Tailoring spin-interactions in graphene nanoribbons for ballistic fully spin-polarized devices

• Applicants: Professor Dr. Ulrich Starke; Professor Dr. Christoph Tegenkamp
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279056547

• Final Report Year: 2020

Final Report Abstract

The TAILSPIN aims to realize an “all-graphene” spin-valve device and is inspired by our discovery of ballistic and fully spin-polarized transport at room temperature for graphene nanoribbons (GNRs) grown on prestructured SiC(0001) surfaces. We obtained clear evidence that the origin of the observed unique properties is governed by the presence of robust edge states. The unique role of the electronic and magnetic properties of these edge states is the central research topic in this proposal, which in combination with electronic charge and spin transport studies in dedicated devices will reveal crucial information about the underlying mechanism for the ballistic and magnetic behavior. The major objective is to explore the unique possibilities of this system to realize spintronic devices where the entire spin valve architecture is made by a single GNR. This creates an entirely new platform for both fundamental as well as application driven research of quasi one-dimensional carbon based magnetism and spintronics. In detail, the TAILSPIN project covers the following aspects: (a) Optimization of the growth process for a large scale needs to be promoted for future applications; (b) Microscopic understanding of the ballistic and spin-polarized behavior by the anomalous electronic structure of the edge states by combining different electron spectroscopic and spin transport; (c) Functionalization of GNRs via selective atomistic manipulation, adsorption and intercalation under consideration of defects; (d) Finally, the engineering of prototype spin-valve devices, and exploring the transport properties as a function of the applied magnetic field, temperature, and functionalization of the GNR. The expertise of the TAILSPIN partners bridges the gap between atomic and mesoscopic scales and the complementary methods cover the fields of controlled growth, structure (STM, LEEM), electronic structure (STS, ARPES, PEEM) and transport (4-tip STM/SEM, cryogenic spin transport). The targeted sharing into different tasks addresses aspects regarding the precise engineering of nanoribbons with tailored edge states as well as further functionalization by local manipulation, e.g. adsorption and intercalation. This finally allows us to derive a detailed model about the relevant microscopic interactions on various length scales giving rise to the anomalous electronic structure of the edge states. Within the first year of the TAILSPIN project we successfully optimized the growth parameters such that large ensembles of zig-zag or arm-chair ribbons can be fabricated on SiC-mesa structures. Moreover, by applying a twofold heating procedure, the parasitic effect of the SiC facet instability is suppressed, so 40nm wide ribbons are obtained. On these ribbons, we performed spectroscopic measurements, which revealed both the presence of bulk and edge states in these structures. Latest transport measurements support the ballistic character: in particular, we got a deeper insight into the invasiveness of our contacts and succeeded to measure also 4e²/h channels for probe distances around 60nm. The asymmetric bonding of the edges of the ribbon seems to be very important in order to explain the robust edge state as well as the spin- and pseudospin degenerated bulk states. In addition, high resolution STM/STS as well as TEM provide now microscopic details, which are taken into account for the ongoing theoretical modeling.

Publications

• Vacancy formation on C60/Pt (111): unraveling the complex atomistic mechanism. Nanotechnology, 25, 385602-1/13 (2014)
  Pinardi, A. L., Biddau, G., Ruit, van de, K., Otero-Irurueta, G., Gardonio, S., Lizzit, S., ... Martin-Gago, J. A.
  
• Ballistic bipolar junctions in chemically gated graphene ribbons. Sci. Rep. 5, 9955 (2015)
  J. Baringhaus, A. Stöhr, S. Forti, U. Starke, C. Tegenkamp
  
• Evidence for superconductivity in Li-decorated monolayer graphene, Proc. Nat. Acad. Soc. 112, 11795 (2015)
  B.M. Ludbrook, G.Levy, P. Nigge, M. Zonno, M. Schneider, D.J. Dvorak, C.N. Veenstra, S. Zhdanovich, D. Wong, P. Dosanjh, C. Straßer, A. Stöhr, S. Forti, C.R. Ast, U. Starke, and A. Damascelli
  
• Growth and characterization of sidewall graphene nanoribbons. Appl. Phys. Lett. 106, 043109 (2015)
  J. Baringhaus, J. Aprojanz, J.S. Wiegand, D. Laube, M. Halbauer, J. Hübner, M. Oestreich, C. Tegenkamp
  
• Electron Interference in Ballistic Graphene Nanoconstrictions. Phys. Rev. Lett. 116, 186602 (2016)
  J. Baringhaus, M. Settnes, J. Aprojanz, S.R. Power, A.-P. Jauho, C. Tegenkamp
  
• Enhanced sensitivity of epitaxial graphene to NO2 by water coadsorption, Journal of Physical Chemistry C, 120(34), 19107 -19112 (2016)
  Ridene, M., Iezhokin, I., Offermans, P., & Flipse, C. F. J.
  
• Graphene Ribbon Growth on Structured Silicon Carbide. Annalen der Physics, 529, 1700052 (2017)
  A. Stöhr, J. Baringhaus, J. Aprojanz, S. Link, C. Tegenkamp, Y. Niu, A.A. Zakharov, C. Chen, J. Avila, M.C. Asensio, U. Starke
  
• Porphyrin molecules boost the sensitivity of epitaxial graphene for NH3 detection, Journal of Physics : Condensed Matter, 29(6), (2017)
  Iezhokin, I., den Boer, D., Offermans, P., Ridene, M., Elemans, J. A. A. W., Adriaans, G. P., & Flipse, C. F. J.
  
• 1D ballistic transport channel probed by invasive and noninvasive contacts. Appl Phys Lett, 113, 191602 (2018)
  J. Aprojanz, I. Miccoli, J. Baringhaus, C. Tegenkamp
  
• Ballistic tracks in graphene nanoribbons. Nature Communications, 9, 4426 (2018)
  J. Aprojanz, S.R. Power, P. Bampoulis, S. Roche, A.-P. Jauho, H.J.W. Zandvliet, A.A. Zakharov, C. Tegenkamp
  
• Electronic transport in graphene nanoribbons. Graphene Nanoribbons; Luis Brey, Pierre Seneor, Antonio Tejeda; IOP Publishing; Online ISBN: 978-0-7503-1701-6, Print ISBN: 978-0-7503-1699-6 (2019)
  C. Tegenkamp, J. Aprojanz, J. Baringhaus
  
• Epitaxial graphene on 6H-SiC(0001): Defects in SiC investigated by STEM. Phys. Rev. Materials, 3, 094004 (2019)
  M. Gruschwitz, H. Schletter, S. Schulze, I. Alexandrou, C. Tegenkamp
  
• Introducing strong correlation effects into graphene by gadolinium intercalation, Phys. Rev. B 100, 121407(R) (2019)
  S. Link, S. Forti, A. Stöhr, K. Küster, M. Rösner, D. Hirschmeier, C. Chen, J. Avila, M. C. Asensio,A. A. Zakharov, T. O. Wehling, A. I. Lichtenstein, M. I. Katsnelson, U. Starke
  
• Nanoscale Imaging of Electric Pathways in Epitaxial Graphene Nanoribbons, Nano Research 12, 1697 (2019)
  J. Aprojanz, P. Bampoulis, A.A. Zakharov, H.J.W. Zandvliet, C. Tegenkamp
  
• Origin of room-temperature ferromagnetism in hydrogenated epitaxial graphene on silicon carbide. Nanomaterials, 9(2) (2019)
  Ridene, M., Najafi, A., & Flipse, K.
  
• Semiconductor to metal transition in two-dimensional gold and its van der Waals heterostack with graphene
  S. Forti, S. Link, A. Stöhr, Y.R. Niu, A.A. Zakharov, C. Coletti, and U. Starke
  
• Tuning the doping level of graphene in the vicinity of the Van Hove singularity via ytterbium intercalation. Phys. Rev. B 100, 035445 (2019)
  P. Rosenzweig, H. Karakachian, S. Link, K. Küster, and U. Starke
  
• Wafer Scale Growth and Characterization of Edge Specific Graphene Nanoribbons for Nanoelectronics, ACS Appl Nano Mater, 2, 156 (2019)
  A.A. Zakharov, N.A. Vinogradov, J. Aprojanz, T.T.N. Nguyen, C. Tegenkamp, C. Struzzi, T. Yakimov, R. Yakimova, V. Jokubavicius
  
• Substrate induced nanoscale resistance variation in epitaxial graphene. Nature Communications, Vol. 11, 555 (2020)
  A. Sinterhauf, G.A. Traeger, D. Momeni Pakdehi, P. Schädlich, P. Willke, F. Speck, T. Seyller, C. Tegenkamp, K. Pierz, H.W. Schumacher, M. Wenderoth