Sandwich molecular nanowires: on-surface synthesis, structure and magnetism

• Applicants: Dr. Nicolae Atodiresei; Professor Dr. Thomas Werner Michely; Professor Dr. Heiko Wende
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2017 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389895192

• Final Report Year: 2022

Final Report Abstract

In summary, within the project we successfully explored a new principle of on-surface synthesis for organometallic compounds and generalized it in terms of metals, ligands and suitable substrate. A surprising finding of the research with substantial impact is the possibility to tune reactions by the electron chemical potential. For characterization of the magnetic and electronic structure of the one-dimensional sandwich molecular wires we developed a new uniaxial templating substrate, namely graphene on Ir(110). It is likely that this uniaxial template will find widespread application for template adsorption of molecules. The organo-metallic compounds synthesized were more sensitive than anticipated which impaired the characterization of their magnetic and electronic structure. Nevertheless, a hitherto unknown dot compound consisting of dots formed by a rare earth atom sandwiched between cyclooctatetraene and Gr displays very large anisotropy making them interesting for spintronic applications. Inspired by these results we investigated the properties of rare earth alloy with Ir(111) and found a drastic change of the magnetic properties when Gr is adsorbed to the surface alloy. The strongly increased anisotropy can be traced back to the “sky hook” effect, namely the fact that Gr selectively pulls out rare earth atoms from the surface, which could be confirmed and reproduced by our multiplet approach. In terms of future investigations, a close collaboration with a synthetic chemist would be the best option to explore the full power of our new on-surface synthesis principle. While the sensitivity of the synthesized compounds, specifically those with metal oxidation state 2+, to radiation damage, makes spectroscopic research on these compounds cumbersome, the rare earth surface alloys in combination with Gr or other 2D layers are exciting materials with unique properties that deserve additional research.

Publications

• Europium Cyclooctatetraene Nanowire Carpets: A Low-Dimensional, Organometallic, and Ferromagnetic Insulator. The Journal of Physical Chemistry Letters 10, 5 (2019)
  F. Huttmann, N. Rothenbach, S. Kraus, K. Ollefs, L. M. Arrud, M. Bernien, D. Thonig, A. Delin, J. Franson, K. Kummer, N. B. Brooks, O. Eriksson, W. Kuch, T. Michely, and H. Wende
  
• On-surface synthesis of sandwich-molecular wires, Dissertation (Universität zu Köln, 2021)
  S. Kraus
  
• Selecting the Reaction Path in On-Surface Synthesis through the Electron Chemical Potential in Graphene. Journal of the American Chemical Society 144, 24, 11003–110092022 (2022)
  S. Kraus, A. Herman, F. Huttmann, C. Krämer, K. Amsharov, S. Tsukamoto, H. Wende, N. Atodiresei, and T. Michely
  
• Single-crystal graphene on Ir(110). Physical Review B 105, 16 (2022)
  S. Kraus, F. Huttmann, J. Fischer, T. Knispel, K. Bischof, A. Herman, M. Bianchi, R. M. Stan, A. J. Holt, V. Caciuc, S. Tsukamoto, H. Wende, P. Hofmann, N Atodiresei, and T. Michely
  
• Tailoring magnetic anisotropy by graphene-induced selective skyhook effect on 4f-metals. Nanoscale 14, 20 (2022)
  A. Herman, S. Kraus, S. Tsukamoto, L. Spieker, V. Caciuc, T. Lojewski, D. Günzing, J. Dreiser, B. Delley, K. Ollefs, T. Michely, N. Atodiresei and H. Wende
  
• Uniaxially Aligned 1D Sandwich-Molecular Wires: Electronic Structure and Magnetism. The Journal of Physical Chemistry C 126, 6 (2022)
  Kraus, A. Herman, F. Huttmann, M. Bianchi, R. M. Stan, A. J. Holt, S. Tsukamoto, N. Rothenbach, K. Ollefs, J. Dreiser, K. Bischof, H. Wende, P. Hofmann, N. Atodiresei, and T. Michely