Defect-induced oxygen adsorption on graphene films

TL;DR

This study investigates how carbon vacancy defects in graphene influence oxygen adsorption, revealing that defect size determines whether oxygen adsorbs molecularly or dissociatively, impacting graphene's protective capabilities.

Contribution

It demonstrates the role of defect size in oxygen adsorption behavior on graphene, highlighting the importance of defect control for protective applications.

Findings

Oxygen does not attach to intact graphene.

Oxygen adsorbs at defect sites after annealing.

Large defects lead to dissociative chemisorption on Ru.

Abstract

Although defects on graphene can degrade electron transport and its ability for use as a protection layer, they can also be helpful to tailor the local properties or activate new sites for particular adsorbates. Here, carbon vacancy defects are formed in graphene films on Ru(0001) using low energy Ar$^+$ bombardment and the materials are then reacted at room temperature with oxygen (O$_2$). Helium low energy ion scattering shows that no oxygen attaches to the intact graphene layer. When isolated single carbon vacancy defects are present, oxygen adsorbs molecularly at the defect sites and intercalates beneath the graphene overlayer after post-annealing at 600 K. When the defects are large enough to consist of open areas of bare substrate, the oxygen dissociatively chemisorbs to the Ru. This work shows that the adsorption depends on the size of the surface vacancies, and that it is important to have defect-free graphene when using it as a protection layer.