Electronic band dispersion of graphene nanoribbons via Fourier-transformed scanning tunneling spectroscopy

Hajo Söde, Leopold Talirz, Oliver Gröning, Carlo Antonio Pignedoli, Reinhard Berger, Xinliang Feng, Klaus Müllen, Roman Fasel, and Pascal Ruffieux
Phys. Rev. B 91, 045429 – Published 23 January 2015
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Abstract

The electronic structure of atomically precise armchair graphene nanoribbons of width N=7 (7-AGNRs) are investigated by scanning tunneling spectroscopy (STS) on Au(111). We record the standing waves in the local density of states of finite ribbons as a function of sample bias and extract the dispersion relation of frontier electronic states by Fourier transformation. The wave-vector-dependent contributions from these states agree with density functional theory calculations, thus enabling the unambiguous assignment of the states to the valence band, the conduction band, and the next empty band with effective masses of 0.41±0.08me,0.40±0.18me, and 0.20±0.03me, respectively. By comparing the extracted dispersion relation for the conduction band to corresponding height-dependent tunneling spectra, we find that the conduction band edge can be resolved only at small tip-sample separations and has not been observed before. As a result, we report a band gap of 2.37±0.06 eV for 7-AGNRs adsorbed on Au(111).

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  • Received 11 July 2014

DOI:https://doi.org/10.1103/PhysRevB.91.045429

©2015 American Physical Society

Authors & Affiliations

Hajo Söde1, Leopold Talirz1, Oliver Gröning1, Carlo Antonio Pignedoli1,2, Reinhard Berger3, Xinliang Feng3, Klaus Müllen3, Roman Fasel1,4, and Pascal Ruffieux1,*

  • 1Empa, Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
  • 2NCCR MARVEL, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland
  • 3Max Planck Institute for Polymer Research, 55124 Mainz, Germany
  • 4Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

  • *pascal.ruffieux@empa.ch

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Vol. 91, Iss. 4 — 15 January 2015

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