Berlin 2024 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 80: Scanning Probe Microscopy: Light Matter Interaction at Atomic Scales II
O 80.2: Vortrag
Donnerstag, 21. März 2024, 10:45–11:00, MA 041
Excitation mechanism for STM-induced luminescence — •Song Jiang1, Tomáš Neuman2, Rémi Bretel2, Alex Boeglin1, Fabrice Scheurer1, Eric Le Moal2, and Guillaume Schull1 — 1Université de Strasbourg, CNRS, IPCMS, UMR 7504, F-67000 Strasbourg, France — 2Institut des Sciences Moléculaires d’Orsay (ISMO), UMR 8214, CNRS, Université Paris-Saclay, 91405 Orsay Cedex, France
Fluorescence of neutral and charged molecules has been reported with subnanometer resolution in scanning tunneling microscope induced-luminescence (STML) experiments over the last years. Despite these significant developments, the detailed mechanisms of STML of individual molecules remained to be fully understood. Here, we proposed a “universal” model relying on successive carrier tunneling events that is based on a systematic experimental STML study of quinacridone (QA) molecules adsorbed on four-monolayer (4 ML) NaCl/Ag(111). Based on a comparison between the spatial, bias voltage, and tunneling current dependences of the charged and neutral emission, and on conductance data, a many-body description of the system is set. It reveals that four different charged states of QA (QA−, QA0, QA+, and QA2+), involving three different spin multiplicities, can be populated within a single voltage sweep. This excitation mechanism is backed up by data obtained for QA deposited on NaCl/Au(111) where the ground state of the molecule is a doubly positively charged singlet state (S2+). This model bears a universal character that can be applied to STML experiments dealing with charged and neutral molecules.
Keywords: Electroluminescence; Many-body description; Excited states; STML; Charge transfer