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Lookup NU author(s): Dr Thomas PopeORCiD, Professor Thomas Penfold
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
The evolution of charge carriers in photoexcited room temperature ZnO nanoparticles in solution is investigated using ultrafast ultraviolet photoluminescence spectroscopy, ultrafast Zn K-edge absorption spectroscopy, and ab initio molecular dynamics (MD) simulations. The photoluminescence is excited at 4.66 eV, well above the band edge, and shows that electron cooling in the conduction band and exciton formation occur in <500 fs, in excellent agreement with theoretical predictions. The x-ray absorption measurements, obtained upon excitation close to the band edge at 3.49 eV, are sensitive to the migration and trapping of holes. They reveal that the 2 ps transient largely reproduces the previously reported transient obtained at 100 ps time delay in synchrotron studies. In addition, the x-ray absorption signal is found to rise in ∼1.4 ps, which we attribute to the diffusion of holes through the lattice prior to their trapping at singly charged oxygen vacancies. Indeed, the MD simulations show that impulsive trapping of holes induces an ultrafast expansion of the cage of Zn atoms in <200 fs, followed by an oscillatory response at a frequency of ∼100 cm−1, which corresponds to a phonon mode of the system involving the Zn sub-lattice.
Author(s): Milne CJ, Nagornova N, Pope T, Chen H-Y, Rossi T, Szlachetko J, Gawelda W, Britz A, van Driel T, Sala L, Ebner S, Katayama T, Southworth SH, Doumy G, March AM, Lehmann CS, Mucke M, Iablonskyi D, Kumagai Y, Knopp G, Motomura K, Togashi T, Owada S, Yabashi M, Nielsen MM, Pajek M, Ueda K, Abela R, Penfold TJ, Chergui M
Publication type: Article
Publication status: Published
Journal: Structural Dynamics
Year: 2023
Volume: 10
Online publication date: 03/11/2023
Acceptance date: 06/10/2023
Date deposited: 06/11/2023
ISSN (electronic): 2329-7778
Publisher: AIP Publishing LLC
URL: https://doi.org/10.1063/4.0000204
DOI: 10.1063/4.0000204
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