Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 49: Poster Session - Organic Molecules on Inorganic Substrates: Electronic, Optical and Other

O 49.1: Poster

Tuesday, March 17, 2020, 18:15–20:00, P2/EG

Sum frequency spectroscopy of o-, m- and p-Methylbenzylphos-phonic acid on α-aluminium oxide — •Tim Lämmerzahl, Matthias Linke, Damian Firla, and Eckart Hasselbrink — Universität Duisburg-Essen, Essen, Germany

Self-assembled molecular monolayers (SAMs) are applied to engineer surface properties in a defined way which makes SAMs interesting for numerous applications. While there have been many studies on prominent SAMs e.g. thiols on gold, the existing knowledge on phosphonic acid (PA) SAMs still lacks behind. A very prominent substrate for PA SAMs is aluminum oxide, due to its use in a wide range of research applications like organic field-effect sensors and in different fields of industry e.g. aerospace. The surface sensitive vibrational sum frequency spectroscopy (vSFS) is well suited for the characterization of such surfaces. To this note we studied different isomers of methylbenzylphosphonic acid (MBPA) via vSFS in the spectral range of the C-H vibrations. We were able to show that due to the selection rules for sum frequency generation, different bands are observed for the three possible substitution patterns of MBPA in the spectral range of the aromatic C-H vibrations. When comparing the spectra in the spectral region of aliphatic C-H vibrations, a clear difference between the isomers can be shown. This study provides interesting insights into the orientation of different constitutional isomers on the surface.