Recent research highlights
Selected research highlights. Research effords were mainly devoted to interface properties of small pi-conjugated molecules.
Research Highlight 2022 of the Synchrotron SOLEIL
July 2023: Our recent research on self organization properties of "Low band gap polymers" is online (SUSTAINABLE ENERGY, page 90)!
https://www.synchrotron-soleil.fr/highlights/2022/#page=90
The preferred molecular orientation of the studied "Low band gap" polymers depends strongly on the position and kind (alkyl or alkoxy) of the side chain at the thienylene spacers. The homogeneous molecular orientation within the 50 nm thick films enables the comparison of different methods for the determination of the molecular orientation with different surface sensitivity: X-ray absorption (XAS) in fluoreszence and electron yield mode as well as Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS). All methods deliver comparable and consistent information about the orientation of polymers in thin films. We suppose that these results promote comprehensive studies of the interplay between the chemical structure of polymers and self-organization properties in thin films, even with standard methods available in the home-lab, such as PM-IRRAS.
Influence of the Side Chain Structure on the Electronic Structure and Self-Organization Properties of Low Band Gap Polymers, Sven Bölke, David Batchelor, Andreas Früh, Benedikt Lassalle-Kaiser, Tina Keller, Florian Trilling, Michael Forster, Ullrich Scherf, Thomas Chassé, Heiko Peisert, ACS Appl. Energy Mater. 5 (2022) 15290–15301.
Visualization of the Borazine Core of B3N3-Doped Nanographene by STM
Electronic interface properties and the initial growth of hexa-peri-hexabenzocoronene with a borazine core (BN-HBC) on Au(111) have been studied by using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). A weak, but non-negligible, interaction between BN-HBC and Au(111) was found at the interface. Both hexa-peri-hexabenzocoronene (HBC) and BN-HBC molecules form well-defined monolayers. The different contrast in STM images of HBC and BN-HBC at different tunneling voltages with submolecular resolution can be ascribed to differences in the local density of states (LDOS). At positive and negative tunneling voltages, STM images reproduce the distribution of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) as determined by density functional theory (DFT) calculations very well.
Visualization of the Borazine Core of B3N3-Doped Nanographene by STM, Axel Belser, Katharina Greulich, Peter Grüninger, Holger Bettinger, Heiko Peisert, Thomas Chassé, ACS Appl. Mater. Interfaces 12 (2020) 19218−19225.
Charge Transfer from Organic Molecules to Molybdenum Disulfide: Influence of the Fluorination of Iron Phthalocyanine
Layered transition metal dichalcogenides (TMDCs), such as molybdenum disulfide (MoS2), are currently in the focus of interest due to their novel electronic properties. The adsorption of molecules is a promising way to tune the electronic structure of TMDCs. We study interface properties between MoS2 and differently fluorinated iron phthalocyanines (FePcFx, x = 0, 4, 16) using X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), angle-resolved photoelectron spectroscopy (ARPES), and X-ray absorption spectroscopy (XAS). A key parameter for the charge transfer is the ionization potential of FePcFx. A distinct electron transfer from a molecule to a substrate is observed for FePc and FePcF4. From energy-momentum ARPES maps, we suppose that the substrate and FePc-related states hybridize at the interface. This study demonstrates that a controlled tuning of the electronic structure of MoS2 by electron donors is possible, driven by the ionization potential difference between the substrate and the adsorbate.
Charge Transfer from Organic Molecules to Molybdenum Disulfide: Influence of the Fluorination of Iron Phthalocyanine, Katharina Greulich, Axel Belser, Sven Bölke, Peter Grüninger, Reimer Karstens, Marie Sophie Sättele, Ruslan Ovsyannikov, Erika Giangrisostomi, Tamara V. Basova, Darya D. Klyamer, Thomas Chassé, Heiko Peisert, The Journal of Physical Chemistry C, 124 (2020) 16990–16999.