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O: Fachverband Oberflächenphysik

O 43: Scanning probe microscopy: light matter interaction at atomic scales – Poster

O 43.1: Poster

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

Modelling the near-field enhancement for tip-enhanced photoluminescence on non-conductive layers — •Jinhui Guo and Laerte Patera — Department of Physical Chemistry, University of Innsbruck, 6020 Innsbruck, Austria

While scanning tunnelling microscopy (STM)-based tip-enhanced photoluminescence (TEPL) has been demonstrated for molecules adsorbed on 2-3 monolayers (ML) of NaCl/Ag(111) [1], nonradiative quenching due to charge tunnelling through the insulating layer is expected to affect the exciton lifetime. Employing sufficiently thick insulating layers (> 14 ML) strongly suppresses electron tunnelling [2], potentially preserving the photoexcited state. However, such thick insulating layers are incompatible with STM operation, making atomic force microscopy (AFM) an ideal choice. To elucidate the field enhancement in AFM-based TEPL experiments, we performed three-dimensional finite element method (3D-FEM) simulations [3] for various AFM Cu tip geometries and Cu substrates with and without NaCl layers up to 20 ML. Our results indicate that below the tip, a pronounced electric field enhancement in the plane parallel to the sample surface (E_{/ /}) persists even on a 20 ML-thick NaCl layer. This effect arises mainly from the reduced screening of E_{/ /} within the NaCl layers compared to the metallic Cu substrate. These findings support the exploitation of non-conductive layers for TEPL experiments.

[1] J. Doležal et al., Nano Lett. 2024, 24, 1629-1634. [2] W. Steurer et al., Nat. Commun. 2015, 6, 8353. [3] COMSOL Multiphysics^® v. 6.3. www.comsol.com. COMSOL AB, Stockholm, Sweden.

Keywords: atomic force microscopy; tip-enhanced photoluminescence; thick insulating layers; 3D-FEM simulation; near-field enhancement