Regensburg 2025 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 97: Organic Molecules on Inorganic Substrates: Electronic, Optical and Other Properties II
O 97.4: Vortrag
Freitag, 21. März 2025, 11:15–11:30, H6
Second harmonic spectroscopy of Fe-porphyrin/Cu(001) interfaces — •Newsha Vesalimahmoud, Mahendra Kabbinahithlu, Ping Zhou, Uwe Bovensiepen, and Andrea Eschenlohr — University of Duisburg-Essen, Faculty of Physics and CENIDE, Lotharstr. 1, 47057 Duisburg, Germany
When a molecule interacts with a metal surface, metal-molecule interaction induces a rearrangement of their electronic densities, shifting the molecular orbitals relative to the metal’s Fermi level. This study focuses on the FeOEP/Cu(001) interface, using interface-sensitive SHG spectroscopy. We analyze polarization- and wavelength-dependent SHG for varying molecular adsorbate thicknesses on Cu(001) using a fundamental beam in the 500-600 nm range. Polarization-dependent measurements show a higher SHG yield for p-P polarization than s-P SHG, as the intrinsic value of |χzzz(2)| is much larger than |χzxx(2)|. As the number of monolayers increases, P-polarized SHG intensity decreases due to reduced nonlinear susceptibility from less polarizable free electrons, while S-polarized SHG shifts from 4-fold to 2-fold symmetry. The SHG spectra show an intensity peak at 2.17 eV due to a one ω resonance in Cu(001). After adsorption of 2, 5, and 8 monolayers (ML) of FeOEP on Cu(001), the spectral dependence remains similar to the Cu(001) surface, except for an enhancement at 2.21 eV for 5ML and 8ML. This enhancement is attributed to the energetic position of the lowest unoccupied molecular orbital (LUMO) at the FeOEP/Cu(001) interface.
Keywords: second harmonic spectroscopy; molecule/metal interface; porphyrin molecules