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Title: Ultrafast transient reflectance of epitaxial semiconducting perovskite thin films

Ultrafast pump-probe transient reflectance (TR) spectroscopy was used to study carrier dynamics in an epitaxial perovskite oxide thin film of LaFeO{sub 3} (LFO) with a thickness of 40 unit cells (16 nm) grown by molecular beam epitaxy on (LaAlO{sub 3}){sub 0.3}(Sr{sub 2}AlTaO{sub 6}){sub 0.7} (LSAT). TR spectroscopy shows two negative transients in reflectance with local maxima at ∼2.5 eV and ∼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 (∼200 ps), and slow (∼ 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 ∼10% of photoexcited carriers exist for at least 3 ns. This work illustrates that TR spectroscopy can be performed on thin (<20 nm) 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.
Authors:
; ;  [1] ; ;  [2]
  1. Department of Chemical and Biological Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)
  2. Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States)
Publication Date:
OSTI Identifier:
22311078
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 2; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALUMINATES; ALUMINIUM COMPOUNDS; CARRIERS; ELLIPSOMETRY; FERRITES; LANTHANUM COMPOUNDS; LIFETIME; MOLECULAR BEAM EPITAXY; OXIDES; PEROVSKITE; PHOTOCATALYSIS; PHOTOVOLTAIC EFFECT; RECOMBINATION; SPECTROSCOPY; STRONTIUM COMPOUNDS; TANTALUM COMPOUNDS; THICKNESS; THIN FILMS; TRANSIENTS