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Ultrafast transient reflectance of epitaxial semiconducting perovskite thin films
Journal article   Peer reviewed

Ultrafast transient reflectance of epitaxial semiconducting perovskite thin films

S. Y. Smolin, M. D. Scafetta, G. W. Guglietta, J. B. Baxter and S. J. May
Applied physics letters, v 105(2), p22103
14 Jul 2014
DOI: https://doi.org/10.1063/1.4890241

Abstract

Physical Sciences Physics Physics, Applied Science & Technology
Ultrafast pump-probe transient reflectance (TR) spectroscopy was used to study carrier dynamics in an epitaxial perovskite oxide thin film of LaFeO3 (LFO) with a thickness of 40 unit cells (16 nm) grown by molecular beam epitaxy on (LaAlO3)(0.3)(Sr2AlTaO6)(0.7) (LSAT). TR spectroscopy shows two negative transients in reflectance with local maxima at similar to 2,5 eV and similar to 3.5 eV which correspond to two optical transitions in LFO as determined by ellipsometry. The kinetics at these transients were best fit with an exponential decay model with fast (5-40 ps), medium (similar to 200 ps), and slow (similar to 3 ns) components that we attribute mainly to recombination of photoexcited carriers, Moreover, these reflectance transients did not completely decay within the observable time window, indicating that similar to 10% of photoexcited carriers exist for at least 3 ns. This work illustrates that TR spectroscopy can be performed on thin (<20 am) epitaxial oxide films to provide a quantitative understanding of recombination lifetimes, which are important parameters for the potential utilization of perovskite films in photovoltaic and photocatalytic applications. (C) 2014 AIP Publishing LLC.

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