Charge carrier dynamics of anatase TiO2 probed by extreme ultraviolet reflection-absorption spectroscopy

Hruska, Emily B.

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https://hdl.handle.net/2142/104347 Copy

Description

Title

Charge carrier dynamics of anatase TiO2 probed by extreme ultraviolet reflection-absorption spectroscopy

Author(s)

Hruska, Emily B.

Contributor(s)

• Baker, Robert
• Husek, Jakub

Issue Date

2019-06-18

Keyword(s)

High-harmonic generation and XUV spectroscopy

Abstract

Materials with improved catalytic efficiency can be designed based on a more thorough understanding of the excited state dynamics that mediate energy transfer and drive charge separation. High harmonic generation can produce ultrafast pulses in the extreme ultraviolet (XUV) region, enabling the use of XUV reflection-absorption (XUV-RA) spectroscopy to analyze signatures of photoexcited electrons and holes separately. From XUV-RA experiments on anatase TiO$_{}$, it is shown that, for the first 800 fs after photoexcitation there is an apparent quantum beating at 417 \wn. This frequency is consistent with coupling between a free carrier state and a large polaron state, which has been previously observed in TiO$_{2}$. Following the initial dynamic equilibrium between these two states, the electron localizes to a more energetically stable Ti$^{3+}$ defect state 1 eV below the conduction band within 1.22 ps. We hypothesize that the strong electron-phonon coupling leading to the observed beating may be the result of Ti$^{3+}$ defect states which we show are prevalent in this material. To investigate this hypothesis, we are now performing measurements on stoichiometric TiO$_{2}$ with Ti$^{3+}$ defects removed. These ongoing experiments on defect-free TiO$_{2}$ will provide a more complete understanding of the role the Ti$^{3+}$ defects play in the charge carrier kinetics of this catalytically relevant material.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/104347

DOI

https://doi.org/10.15278/isms.2019.TK06

Copyright and License Information

Copyright 2019 Emily B. Hruska

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