Complementary Resistive Switching and Synaptic-Like Memory Behavior in an Epitaxial SrFeO2.5 Thin Film through Oriented Oxygen-Vacancy Channels

Venkata Raveendra Nallagatla; Jihun Kim; Kyoungjun Lee; Seung Chul Chae; Cheol Seong Hwang; Chang Uk Jung

doi:10.1021/acsami.0c10910

Complementary Resistive Switching and Synaptic-Like Memory Behavior in an Epitaxial SrFeO_2.5 Thin Film through Oriented Oxygen-Vacancy Channels

ACS Appl Mater Interfaces. 2020 Sep 16;12(37):41740-41748. doi: 10.1021/acsami.0c10910. Epub 2020 Aug 31.

Authors

Venkata Raveendra Nallagatla¹, Jihun Kim², Kyoungjun Lee³, Seung Chul Chae³, Cheol Seong Hwang², Chang Uk Jung¹

Affiliations

¹ Department of Physics and Memory and Catalyst Research Center, Hankuk University of Foreign Studies, Yongin 17035, Korea.
² Department of Material Science and Engineering and Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826, Korea.
³ Department of Physics Education, Seoul National University, Seoul 08826, Korea.

PMID: 32799524
DOI: 10.1021/acsami.0c10910

Abstract

Oxygen-vacancy-ordered brownmillerite oxides offer a reversible topotactic phase transition by significantly varying the oxygen stoichiometry of the material without losing its lattice framework. This phase transition leads to substantial changes in the physical and chemical properties of brownmillerite oxides, including electrical and ion conductivity, magnetic state, and oxygen diffusivity. In this study, the variations in the resistive switching mode of the epitaxial brownmillerite SrFeO_2.5 thin film in the device were studied by systematically controlling the oxygen concentration, which could be varied by changing the compliance current during the first electroforming step. Depending on the compliance current, the SrFeO_2.5 devices exhibited either low-power bipolar resistive switching or complementary resistive switching behaviors. A physical model based on the internal redistribution of oxygen ions between the interfaces with the top and the bottom electrodes was developed to explain the complementary resistive switching behavior. This model was experimentally validated using impedance spectroscopy. Finally, the gradual conductance variation in the brownmillerite SrFeO_2.5 thin films was exploited to realize synaptic learning.

Keywords: brownmillerite structure; complementary resistive switching; growth orientation; oxygen-vacancy channels; synaptic memory; topotactic phase transition.