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Lookup NU author(s): Professor Thomas Penfold
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Nanostructures of transition metal oxides, such as zinc oxide, have attracted considerable interest for solar-energy conversion and photocatalysis. Both applications are sensitive to the transport and trapping of photoexcited charge carriers. The probing of electron trapping has recently become possible using time-resolved element-sensitive methods, such as X-ray spectroscopy. However, valence-band-trapped holes have so far escaped observation. Herein we use X-ray absorption spectroscopy combined with a dispersive X-ray emission spectrometer to probe the charge carrier relaxation and trapping processes in zinc oxide nanoparticles after above band-gap photoexcitation. Our results, supported by simulations, demonstrate that within 80 ps, photoexcited holes are trapped at singly charged oxygen vacancies, which causes an outward displacement by ~15% of the four surrounding zinc atoms away from the doubly charged vacancy. This identification of the hole traps provides insight for future developments of transition metal oxide-based nanodevices.
Author(s): Penfold TJ, Szlachetko J, Santomauro FG, Britz A, Gawelda W, Doumy G, March AM, Southworth SH, Rittmann J, Abela R, Chergui M, Milne CJ
Publication type: Article
Publication status: Published
Journal: Nature Communications
Print publication date: 02/02/2018
Acceptance date: 01/01/2018
Date deposited: 05/02/2018
ISSN (electronic): 2041-1723
Publisher: Nature Publishing Group
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