Growth and surface modification of LaFeO3 thin films induced by reductive annealing

Brendan T. Flynn, Kelvin H L Zhang, Vaithiyalingam Shutthanandan, Tamas Varga, Robert J. Colby, Richard P. Oleksak, Sandeep Manandhar, Mark H. Engelhard, Scott A. Chambers, Michael A. Henderson, Gregory S. Herman, Suntharampillai Thevuthasan

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4 Citations (Scopus)

Abstract

The mixed electronic and ionic conductivity of perovskite oxides has enabled their use in diverse applications such as automotive exhaust catalysts, solid oxide fuel cell cathodes, and visible light photocatalysts. The redox chemistry at the surface of perovskite oxides is largely dependent on the oxidation state of the metal cations as well as the oxide surface stoichiometry. In this study, LaFeO3 (LFO) thin films grown on yttria-stabilized zirconia (YSZ) was characterized using both bulk and surface sensitive techniques. A combination of in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) demonstrated that the film is primarily textured in the [1 0 0] direction and is stoichiometric. High-resolution transmission electron microscopy measurements show regions that are dominated by [1 0 0] oriented LFO grains that are oriented with respect to the substrates lattice. However, selected regions of the film show multiple domains of grains that are not [1 0 0] oriented. The film was annealed in an ultra-high vacuum chamber to simulate reducing conditions and studied by angle-resolved X-ray photoelectron spectroscopy (XPS). Iron was found to exist as Fe(0), Fe(II), and Fe(III) depending on the annealing conditions and the depth within the film. A decrease in the concentration of surface oxygen species was correlated with iron reduction. These results should help guide and enhance the design of LFO materials for catalytic applications.

Original languageEnglish
Pages (from-to)309-315
Number of pages7
JournalApplied Surface Science
Volume330
DOIs
Publication statusPublished - 1 Mar 2015
Externally publishedYes

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Keywords

  • Angle-resolved
  • LaFeO
  • Lanthanum iron oxide
  • Molecular beam epitaxy
  • Perovskite
  • XPS

ASJC Scopus subject areas

  • Surfaces, Coatings and Films

Cite this

Flynn, B. T., Zhang, K. H. L., Shutthanandan, V., Varga, T., Colby, R. J., Oleksak, R. P., Manandhar, S., Engelhard, M. H., Chambers, S. A., Henderson, M. A., Herman, G. S., & Thevuthasan, S. (2015). Growth and surface modification of LaFeO3 thin films induced by reductive annealing. Applied Surface Science, 330, 309-315. https://doi.org/10.1016/j.apsusc.2015.01.028