Overlayer deposition-induced control of oxide ion concentration in SrFe0.5Co0.5O2.5 oxygen sponges

Joonhyuk Lee; Younghak Kim; Jinhyung Cho; Hiromichi Ohta; Hyoungjeen Jeen

doi:10.1039/d1ra06378b

Overlayer deposition-induced control of oxide ion concentration in SrFe_0.5Co_0.5O_2.5 oxygen sponges

RSC Adv. 2021 Sep 29;11(51):32210-32215. doi: 10.1039/d1ra06378b. eCollection 2021 Sep 27.

Authors

Joonhyuk Lee¹, Younghak Kim², Jinhyung Cho³, Hiromichi Ohta⁴, Hyoungjeen Jeen^{1

5}

Affiliations

¹ Department of Physics, Pusan National University Busan 46241 Korea hjeen@pusan.ac.kr.
² Pohang Accelerator Laboratory, Pohang University of Science and Technology Pohang 37673 Korea.
³ Department of Physics Education, Pusan National University Busan 46241 Korea.
⁴ Research Institute for Electronic Science, Hokkaido University Sapporo 001-0020 Japan hiromichi.ohta@es.hokudai.ac.jp.
⁵ Research Center for Dielectric and Advanced Matter Physics, Pusan National University Busan 46241 Korea.

Abstract

Controlling the oxide ion (O^2-) concentration in oxides is essential to develop advanced ionic devices, i.e. solid oxide fuel cells, smart windows, memory devices, energy storage devices, and so on. Among many oxides several transition metal (TM)-based perovskite oxides show high oxide ion conductivity, and their physical properties show high sensitivity to the change of the oxide ion concentration. Here, the change in the oxide ion concentration is shown through the overlayer deposition on the SrFe_0.5Co_0.5O_2.5 (SFCO) oxygen sponge film. We grew SFCO films followed by the deposition of two kinds of complex oxide films under exactly the same growth conditions, and observed the changes in the crystal structure, valence states, and magnetic ground states. As the NSMO overlayer grows, strong evidence of oxidation at the O K edge is shown. In addition, the Fe⁴⁺ feature is revealed, and the electron valence state of Co increased from 3 to 3.25. The oxide ion concentration of SFCO changes during layer growth due to oxidation or reduction due to differences in chemical potential. The present results might be useful to develop advanced ionic devices using TM-based perovskite oxides.