Time-resolved two-photon photoemission of unoccupied electronic states of periodically rippled graphene on Ru(0001)

The unoccupied electronic states of epitaxially grown graphene on Ru(0001) have been explored by time- and angle-resolved two-photon photoemission. We identify a Ru derived resonance and a Ru/graphene interface state at 0.91 and 2.58 eV above the Fermi level, as well as three image-potential derived...

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Bibliographic Details
Published in:Physical review letters 2012-01, Vol.108 (5), p.056801-056801, Article 056801
Main Authors: Armbrust, N, Güdde, J, Jakob, P, Höfer, U
Format: Article
Language:English
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Summary:The unoccupied electronic states of epitaxially grown graphene on Ru(0001) have been explored by time- and angle-resolved two-photon photoemission. We identify a Ru derived resonance and a Ru/graphene interface state at 0.91 and 2.58 eV above the Fermi level, as well as three image-potential derived states close to the vacuum level. The most strongly bound, short-lived, and least dispersing image-potential state is suggested to have some quantum-well character with a large amplitude below the graphene hills. The two other image-potential states are attributed to a series of slightly decoupled states. Their lifetimes and dispersions are indicative of electrons moving almost freely above the valley areas of the moiré superstructure of graphene.
ISSN:0031-9007
1079-7114
DOI:10.1103/physrevlett.108.056801