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Nano Research 2016, 9(9): 2735-2746 https://doi.org/10.1007/s12274-016-1162-2
Research Article | Issue | Published: 18 July 2016

Effect of electron injection in copper-contacted graphene nanoribbons

Show Author's Information Konstantin A. Simonov1,2,3( ),  Nikolay A. Vinogradov2,3,  Alexander S. Vinogradov3,  Alexander V. Generalov2,3,  Gleb I. Svirskiy3,  Attilio A. Cafolla4,  Nils Mårtensson1,  Alexei B. Preobrajenski2( )
Department of Physics and AstronomyUppsala UniversityUppsala Box 51675120Sweden
MAX IV LaboratoryLund UniversityLund Box 11822100Sweden
V. A. Fock Institute of PhysicsSt. Petersburg State UniversitySt. Petersburg198504Russia
School of Physical SciencesDublin City UniversityDublin 9Ireland
Keywords:
scanning tunneling microscopy, graphene nanoribbons, bottom-up method, copper intercalation, charge injection, angle-resolved photoemission spectroscopy (ARPES)
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Simonov KA, Vinogradov NA, Vinogradov AS, et al. Effect of electron injection in copper-contacted graphene nanoribbons. Nano Research, 2016, 9(9): 2735-2746. https://doi.org/10.1007/s12274-016-1162-2
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Abstract Full text Electronic supplementary material About this article

For practical electronic device applications of graphene nanoribbons (GNRs), it is essential to have abrupt and well-defined contacts between the ribbon and the adjacent metal lead. By analogy with graphene, these contacts can induce electron or hole doping, which may significantly affect the I/V characteristics of the device. Cu is among the most popular metals of choice for contact materials. In this study, we investigate the effect of in situ intercalation of Cu on the electronic structure of atomically precise, spatially aligned armchair GNRs of width N = 7 (7-AGNRs) fabricated via a bottom-up method on the Au(788) surface. Scanning tunneling microscopy data reveal that the complete intercalation of about one monolayer of Cu under 7-AGNRs can be facilitated by gentle annealing of the sample at 80 ℃. Angle-resolved photoemission spectroscopy (ARPES) data clearly reflect the one-dimensional character of the 7-AGNR band dispersion before and after intercalation. Moreover, ARPES and core-level photoemission results show that intercalation of Cu leads to significant electron injection into the nanoribbons, which causes a pronounced downshift of the valence and conduction bands of the GNR with respect to the Fermi energy (ΔE ~ 0.5 eV). As demonstrated by ARPES and X-ray absorption spectroscopy measurements, the effect of Cu intercalation is restricted to n-doping only, without considerable modification of the band structure of the GNRs. Post-annealing of the 7-AGNRs/Cu/Au(788) system at 200 ℃ activates the diffusion of Cu into Au and the formation of a Cu-rich surface Au layer. Alloying of intercalated Cu leads to the recovery of the initial position of GNR-related bands with respect to the Fermi energy (EF), thus, proving the tunability of the induced n-doping.


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Electronic supplementary material
About this article

Effect of electron injection in copper-contacted graphene nanoribbons

Show Author's information Konstantin A. Simonov1,2,3( ), Nikolay A. Vinogradov2,3, Alexander S. Vinogradov3, Alexander V. Generalov2,3, Gleb I. Svirskiy3, Attilio A. Cafolla4, Nils Mårtensson1, Alexei B. Preobrajenski2( )
Department of Physics and AstronomyUppsala UniversityUppsala Box 51675120Sweden
MAX IV LaboratoryLund UniversityLund Box 11822100Sweden
V. A. Fock Institute of PhysicsSt. Petersburg State UniversitySt. Petersburg198504Russia
School of Physical SciencesDublin City UniversityDublin 9Ireland

Abstract

For practical electronic device applications of graphene nanoribbons (GNRs), it is essential to have abrupt and well-defined contacts between the ribbon and the adjacent metal lead. By analogy with graphene, these contacts can induce electron or hole doping, which may significantly affect the I/V characteristics of the device. Cu is among the most popular metals of choice for contact materials. In this study, we investigate the effect of in situ intercalation of Cu on the electronic structure of atomically precise, spatially aligned armchair GNRs of width N = 7 (7-AGNRs) fabricated via a bottom-up method on the Au(788) surface. Scanning tunneling microscopy data reveal that the complete intercalation of about one monolayer of Cu under 7-AGNRs can be facilitated by gentle annealing of the sample at 80 ℃. Angle-resolved photoemission spectroscopy (ARPES) data clearly reflect the one-dimensional character of the 7-AGNR band dispersion before and after intercalation. Moreover, ARPES and core-level photoemission results show that intercalation of Cu leads to significant electron injection into the nanoribbons, which causes a pronounced downshift of the valence and conduction bands of the GNR with respect to the Fermi energy (ΔE ~ 0.5 eV). As demonstrated by ARPES and X-ray absorption spectroscopy measurements, the effect of Cu intercalation is restricted to n-doping only, without considerable modification of the band structure of the GNRs. Post-annealing of the 7-AGNRs/Cu/Au(788) system at 200 ℃ activates the diffusion of Cu into Au and the formation of a Cu-rich surface Au layer. Alloying of intercalated Cu leads to the recovery of the initial position of GNR-related bands with respect to the Fermi energy (EF), thus, proving the tunability of the induced n-doping.

Keywords: scanning tunneling microscopy, graphene nanoribbons, bottom-up method, copper intercalation, charge injection, angle-resolved photoemission spectroscopy (ARPES)

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Publication history
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Acknowledgements

Publication history

Received: 07 April 2016
Revised: 24 May 2016
Accepted: 25 May 2016
Published: 18 July 2016
Issue date: September 2016

Copyright

© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2016

Acknowledgements

Acknowledgements

The authors are grateful for the financial support from the Swedish Research Council, the Swedish Energy Agency (STEM), the European Research Council under the European Union's Seventh Framework Programme (No. FP7/2007-2013)/ERC grant agreement n° [321319], Knut and Alice Wallenberg Foundation, the St. Petersburg State University (No. 11.38.638.2013), the Russian Foundation for Basic Research (No. 15-02-06369), the Science Foundation of Ireland through the Principal Investigator grant (No. SFI P.I.09/IN.1).

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