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Controlled thermodynamics for tunable electron doping of graphene on Ir(111)

Authors/others:Struzzi, C. (Elettra Sincrotrone Trieste) Praveen, C. S. (CNR, Consiglio Nazionale delle Ricerche (CNR), Ist Officina Mat IOM DEMOCRITOS) Scardamaglia, M. (University of Mons ) Verbitskiy, N. I. (Lomonosov Moscow State University (MSU)) Fedorov, A. V. (Universität zu Köln) Weinl, M. (Universität Augsburg) Schreck, M. (Universität Augsburg) Grüneis, Alexander (Universität zu Köln) Piccinin, S. (CNR, Consiglio Nazionale delle Ricerche (CNR), Ist Officina Mat IOM DEMOCRITOS) Fabris, S. (CNR, Consiglio Nazionale delle Ricerche (CNR), Ist Officina Mat IOM DEMOCRITOS) Petaccia, L. (Elettra Sincrotrone Trieste)
Abstract:The electronic properties and surface structures of K-doped graphene supported on Ir(111) are characterized as a function of temperature and coverage by combining low-energy electron diffraction, angle-resolved photoemission spectroscopy, and density functional theory (DFT) calculations. Deposition of K on graphene at room temperature (RT) yields a stable (root 3 x root 3) R30 degrees surface structure having an intrinsic electron doping that shifts the graphene Dirac point by E-D = 1.30 eV below the Fermi level. Keeping the graphene substrate at 80 K during deposition generates instead a (2 x 2) phase, which is stable until full monolayer coverage. Further deposition of K followed by RT annealing develops a double-layer K-doped graphene that effectively doubles the K coverage and the related charge transfer, as well as maximizing the doping level (E-D = 1.61 eV). The measured electron doping and the surface reconstructions are rationalized by DFT calculations. These indicate a large thermodynamic driving force for K intercalation below the graphene layer. The electron doping and Dirac point shifts calculated for the different structures are in agreement with the experimental measurements. In particular, the K-4s bands are shown to be sensitive to both the K intercalation and periodicity and are therefore suggested as a fingerprint for the location and ordering of the K dopants.
Number of pages:10
Date of publication:25.8.2016
Journal title:Physical Review B (Condensed Matter and Materials Physics)
Digital Object Identifier (DOI):http://dx.doi.org/10.1103/PhysRevB.94.085427
Publication Type:Article
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