Nanoscale Topotactic Phase Transformation in SrFeOx Epitaxial Thin Films for High-Density Resistive Switching Memory

Junjiang Tian; Haijun Wu; Zhen Fan; Yang Zhang; Stephen J Pennycook; Dongfeng Zheng; Zhengwei Tan; Haizhong Guo; Pu Yu; Xubing Lu; Guofu Zhou; Xingsen Gao; Jun-Ming Liu

doi:10.1002/adma.201903679

Nanoscale Topotactic Phase Transformation in SrFeO_x Epitaxial Thin Films for High-Density Resistive Switching Memory

Adv Mater. 2019 Dec;31(49):e1903679. doi: 10.1002/adma.201903679. Epub 2019 Oct 22.

Authors

Junjiang Tian^{1

2}, Haijun Wu³, Zhen Fan^{1

2}, Yang Zhang³, Stephen J Pennycook³, Dongfeng Zheng¹, Zhengwei Tan¹, Haizhong Guo⁴, Pu Yu⁵, Xubing Lu¹, Guofu Zhou^{2

6}, Xingsen Gao¹, Jun-Ming Liu^{1

7}

Affiliations

¹ Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, 510006, China.
² Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, 510006, China.
³ Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore.
⁴ School of Physical Engineering, Zhengzhou University, Zhengzhou, 450001, China.
⁵ State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing, 100084, China.
⁶ National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, 510006, China.
⁷ Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.

PMID: 31639262
DOI: 10.1002/adma.201903679

Abstract

Resistive switching (RS) memory has stayed at the forefront of next-generation nonvolatile memory technologies. Recently, a novel class of transition metal oxides (TMOs), which exhibit reversible topotactic phase transformation between insulating brownmillerite (BM) phase and conducting perovskite (PV) phase, has emerged as promising candidate materials for RS memories. Nevertheless, the microscopic mechanism of RS in these TMOs is still unclear. Furthermore, RS devices with simultaneously high density and superior memory performance are yet to be reported. Here, using SrFeO_x as a model system, it is directly observed that PV SrFeO₃ nanofilaments are formed and extend almost through the BM SrFeO_2.5 matrix in the ON state and are ruptured in the OFF state, unambiguously revealing a filamentary RS mechanism. The nanofilaments are ≈10 nm in diameter, enabling to downscale Au/SrFeO_x /SrRuO₃ RS devices to the 100 nm range for the first time. These nanodevices exhibit good performance including ON/OFF ratio as high as ≈10⁴ , retention time over 10⁵ s, and endurance up to 10⁷ cycles. This study significantly advances the understanding of the RS mechanism in TMOs exhibiting topotactic phase transformation, and it also demonstrates the potential of these materials for use in high-density RS memories.

Keywords: SrFeOx; nanofilaments; resistive switching; topotactic phase transformation.

Abstract

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