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O: Fachverband Oberflächenphysik

O 45: Organic molecules on inorganic substrates: Adsorption and growth – Poster

O 45.2: Poster

Dienstag, 10. März 2026, 14:00–16:00, P2

Importance of Electrostatic Effects for Interpretation of X-ray Photoemission Spectra of Self-Assembled Monolayers — •Michael Zharnikov — Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany

The subject of this contribution is electrostatic effects in X-ray photoemission (XP) from self-assembled monolayers (SAMs), which are application-relevant ultrathin molecular films, coupled to the substrate by a suitable anchoring group. Whereas, in most cases, the standard concept of chemical shift is fully sufficient to describe XP spectra of these systems, consideration of electrostatic effects is frequently necessary for their proper interpretation. Due to the insulating character of the SAM matrix, decoupled electronically from the substrate, the introduction of a dipolar "sheet" at the SAM-substrate interface or within this matrix creates a potential discontinuity, shifting the energy levels above the "sheet" with respect to those below it. This shift is reflected then in the matrix-related spectra, resulting in shifts and splitting of the characteristic photoemission peaks. Representative examples in this context underline the importance of electrostatic effects in photoemission and suggest that they should be considered on equal footing with the chemical shift.

Keywords: self-assembled monolayers; X-ray photoemission; chemical shift; electrostatic effects