Patterning graphene with hydrogen clusters

The formation and thermal stability of the hydrogen structures on the graphene/Ir(111) interface were investigated by means of fast X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. The evolution of the C 1s and Ir 4f_7/2 core levels was monitored in situ during hydrogenation and dehydrogenation of graphene in order to follow the modality of H adsorption and desorption with H₂ recombination. DFT calculations have been used to investigate different arrangements of the H atoms and the corresponding C 1s binding energy shifts.
The comparison between experimental and theoretical results allowed revealing preferential adsorption of hydrogen on hcp and fcc regions of the moiré superstructure at low coverage, with the corresponding formation of graphane-like clusters. At higher coverage also hydrogen dimers form on the atop regions of the graphene/Ir(111) interface.
 

Furthermore, the higher thermal stability of the graphane-like clusters in the hpc and fcc regions opens the possibility to pattern the graphene layer with size-selected hydrogen structures by thermal annealing of a saturated layer. The ability to control the hydrogenated areas at the nanometer scale may have large implications for tuning the band gap in graphene as well as for tailoring the properties of graphene with large functional groups.

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