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Epitaxial Brownmillerite Oxide Thin Films for Reliable Switching Memory Susant Kumar Acharya, Raveendra Venkata Nallagatla, Octolia Togibasa, Bo Wha Lee, Chunli Liu, Chang Uk Jung, Bae Ho Park, Ji-Yong Park, Yunae Cho, Dong-Wook Kim, Janghyun Jo, Deok-Hwang Kwon, Miyoung Kim, Cheol Seong Hwang, and Seung Chul Chae ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b00647 • Publication Date (Web): 09 Mar 2016 Downloaded from http://pubs.acs.org on March 12, 2016
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ACS Applied Materials & Interfaces
Epitaxial Brownmillerite Oxide Thin Films for Reliable Switching Memory Susant K. Acharya †, Nallagatla V. Raveendra†, Octolia Togibasa†, Bo W. Lee†, Chunli Liu†, Chang U. Jung †*, Bae H. Park‡, Ji-Yong Park§, Yunae Cho⊥, Dong-Wook Kim⊥, Janghyun Jo∥, Deok-Hwang Kwon∥, Miyoung Kim∥, Cheol S. Hwang=, and Seung C. Chae# † Department of Physics and Oxide Research Centre, Hankuk University of Foreign Studies, Yongin 449-791, Korea ‡ Department of Physics and Division of Quantum Phases and Devices, Konkuk University, Seoul 143-791, Korea § Department of Physics and Division of Energy Systems Research, Ajou University, Suwon 443-749, Korea ⊥ Department of Physics, Ewha Womans University, Seoul 120-750, Korea ∥ Department of Material Science and Engineering, Seoul National University, Seoul 151-747, Korea = Department of Material Science and Engineering and Inter-University Semiconductor Research Center, Seoul National University, Seoul 151-744, Korea # Department of Physics Education, Seoul National University, Seoul 151-748, Korea KEYWORDS: Brownmillerite structure, SrFeOx thin film, atomically smooth surface, RRAM, uniform switching parameters
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[email protected] ABSTRACT Resistive switching memory, which is mostly based on polycrystalline thin films, suffers from wide distributions in switching parameters—including set voltage, reset voltage, and resistance—in their low- and high-resistance states. One of the most commonly used methods to overcome this limitation is to introduce inhomogeneity. By contrast, in this paper, we obtained uniform resistive switching parameters and sufficiently low forming voltage by maximizing the uniformity of an epitaxial thin film. To achieve this result, we deposited an SrFeOx/SrRuO3 heteroepitaxial structure onto an SrTiO3 (001) substrate by pulsed laser deposition, then we deposited an Au top electrode by electron-beam evaporation. This device exhibited excellent bipolar resistance switching characteristics, including a high ON/OFF ratio, narrow distribution of key switching parameters, and long data retention time. We interpret these phenomena in terms of a local, reversible phase transformation in the SrFeOx film between brownmillerite and perovskite structures. Using the brownmillerite structure and atomically uniform thickness of the heteroepitaxial SrFeOx thin film, we overcame two major hurdles in the development of resistive random-access memory devices: high forming voltage and broad distributions of switching parameters. INTRODUCTION Transition metal–oxide resistance switching random access memory (RRAM), which is based on reversible changes between a high resistance state (HRS) and a low resistance state (LRS), has recently attracted a great deal of scientific and commercial interest because of its high operational speed (
