Intercalation and desorption of oxygen between graphene and Ru(0001) studied with helium ion scattering

TL;DR

This study investigates how oxygen intercalates between graphene and Ru(0001), using helium ion scattering to reveal that oxygen intercalates as molecules and desorbs at 800 K, affecting graphene integrity.

Contribution

It provides direct experimental evidence of molecular oxygen intercalation and desorption behavior between graphene and Ru(0001) using helium ion scattering.

Findings

Oxygen intercalates as molecules, not adsorbed on graphene.

Intercalated O2 desorbs at 800 K, lower than atomic oxygen.

Graphene etching occurs during oxygen desorption, depending on intercalated amount.

Abstract

Graphene is a fascinating 2D material that is being widely investigated for use in electronic devices due to its unique electronic and materials properties. Also, because of its high thermal stability and inertness, it is considered a promising candidate for use as a protection layer for metal substrates. Here, graphene films grown on Ru(0001) are held at 600 K while reacted with oxygen (O$_2$) and then investigated with helium low energy ion scattering (LEIS). LEIS spectra collected at different scattering angles confirm that oxygen does not adsorb to graphene, but instead intercalates between the graphene and the substrate. The intercalated O$_2$ desorbs when the sample is annealed to 800 K. It is shown that this is a much lower temperature than is needed to remove chemisorbed atomic oxygen from Ru, thus inferring that the intercalated oxygen is molecular. During the desorption process, some of the graphene is etched away via a chemical reaction with the oxygen, with the proportion desorbing as O$_2$ or reacting to etch the graphene being dependent on the amount of intercalated O$_2$.