Resistive Switching Memory Based on Ferroelectric Polarization Reversal at Schottky-like BiFeO 3 Interfaces
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Resistive Switching Memory Based on Ferroelectric Polarization Reversal at Schottky-like BiFeO3 Interfaces Atsushi Tsurumaki-Fukuchi, Hiroyuki Yamada and Akihito Sawa National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8562, Japan ABSTRACT We have fabricated a ferroelectric resistive switching device of Pt/Bi1-δFeO3 (BFO)/SrRuO3 (SRO) in which the conductivity of BFO layer was controlled by changing the Bi-deficiency concentration. The devices showed a bipolar-type resistive switching effect, i.e., zero-crossing hysteretic current–voltage (I–V) characteristics. In addition, the I–V characteristics in both high and low resistance states are nonlinear, which can avoid a read-error problem in a passive crossbar memory array. Resistive switching characteristics measured in pulse-voltage mode revealed that the resistance values in low resistance states vary with the amplitude and duration time of the pulsed-voltage stresses, indicating possibility of multilevel switching. On the basis of the experimental results, we discuss the potential of the Pt/BFO/SRO device for application in a large-capacity nonvolatile memory. INTRODUCTION Resistive switching phenomena in transition-metal oxides is attracting great attention because of their possible application to nonvolatile memory devices, i.e., resistance random access memory (ReRAM) [1,2]. In terms of driving mechanism, recent studies revealed that the resistive switching phenomena can be categorized into two broad types: thermochemical and valence-change types. In thermochemical type switching, Joule heating induces local redox reactions of a conductive filament. On the other hand, electromigration of oxygen vacancies induces changes in the valence state of cations in a metal oxide in the valence-change type. However, there is concern for memory reliability in both the mechanisms because chemical alteration of materials is inevitably induced by switching processes. As a solution of this problem, resistive switching based on an electronic mechanism is being considered. Because ferroelectric polarization reversal is an intrinsically fast and nonvolatile phenomenon and does not induce a chemical alteration, ferroelectric resistive switching effect is particularly attractive. Indeed, the resistive switching devices consisting of ferroelectric oxides have been studied [3-5]. However, there are few reports on investigation of switching characteristics in the pulse-voltage mode for ferroelectric resistive switching devices, which is needed for memory applications. In this study, we have fabricated ferroelectric resistive switching devices consisting of a multiferroic oxide BiFeO3 and investigated in detail their resistive switching characteristics in the pulse-voltage mode. Recently, we have reported that the resistive switching observed in the device with a capacitor-like structure of Pt/Bi1-δFeO3 (BFO)/SrRuO3 (SRO) is attributable to polarization reversal in the BFO layer and the device shows promising characteristics for use as
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