[Paper Review] Electronic structure of Graphene/Co interfaces

D. Pacilè, Simone Lisi+13 more|arXiv (Cornell University)|Feb 23, 2026

Graphene research and applications0 citations

TL;DR

The study investigates graphene on Co intercalated on Ir(111), revealing phase-dependent C 1s and graphene valence-band features and indicating inequivalent carbon adsorption sites even in a commensurate phase.

ABSTRACT

Photoemission, from core levels and valence band, and low-energy electron diffraction (LEED) have been employed to investigate the electronic and structural properties of novel graphene-ferromagnetic (G-FM) systems,obtained by intercalation of one mono-layer (1ML) and several layers (4ML) of Co on G grown on Ir(111). Upon intercalation of 1ML of Co, the Co lattice is resized to match the Ir-Ir lattice parameter, resulting in a mismatched G/Co/Ir(111) system. The intercalation of further Co layers leads to a relaxation of the Co lattice and a progressive formation of a commensurate G layer lying on top. We show the C 1s line shape and the band structure of G in the two artificial phases, mismatched and commensurate G/Co, through a comparison with the electronic structure of G grown directly on a Co thick film. Our results show that while the G valence band mainly reflects the hybridization with the d states of Co, regardless of the structural phase, the C 1s line shape is very sensitive to the rumpling of the G layer and the coordination of carbon atoms with the underlying Co. Even in the commensurate (1x1) G/Co phase, where graphene is in register with the Co film, from the angular dependence of the C 1s core level we infer the presence of a double component, due to in-equivalent adsorption sites of carbon sub-lattices.

Motivation & Objective

• Understand how Co intercalation modifies the electronic structure of graphene on Ir(111).
• Characterize structural phases created by Co intercalation (mismatched vs commensurate G/Co).
• Learn how core-level C 1s signals relate to graphene rumpling and carbon coordination with Co.
• Compare electronic structure of G on intercalated Co with G on thick Co films.

Proposed method

• Photoemission from core levels (C 1s) and valence band to probe electronic structure.
• Low-energy electron diffraction (LEED) to assess surface structure and phase relations.
• Intercalation of 1 monolayer (1ML) and several layers (4ML) of Co on graphene grown on Ir(111).
• Comparative analysis with graphene directly on thick Co films to interpret hybridization effects.

Experimental results

Research questions

• RQ1 How does Co intercalation alter the electronic structure of graphene on Ir(111)?
• RQ2 What are the structural characteristics of the mismatched versus commensurate G/Co phases?
• RQ3 How does the C 1s core level reflect graphene rumpling and carbon-Co coordination across phases?
• RQ4 Does the commensurate G/Co phase exhibit inequivalent adsorption sites for carbon sublattices?

Key findings

• Graphene valence band mainly reflects hybridization with Co d states, independent of the structural phase.
• C 1s line shape is highly sensitive to graphene rumpling and carbon-Co coordination.
• In the commensurate (1x1) G/Co phase, angular dependence of the C 1s core level shows a double component due to inequivalent adsorption sites of carbon sub-lattices.
• Intercalation drives the Co lattice to match Ir(111) parameters at 1ML, with further Co layers relaxing and enabling a commensurate G layer atop Co.
• The system transitions from a mismatched G/Co/Ir(111) arrangement toward a more uniform graphene-Co interaction as Co thickness increases.