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O: Fachverband Oberflächenphysik

O 17: Adsorption on Metal Surfaces

O 17.2: Vortrag

Montag, 7. März 2016, 15:15–15:30, H6

Is Cu₂N/Cu(100) a good insulator? An STM/STS study of a metal-organic monolayer — •Pascal R. Ewen^1,2, Cristian A. Strassert², Alexander A. Khajetoorians², and Daniel Wegner² — ¹Radboud Universtiteit, Nijmegen, The Netherlands — ²Westfälische Wilhelms-Universtität, Münster, Germany

The study of molecules by scanning tunneling microscopy (STM) and spectroscopy (STS) also includes probing molecule-substrate interactions, which can change physical properties from hybridization to charge transfer and even to drastic effects such as decomposition. A thin insulating film can significantly decouple the adsorbate leading to a behaviour comparable to the isolated molecule. But it turns out that the decreased interaction with the substrate often causes drawbacks in the sample preparation or scanning conditions due to lower sticking coefficients or higher mobilities even at low temperature. In that respect, Cu₂N layers have recently gained increasing interest.

We investigate Pt(II) complexes that are used as emitters in prototypical OLEDs. Previously, we have shown that Pt-based orbitals are strongly influenced even by a Au(111) surface, which is commonly considered to show weak adsorbate-substrate interactions. Therefore, we have chosen to investigate the decoupling capability of Cu₂N/Cu(100) for these complexes. We found that the molecules self-assemble into a well-ordered monolayer. We determined adsorption geometry by STM and carefully analysed the spatial and energy distribution of molecular orbitals via STS-based spectral mapping to evaluate the impact of the substrate on the molecule.