Organic Heterolayer Systems: Structure and Vibrational Excitations

Summary

This project focuses on a detailed microscopic understanding of buried interfaces between organic thin films and metal substrates (via a molecular contact layer), as well as at the boundary of organic heterolayer systems. Thereby, infrared absorption spectroscopy (IRAS) will be used to investigate specific vibrational excitations at the organic/organic and organic/inorganic boundaries, for example, interfacial dynamical charge transfer associated with vibrational excitations. A major effort will be devoted to the in-situ preparation and characterization of customized layers. We will look into the structure and thermal stability of the interfaces with bare and functionalized metal surfaces and analyze related processes. Specifically, interfaces of organic heterolayer systems will be examined in terms of thin film inner structure, interdiffusion of the layered compounds, covalent bond formation and orientation effects at the interface.
On the basis of our excellent analytical characterization methods and control of growth conditions, sophisticated recipes to grow layered structures far from equilibrium will be developed. These in particular comprise increasingly more complex architectures as well as δ-layers embedded within homogeneous organic thin films. A major challenge of IRAS is to identify and characterize vibrational modes associated with the discontinuity at the interface, i.e. (i) modified bulk modes and (ii) genuine interface modes associated with species (atoms, molecules) exclusively located at the interface, or, specific binding configurations thereof. In this respect one of our aims is to identify chemical reactions at the interface by means of detection of specific low frequency vibrational modes.

Project-related Publications

1. S. Thussing, P. Jakob
   Thermal Stability and Interlayer Exchange Processes in Heterolayers of CuPc and PTCDA on Ag(111)
   J. Phys. Chem. C 121, 13680 (2017).
2. S. Thussing, L. Fernández, P. Jakob
   Thermal stability and interlayer exchange processes in heterolayers of TiOPc and PTCDA on Ag(111)
   J. Phys.: Condens. Matter 31, 134002 (2019) – Special Issue on Internal Interfaces.
3. S. Thussing, S. Flade, K. Eimre, C.A. Pignedoli, R. Fasel, P. Jakob
   Reaction Pathway toward Seven-Atom-Wide Armchair Graphene Nanoribbon Formation and Identification of Intermediate species on Au(111)
   J. Phys. Chem. C 124, 16009 (2020).
4. P. Jakob, S. Thussing
   Vibrational Frequency used as Internal Clock Reference to access Molecule – Metal Charge Transfer Times
   Phys. Rev. Lett. 126, 116801 (2021).