Probing Local Hydrogen Impurities in Quasi-Free-Standing Graphene

Autor(en)

Martha Scheffler, Danny Haberer, Luca Petaccia, Mani Farjam, Ronny Schlegel, Danny Baumann, Torben Hänke, Alexander Grüneis, Martin Knupfer, Christian Hess, Bernd Büchner

Abstrakt

We report high-resolution scanning tunneling microscopy and spectroscopy of hydrogenated, quasi-free-standing graphene. For this material, theory has predicted the appearance of a midgap state at the Fermi level, and first angle-resolved photo-emission spectroscopy (ARPES) studies have provided evidence for the existence of this state in the long-range electronic structure. However, the spatial extension of H defects, their preferential adsorption patterns on graphene, or local electronic structure are experimentally still largely unexplored. Here, we investigate the shapes and local electronic structure of H impurities that go with the aforementioned midgap state observed in ARPES. Our measurements of the local density of states at hydrogenated patches of graphene reveal a hydrogen impurity state near the Fermi level whose shape depends on the tip position with respect to the center of a patch. In the low H concentration regime, we further observe predominantly single hydrogenation sites as well as extended multiple C-H sites in parallel orientation to the lattice vectors, indicating an adsorption at the same graphene sublattice. This is corroborated by ARPES measurements showing the formation of a dispersionless hydrogen impurity state which is extended over the whole Brillouin zone.

Organisation(en)

Elektronische Materialeigenschaften

Externe Organisation(en)

Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Elettra Sincrotrone Trieste, Institute for Research in Fundamental Sciences (IPM)

Journal

ACS Nano

Band

6

Seiten

10590-10597

Anzahl der Seiten

8

ISSN

1936-0851

DOI

https://doi.org/10.1021/nn303485c

Publikationsdatum

2012

Peer-reviewed

Ja

ÖFOS 2012

103015 Kondensierte Materie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/3483aa93-006b-4140-ac01-e8011d86fd92