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O: Fachverband Oberflächenphysik

O 67: Ultrafast Electron Dynamics II

O 67.3: Vortrag

Mittwoch, 19. März 2025, 15:30–15:45, H11

Ultrafast formation of electron polarons in rutile TiO2(110) — •xiang zhang, lukas gierster, and julia stähler — Humboldt-Universität zu Berlin, Institut für Chemie

The electron dynamics at TiO2 surfaces are widely studied, mainly focusing on the defect-induced electronic states [1,2]. Additionally, recent calculations suggest that upon across-bandgap excitation, electron polarons form within 25 fs by trapping of photoexcited electrons inside the deformed lattice [3]. Using time-resolved photoelectron spectroscopy, we observe the instrument response-limited (<30 fs) rise of a photoinduced electron population at 0.3 eV below EF. To elucidate whether this feature originates from polaron formation, experiments are conducted with different laser fluences, photon en- ergies and under varying surface conditions. Based on this, competing mechanism as exciton formation, surface photovoltage effects and band gap renormalization can be excluded. Our results suggest that photoexcitation of the rutile TiO2(110) surface creates small sub-surface polarons within only 30 fs.

Reference:

[1] A. Argondizzo et al. J. Phys. Chem. C 120, 12959-12966(2016).

[2] Y. Zhang et al. J. Phys. Chem. Lett. 10, 5265-5270(2019).

[3] C. Gao et al. J. Phys. Chem. C 125, 27275-27282(2021).

Keywords: ultrafast photoemission spectroscopy; rutile TiO2; defect-induced electronic states; photoexcited electrons; polaron formation