SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 76: Plasmonics and Nanooptics III: Light-Matter Interaction and Spectroscopy II

O 76.7: Vortrag

Donnerstag, 30. März 2023, 12:00–12:15, WIL A317

Luminescence from Cu₂O films and bulk crystals in the STM — Alexander Gloystein, Mina Soltanmohammadi, and •Niklas Nilius — Carl von Ossietzky Universität, Institut für Physik, D-26111 Oldenburg, Germany

STM luminescence spectroscopy is employed to compare the optical response of bulk Cu₂O(111) and 1-10 nm thick Cu₂O/Au(111) films. Although both systems share similar structural and electronic properties and expose the same thermodynamically preferred (√3× √3)R30^∘ reconstruction, their luminescence exhibits pronounced differences. The spectra of bulk Cu₂O are dominated by the recombination of free and defect-bound excitons, whereas a unique plasmonic response is detected for the oxide films. The latter arises from the electromagnetic coupling between STM tip and gold support, while the Cu₂O ad-layer exclusively controls the inelastic tunneling rates, i.e., the intensity, but not the spectral signature of the emission. Only upon tunneling into the Cu₂O band gap, a luminescence channel mediated by O vacancies is identified in the oxide film. The talk addresses the question why the unique exciton response of Cu₂O is covered by plasmon excitations even in films as thick as 10 nm.