SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 10: Organic Molecules on Inorganic Substrates II: Electronic, Optical and Other Properties II

O 10.4: Vortrag

Montag, 27. März 2023, 16:00–16:15, CHE 89

Charge-induced symmetry breaking in the adsorption configuration of C60 layers on h-BN/Ni(111) — •Max Bommert, Roland Widmer, Néstor Diez, Bruno Schuler, and Oliver Gröning — Empa * Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland

Hexagonal Boron Nitride (h-BN) and Nickel's (111) surface share a nearly perfectly matching lattice constant. Consequently, monolayer h-BN can be grown commensurately on Ni(111) without exhibiting a Moiré superstructure like on many other h-BN/transition metal systems. Nevertheless, upon adsorption at room temperature and scanning tunneling microscopy (STM) imaging at 5K, we observe a complex, geometrically frustrated adsorption pattern for sub-monolayer C60 coverages. The fullerenes form large molecular islands with a distinct striped pattern that we can identify as C60 adsorbed in different orientations. We use scanning tunneling spectroscopy (STS) to resolve the lowest unoccupied molecular orbitals (LUMO) of the C60. Tip-induced manipulation of single molecules affects the LUMO energy of neighboring molecules. Based on our STS investigations, we propose a significant charge transfer from the substrate to specific C60 and the associated electrostatic repulsion to be a driving force in forming the stripe pattern. We rationalize the latter by Monte Carlo simulations of the C60 lattice, considering the various contributions to the intermolecular and molecule-substrate interactions. Our results deepen the understanding of molecular adsorption and charge transfer processes, which are crucial for developing organic-inorganic hybrid devices.