Regensburg 2019 – scientific programme
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O: Fachverband Oberflächenphysik
O 38: Organic Molecules on Inorganic Substrates II: Electronic Properties and Charge Transfer
O 38.1: Talk
Tuesday, April 2, 2019, 14:00–14:15, H24
Electronic properties of NiOEP on copper: a molecular orbital tomography study — •H. Sturmeit1, G. Zamborlini1, S. Ponzoni1, M. Jugovac2, V. Feyer2, C. M. Schneider2, and M. Cinchetti1 — 1TU Dortmund, 44227 Dortmund, Germany — 2Forschungszentrum Jülich, 52428 Jülich, Germany
π-conjugated organic molecules are considered a valuable alternative to inorganic semiconductors as their electronic, optical and magnetic properties can be tailored at the atomic level. Supporting organic films with metal substrates within an organic-based device, may lead to chemical reactions, hybridization, and/or charge transfer at the metal/organic interface, ultimately affecting the device performance. Recently, this has been shown for nickel tetraphenylporphyrin (NiTPP) evaporated on Cu(100), whose frontier orbitals get partially filled up to the LUMO+3 [Zamborlini et al, Nat. Comm. 8, 335, 2017] due to a consistent charge transfer at the interface. In the present work, we studied the impact of the peripheral substituents of the porphyrin macrocycle on the charge transfer. To achieve this goal, nickel octaethylporphyrin (NiOEP) molecules, where the four phenyl ligands are replaced with eight ethyl terminations in the β-positions of the pyrrole moieties, were sublimated on the (100) copper surface. The overall energy level alignment at the metal/organic interface was characterized by means of molecular orbital tomography. Our preliminary measurements show that changing the periphery does not strongly influence the overall charge transfer: the LUMO+3 remains partially filled while shifting its energetic position by a few tens of meVs.