Layer-resolved ultrafast extreme ultraviolet measurement of hole transport in a Ni-TiO₂-Si photoanode
Abstract
Metal oxide semiconductor junctions are central to most electronic and optoelectronic devices, but ultrafast measurements of carrier transport have been limited to device-average measurements. Here, charge transport and recombination kinetics in each layer of a Ni-TiO₂-Si junction is measured using the element specificity of broadband extreme ultraviolet (XUV) ultrafast pulses. After silicon photoexcitation, holes are inferred to transport from Si to Ni ballistically in ~100 fs, resulting in characteristic spectral shifts in the XUV edges. Meanwhile, the electrons remain on Si. After picoseconds, the transient hole population on Ni is observed to back-diffuse through the TiO₂, shifting the Ti spectrum to a higher oxidation state, followed by electron-hole recombination at the Si-TiO₂ interface and in the Si bulk. Electrical properties, such as the hole diffusion constant in TiO₂ and the initial hole mobility in Si, are fit from these transient spectra and match well with values reported previously.
Additional Information
© 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Submitted 8 July 2019; Accepted 8 January 2020; Published 3 April 2020. The authors gratefully acknowledge financial support provided by the U.S. Air Force Office of Scientific Research (grant no. FA9550-14-1-0154 and FA9550-19-1-0314). The transient absorption measurements were done using a previously built instrument that is funded and has personnel supported (I.J.P.) by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under contract no. DEAC02-05-CH11231, within the Physical Chemistry of Inorganic Nanostructures Program (KC3103). S.K.C. acknowledges support by the Department of Energy Office of Energy Efficiency and Renewable Energy (EERE) Postdoctoral Research Award under the EERE Solar Energy Technologies Office. Author contributions: S.K.C., M.E.V., and S.R.L. designed the study. S.K.C., I.J.P., and A.L. performed the transient XUV measurements, and S.K.C. performed the excited-state modeling and data analysis. B.R.d.R., B.M.M., and M.E.V. were responsible for sample fabrication, and S.S. performed the sample characterization. S.K.C., I.J.P., B.R.d.R., A.L., B.M.M., S.S., M.E.V., and S.R.L. wrote and revised the manuscript. The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.Attached Files
Published - eaay6650.full.pdf
Supplemental Material - aay6650_SM.pdf
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Additional details
- PMCID
- PMC7124930
- Eprint ID
- 102544
- Resolver ID
- CaltechAUTHORS:20200415-073542709
- FA9550-14-1-0154
- Air Force Office of Scientific Research (AFOSR)
- FA9550-19-1-0314
- Air Force Office of Scientific Research (AFOSR)
- DE-AC02-05-CH11231
- Department of Energy (DOE)
- KC3103
- Department of Energy (DOE)
- Created
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2020-04-15Created from EPrint's datestamp field
- Updated
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2022-02-15Created from EPrint's last_modified field