variations. These local variations suggest a possible influence of the graphene orientation with respect to its substrate and of the graphene edge termination on the energy value of the barrier height. Besides, our measurements show that intercalated cobalt is energetically more favorable than cobalt on bare iridium, indicating a surfactant role of graphene.