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Oxygen Switching of the Epitaxial Graphene-Metal Interaction

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Using photoemission spectroscopy techniques, we
show that oxygen intercalation is achieved on an extended layer of
epitaxial graphene on Ir(111), which results in the “lifting” of the
graphene layer and in its decoupling from the metal substrate. The
oxygen adsorption below graphene proceeds as on clean Ir(111),
giving only a slightly higher oxygen coverage. Upon lifting, the C 1s
signal shows a downshift in binding energy, due to the charge
transfer to graphene from the oxygen-covered metal surface.
Moreover, the characteristic spectral signatures of the graphenesubstrate interaction in the valence band are removed, and the spectrum of strongly
hole-doped, quasi free-standing graphene with a single Dirac cone around the K point is observed. The oxygen can be deintercalated by annealing, and this
process takes place at around T = 600 K, in a rather abrupt way. A small amount of carbon atoms is lost, implying that graphene has been etched. After
deintercalation graphene restores its interaction with the Ir(111) substrate. Additional intercalation/deintercalation cycles readily occur at lower oxygen
doses and temperatures, consistently with an increasingly defective lattice. Our findings demonstrate that oxygen intercalation is an efficient method for
fully decoupling an extended layer of graphene from a metal substrate, such as Ir(111). They pave the way for the fundamental research on graphene,
where extended, ordered layers of free-standing graphene are important and, due to the stability of the intercalated system in a wide temperature range,
also for the advancement of next-generation graphene-based electronics.
KEYWORDS: epitaxial graphene . Ir(111) . oxygen intercalation . doping
Original languageEnglish
JournalA C S Nano
Pages (from-to)9551–9558
Number of pages8
Publication statusPublished - 2012

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