Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 50: Poster Organic Molecules on Inorganic Substrates: Adsorption and Growth

O 50.5: Poster

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

Long range ordering of molecular layers on Ag(110) — •Ravi Priya, Weishan Wu, and Peter Jakob — Department of Physics, Philipps University of Marburg, Germany

Single domain molecular layers have been explored on the non-hexagonal Ag(110) substrate in terms of their long-range ordering using SPA-LEED and vibrational signature using high-resolution FT-IRAS. The absence of rotational domains for fcc(110) metal substrates allows for growing layers with uniform azimuthal orientation of deposited molecules. We have investigated various molecules and configurations that may form single domain molecular layers (including mirror domains). Specifically, monolayers of PTCDA, NTCDA, and regio-selectively substituted pentacene species (pentacene (PEN), pentacene-quinone (P2O), pentacene-tetrone (P4O), quinacridone (QA)) were deposited on Ag(110) and examined in terms of their structure using SPA-LEED, and their vibrational signature using IR - spectroscopy. Among them, PTCDA, NTCDA, PEN, and QA have been found to form parallel-oriented, single domain structures. For QA two novel heterochiral phases are found after annealing, in addition to the single-domain homochiral phase present T < 500K. For P2O and P4O, steric hindrance and hydrogen bonding lead to the formation of 1D islands and 2D islands, respectively, at sub-monolayer coverages. Another finding refers to the increased molecule - metal interaction on Ag(110) vs. Ag(111) that leads to an extra energy (down)shift of the LUMO, thereby having a significant impact on interfacial dynamic charge transfer (IDCT) of vibrational modes.

Keywords: Pentacenequinone; Pentacenetetrone; IRAS; SPA-LEED; PTCDA