First-Principles Study of the Role of O₂ and H₂O in the Decoupling of Graphene on Cu(111)

Abstract

The structural and electronic properties of graphene coated on a Cu(111) surface can be strongly influenced by the arrangement of adsorbates at the graphene edges. Oxygen and water intercalation at the graphene edges could lead to oxidation and hydrolysis at the graphene/Cu(111) interface, eventually causing decoupling of graphene from the Cu substrate. However, the reaction pathways for oxygen or water (or both) intercalation at the graphene edges are not well understood at the molecular level. Using ab initio density functional theory calculations, we observed a strong hybridization of π orbitals at a zigzag edge of a graphene nanoribbon (GNR) on a bare Cu(111) surface, whereas such hybridization was absent for the corresponding armchair edge under otherwise identical conditions. These results indicate that the edge type influences the oxidation chemistry beneath the GNR. Moreover, we demonstrate that the presence of oxygen species, as well as GNR, facilitates the propagation of H2O. The following decoupling mechanisms are discussed: (i) GNRs with armchair edge configurations on Cu(111) can be decoupled via a sequential reaction that involves O2 dissociation followed by H2O intercalation, whereas (ii) GNRs with zigzag edge configurations on Cu(111) can be decoupled by oxygen intercalation.

Effect of hydrogen passivation on the decoupling of graphene on SiC(0001) substrate: First-principles calculations

“…6 . In the final state, the right side of graphene is totally decoupled with SiC surface, which is similar to the results of previous study 36 . It is found that the energy barrier is very small (~0.06 eV) and the total energy of final state is 0.85 eV lower than the initial state, thus this process would happen very easily in experiments.…”

Intercalation, decomposition, entrapment – a new route to graphene nanobubbles

“…The Please do not adjust margins Please do not adjust margins second hypothesis is based upon chemical reactivity -water is a comparatively reactive molecule and molecular nitrogen is highly inert. H2O is known to dissociate at edge sites 46 , with reports that the graphene edge sites may in fact reduce the activation energy for H2O dissociation, compared to bare Cu 47 . It is possible that this decomposition is followed by hydroxyl diffusion across the surface, providing a route for H2O to escape.…”

Controlling Fundamental Fluctuations for Reproducible Growth of Large Single-Crystal Graphene

“…On the other hand, the existence of oxidants plays important roles in modulating the graphene growth. First, H 2 O and O 2 molecules adsorb onto the Cu surface, leading to the cleavage of O–O and O–H bonds to decompose into O species (O and OH radicals) at high growth temperature via coupled reactions: , We consider O and OH radicals as O-containing species because graphene growth is highly sensitive to them and the coupled reactions are more energetically favorable. − Disassociated O species on the Cu surface essentially have two possibilities of existence where they either diffuse on the Cu surface or dwell at energetically favorable sites via the formation of stable chemical bonds with the surface Cu atoms. On average, the former is responsible for etching C from the graphene lattice by random collision, and the latter is associated with the promoted nucleation of graphene.…”

“…On the other hand, the existence of oxidants plays important roles in modulating the graphene growth. First, H 2 O and O 2 molecules adsorb onto the Cu surface, leading to the cleavage of O−O and O−H bonds to decompose into O species (O and OH radicals) at high growth temperature via coupled reactions:22,23…”