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O: Fachverband Oberflächenphysik

O 78: Poster Session - Focus Session: Functional Molecules at Surfaces - Motion and Intramolecular Processes

O 78.1: Poster

Mittwoch, 18. März 2020, 18:15–20:00, P2/EG

The influence of the screening towards the properties of phthalocyanine monolayer structures — •T.T.Nhung Nguyen, T.N.H. Nguyen, T. Sollfrank, and C. Tegenkamp — TU Chemnitz, Germany

Proximity effects due to molecular monolayers on two-dimensional materials, e.g. on epitaxial graphene, is a promising approach to modify the properties of the delocalized charge carriers. Thereby, long-range dispersing forces between the molecules and of the molecular film with the substrate provide a high degree of flexibility to realize various phases. Moreover, the concomitant screening of the substrate adds a further degree of freedom to alter the properties of the molecular film. Using STM/STS, we investigated the electronic properties of shuttlecock-like PbPc and planar magnetic MnPc on epitaxial graphene on SiC(0001) and compared with results on highly oriented pyrolytic graphite (HOPG). The incommensurate ratio of the graphene lattice with the molecular size fosters the growth of densely packed and chiral PbPc monolayers, with similar lattice parameters on monolayer graphene (MLG) and quasi-free monolayer graphene (QFMLG). The pronounced difference of the electronic structure is related to the different dielectric screening. On contrast, magnetic MnPc on MLG shows zig-zag like structures coexisting with a square unit cell, seen for PbPc. Such effects were not found for Pc/HOPG despite the same surface structure of graphene and graphite. Apparently, the dielectric screening of the 2D and 3D versions of the C-sp2 allotrope is different and modifies the molecular interaction scheme.