Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 31: Poster: Organic Molecules on Inorganic Substrates
O 31.8: Poster
Dienstag, 19. März 2024, 18:00–20:00, Poster C
Measuring and Mapping Molecular Elongation by NC-AFM: The Case of Nonahelicene and Coronene on Ag(110) — •Max Halbauer1, Takashi Kumagai2, Martin Wolf1, and Akitoshi Shiotari1 — 1Fritz-Haber-Institute, Faradayweg 4-6, 14195 Berlin, Germany — 2Institute for Molecular Science, 38 NishigoNaka, Myodaiji, Okazaki 444-8585, Japan
Non-contact atomic force microscopy (NC-AFM) has become a standard tool for the investigation of individual atoms and molecules on surfaces. However, the measurement of elasticity in single molecules and its submolecular resolution have remained as a largely open question. To address this issue, a spring molecule - nonahelicene ([9]H) - was investigated and compared with its flat counterpart - coronene (cor). The molecules were imaged first by high-resolution scanning tunneling microscopy (STM) and NC-AFM on a Ag(110)-surface at cryogenic temperatures (4.8 K), ultrahigh vacuum (UHV) conditions and CO-tips. Interactions of metallic tips with [9]H and cor and the associated elongations were studied then by frequency shift- distance measurements. A novel model for the description of the NC-AFM signals considering an elastic response in the molecular spring was utilized subsequently to rationalize the behavior of both molecules. The spring constant of [9]H was thereby successfully determined to be 5.6 N/m. A position dependent systematic study of the response above the [9]H molecule was performed then to resolve the elastic component with submolecular resolution. The results demonstrate NC-AFM as a powerful tool for the detection of deformation on the atomic scale.
Keywords: Atomic Force Microscopy; Elasticity; Force Distance curves; helicene; single molecule