Beilstein Journal of Nanotechnology (Oct 2020)

Controlling the electronic and physical coupling on dielectric thin films

  • Philipp Hurdax,
  • Michael Hollerer,
  • Larissa Egger,
  • Georg Koller,
  • Xiaosheng Yang,
  • Anja Haags,
  • Serguei Soubatch,
  • Frank Stefan Tautz,
  • Mathias Richter,
  • Alexander Gottwald,
  • Peter Puschnig,
  • Martin Sterrer,
  • Michael G. Ramsey

DOI
https://doi.org/10.3762/bjnano.11.132
Journal volume & issue
Vol. 11, no. 1
pp. 1492 – 1503

Abstract

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Ultrathin dielectric/insulating films on metals are often used as decoupling layers to allow for the study of the electronic properties of adsorbed molecules without electronic interference from the underlying metal substrate. However, the presence of such decoupling layers may effectively change the electron donating properties of the substrate, for example, by lowering its work function and thus enhancing the charging of the molecular adsorbate layer through electron tunneling. Here, an experimental study of the charging of para-sexiphenyl (6P) on ultrathin MgO(100) films supported on Ag(100) is reported. By deliberately changing the work function of the MgO(100)/Ag(100) system, it is shown that the charge transfer (electronic coupling) into the 6P molecules can be controlled, and 6P monolayers with uncharged molecules (Schottky–Mott regime) and charged and uncharged molecules (Fermi level pinning regime) can be obtained. Furthermore, it was found that charge transfer and temperature strongly influence the orientation, conformation, and wetting behavior (physical coupling) of the 6P layers on the MgO(100) thin films.

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