Hydrogenated graphene on Ir(111): A high-resolution electron energy loss spectroscopy study of the vibrational spectrum

Line Kyhl (1) , Richard Balog (2) , Thierry Angot (3) , Liv Hornekaer (1, 2) , Régis Bisson (3)

1 iNANO - Interdisciplinary Nanoscience Center
2 Department of Physics and Astronomy [Aarhus]
3 PIIM - Physique des interactions ioniques et moléculaires

Hydrogen atom adsorption on high-quality graphene on Ir(111) [gr/Ir(111)] is investigated using high-resolution electron energy loss spectroscopy. The evolution of the vibrational spectrum, up to 400 meV, of gr/Ir(111) upon increasing hydrogen atom exposures is measured. The two dominant binding configurations of atomic hydrogen are identified as (1) graphanelike hydrogen clusters on the parts of the graphene more strongly interacting with the Ir(111) surface and (2) dimers bound more weakly to the freestanding parts of the graphene. The graphanelike surface structures lead to increased corrugation of the graphene sheet, yielding graphane-related phonon components. Additionally, a recent theoretical prediction of the existence of a bending character for a LO/TO graphane chair phonon mode is experimentally verified. No clear evidence was found for hydrogen bound on both sides of a high-quality graphene sheet and phonon features strongly suggest interactions between graphanelike hydrogen clusters and Ir atoms in the substrate.

Domaines: Chimie-Physique [physics.chem-ph]; Matière Condensée [cond-mat]; Physique [physics]

Line Kyhl, Richard Balog, Thierry Angot, Liv Hornekaer, Régis Bisson. Hydrogenated graphene on Ir(111): A high-resolution electron energy loss spectroscopy study of the vibrational spectrum. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2016, 93, pp.115403. ⟨10.1103/PhysRevB.93.115403⟩. ⟨hal-01284577⟩