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O: Fachverband Oberflächenphysik

O 46: Poster Organic Molecules on Inorganic Substrates: Electronic, Optical and Other Properties

O 46.9: Poster

Tuesday, March 18, 2025, 18:00–20:00, P2

Fluorescence spectroscopy of linear trans-quinacridone (QA) on KCl/Ag(100): The influence of KCl layer thickness — •Morris E. L. Mühlpointner and Moritz Sokolowski — Clausius-Institut für Physikalische und Theoretische Chemie der Universität Bonn, Germany

The organic dye-molecule linear QA has attracted interest as a fluorescent probe molecule in STM luminescence (STM-LE) experiments [1]. We have performed fluorescence spectroscopy of multilayers on the bare Ag(100) surface and highly diluted layers of QA on an epitaxially grown thin KCl film on Ag(100) under UHV.

We find spectra that are reminiscent of solid state spectra for multilayers of QA on Ag(100). In addition, we see blue-shifted spectra for highly dilute QA layers (0.0005 ML – 0.1 ML) with a multitude of spectral features. We find that the stability of these spectral features under laser illumination varies depending on the thickness of the underlying KCl layer. Spectra are stable at 13 K for QA on 3-4 layers of KCl. However, on 6-8 layers of KCl, a spectral red-shift and a loss of FL-intensity is induced upon laser illumination at 13 K. We attribute these findings to a diffusion barrier of QA on KCl films that is dependent on the KCl-film thicknesses because the long-range interactions with the Ag(100) substrate are relevant [2].

[1] Phys. Rev. Lett. 2023, 130 (12), 126202.

[2] J. Phys. Chem. C 2023, 127 (49), 23814-23826.

This work was supported by the DFG through the research training group 2591.

Keywords: Organic Molecules; FL-spectroscopy; KCl(100); Ag(100); Quinacridone