Layer Resolved Cr Oxidation State Modulation in Epitaxial SrFe<sub>0.67</sub>Cr<sub>0.33</sub>O<sub>3−δ</sub> Thin Films
Understanding how doping influences physicochemical properties of ABO<sub>3</sub> perovskite oxides is critical for tailoring their functionalities. In this study, SrFe<sub>0.67</sub>Cr<sub>0.33</sub>O<sub>3-δ</sub> epitaxial thin films were used to examine the effects of Fe and Cr competition on structure and B-site cation oxidation states. The films exhibit a perovskite-like structure near the film/substrate interface, while a brownmillerite-like structure with horizontal oxygen vacancy channels predominates near the surface. Electron energy loss spectroscopy shows Fe remains Fe<sup>3+</sup>, while Cr varies from ∼Cr<sup>3+</sup> (tetrahedral layers) to ∼Cr<sup>4+</sup> (octahedral layers) within brownmillerite phases and becomes ∼Cr<sup>4.5+</sup> in perovskite-like phases. Theoretical simulations indicate that Cr-O bond arrangements and the way oxygen vacancies interact with Cr and Fe drive Cr charge disproportionation. High-valent Cr cations introduce additional densities of states near the Fermi level, reducing the optical bandgap from ∼2.0 eV (SrFeO<sub>2.5</sub>) to ∼1.7 eV (SrFe<sub>0.67</sub>Cr<sub>0.33</sub>O<sub>3-δ</sub>). These findings offer insights into B-site cation doping in the perovskite oxide framework.
Authors
- Zengqing Zhuo (ORCID: https://orcid.org/0000-0001-6602-760X)
- Yingge Du (ORCID: https://orcid.org/0000-0001-9680-1950)
- Steven R. Spurgeon (ORCID: https://orcid.org/0000-0003-1218-839X)
- Mohammad Delower Hossain (ORCID: https://orcid.org/0000-0003-4769-0339)
- Krishna Prasad Koirala (ORCID: https://orcid.org/0000-0002-9137-917X)
- Wanli Yang (ORCID: https://orcid.org/0000-0003-0666-8063)
- Peter V. Sushko (ORCID: https://orcid.org/0000-0001-7338-4146)
- Mark Bowden (ORCID: https://orcid.org/0000-0003-3812-3340)
- Le Wang (ORCID: https://orcid.org/0000-0002-7730-9482)
- Chongmin Wang (ORCID: https://orcid.org/0000-0003-3327-0958)
Institutions
- Pacific Northwest National Laboratory (US)
- Lawrence Berkeley National Laboratory (US)
- University of Washington (US)
- Environmental Molecular Sciences Laboratory (US)
Publication Details
- Journal
- Nano Letters
- Published
- 2024-10-31
- DOI
- https://doi.org/10.1021/acs.nanolett.4c03660
- Citations
- 4
- Primary Topic
- Magnetic and transport properties of perovskites and related materials
- Type
- article
- Field-Weighted Citation Impact
- 0.47
Funders
- U.S. Department of Energy
- U.S. Department of Commerce
- Washington State University
- Office of Science
- Basic Energy Sciences
- Lawrence Berkeley National Laboratory
- Division of Materials Sciences and Engineering