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O: Fachverband Oberflächenphysik

O 9: Organic molecules on inorganic substrates: electronic, optical and other properties I

O 9.7: Vortrag

Montag, 9. März 2026, 16:30–16:45, HSZ/0201

Accessing Energetically Restricted Optical Transitions in a Single Free-Base Porphyrin Molecule — •Eve Ammerman, Nils Krane, and Bruno Schuler — Empa - nanotech@surfaces Laboratory, 8600 Dübendorf, Switzerland

Charge transfer between a single molecule and the electrodes of an STM leads to a series of excitation and relaxation processes, including radiative relaxation from the molecule's optically active excited states. Utilizing the STM tunnel junction in electroluminescence experiments enables optical characterization on sub-molecular length-scales. However, the electroluminescence phenomenon is constrained by the alignment of ionization and optical state energies. Here, we show how positive ion resonance energy of a free-base tetrabenzoporphyrin (H2TBP) can be tuned relative to the optical emission energy through local gating by the STM tunnel junction or by work function engineering. The tuning of the energy level alignment allows us to produce optical emission from H2TBP on Ag(111), where electroluminescence is energetically restricted, or on Ag(110) where the molecule becomes bright.

Keywords: STML; Porphyrin; scanning tunneling microscopy; optical spectroscopy