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Download filePhotoexcited Small Polaron Formation in Goethite (α-FeOOH) Nanorods Probed by Transient Extreme Ultraviolet Spectroscopy
journal contribution
posted on 2018-07-09, 00:00 authored by Ilana
J. Porter, Scott K. Cushing, Lucas M. Carneiro, Angela Lee, Justin C. Ondry, Jakob C. Dahl, Hung-Tzu Chang, A. Paul Alivisatos, Stephen R. LeoneSmall polaron formation
limits the mobility and lifetimes of photoexcited
carriers in metal oxides. As the ligand field strength increases,
the carrier mobility decreases, but the effect on the photoexcited
small polaron formation is still unknown. Extreme ultraviolet transient
absorption spectroscopy is employed to measure small polaron formation
rates and probabilities in goethite (α-FeOOH) crystalline nanorods
at pump photon energies from 2.2 to 3.1 eV. The measured polaron formation
time increases with excitation photon energy from 70 ± 10 fs
at 2.2 eV to 350 ± 30 fs at 2.6 eV, whereas the polaron formation
probability (85 ± 10%) remains constant. By comparison to hematite
(α-Fe2O3), an oxide analogue, the role
of ligand composition and metal center density in small polaron formation
time is discussed. This work suggests that incorporating small changes
in ligands and crystal structure could enable the control of photoexcited
small polaron formation in metal oxides.