Electronic structure of Graphene/Co interfaces

TL;DR

This study investigates the electronic and structural properties of graphene interfaced with cobalt layers on Ir(111), revealing how Co intercalation affects lattice matching, hybridization, and core-level features in these novel G/Co systems.

Contribution

It provides detailed insights into the structural relaxation, lattice matching, and electronic hybridization in graphene/Co interfaces, highlighting the sensitivity of core-level spectra to local atomic arrangements.

Findings

Co intercalation causes lattice resizing and relaxation.

Graphene's valence band reflects hybridization with Co d states.

C 1s core level shows sensitivity to graphene's rumpling and adsorption sites.

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.