Next-generation Nonvolatile Memory Research Articles

(Invited, Digital Presentation) 50 Ns Ultrafast Memory Operation in 2D Heterostructured Non-Volatile Memory Device

2D heterostructures have been extensively investigated as next-generation non-volatile memory (NVM) devices. In the last decade, drastic performance improvements and further advanced functionalities have been demonstrated. However, this progress is not sufficiently supported by the understanding of their operations, obscuring the material and device structure design policy. Here, detailed operation mechanisms are elucidated by exploiting the floating gate voltage (V FG) trajectory measurements [1,2]. Systematic comparisons of MoTe2, WSe2, and MoS2 channel devices revealed that the tunneling behavior between the channel and FG is controlled by three kinds of current-limiting paths, i.e., tunneling barrier, 2D/metal contact, and pn junction in the channel. Based on the understanding of the memory operation mechanism through the V FG trajectory measurement, we propose the best all 2D NVM device structure with a direct tunneling path between source/drain electrodes and floating gate for ultrafast memory operation. Indeed, a 50 ns program/erase operation is successfully achieved [3]. Moreover, we examined the dielectric breakdown strength (E BD) of h-BN under short voltage pulses for the origin for this ultrafast operation, because a high dielectric breakdown strength allows a large tunneling current. Surprisingly, an E BD = 26.1 MV/cm for h-BN is realized under short voltage pulses, largely exceeding the E BD = ~12 MV/cm from the DC measurement. This suggests that the high E BD of h-BN can be the physical origin of the ultrafast operations. In this talk, I would like to discuss the future perspective of 2D NVM application.[1] T. Sasaki, KN, et al., "Understanding the Memory Window Overestimation of 2D Materials Based Floating Gate Type Memory Devices by Measuring Floating Gate Voltage", Small, 2020, 16, 2004907.[2] T. Sasaki, KN, et al., "Material and Device Structure Designs for 2D Memory Devices Based on the Floating Gate Voltage Trajectory", ACS nano, 2021, 15, 6658.[3] T. Sasaki, KN, et al., "Ultrafast Operation of All 2D-Heterostructured Nonvolatile Memory Devices Provided by the Strong Short-Time Dielectric Breakdown Strength of h-BN", Adv. Funct. Mater. (under revision).

Stable Resistive Switching in ZnO/PVA:MoS2 Bilayer Memristor.

Reliability of nonvolatile resistive switching devices is the key point for practical applications of next-generation nonvolatile memories. Nowadays, nanostructured organic/inorganic heterojunction composites have gained wide attention due to their application potential in terms of large scalability and low-cost fabrication technique. In this study, the interaction between polyvinyl alcohol (PVA) and two-dimensional material molybdenum disulfide (MoS2) with different mixing ratios was investigated. The result confirms that the optimal ratio of PVA:MoS2 is 4:1, which presents an excellent resistive switching behavior. Moreover, we propose a resistive switching model of Ag/ZnO/PVA:MoS2/ITO bilayer structure, which inserts the ZnO as the protective layer between the electrode and the composite film. Compared with the device without ZnO layer structure, the resistive switching performance of Ag/ZnO/PVA:MoS2/ITO was improved greatly. Furthermore, a large resistive memory window up to 104 was observed in the Ag/ZnO/PVA:MoS2/ITO device, which enhanced at least three orders of magnitude more than the Ag/PVA:MoS2/ITO device. The proposed nanostructured Ag/ZnO/PVA:MoS2/ITO device has shown great application potential for the nonvolatile multilevel data storage memory.

Epitaxial growth and phase evolution of ferroelectric La-doped HfO2 films

Hafnium-oxide-based materials are considered a promising candidate for next-generation nonvolatile memory devices owing to their good CMOS compatibility and robust ferroelectricity at the nanoscale. In this work, we synthesize highly (111)-oriented La-doped HfO2 (HLO) ferroelectric thin films via pulsed laser deposition. Furthermore, the effect of La dopant concentration, thickness, and growth temperature on the ferroelectricity of HLO films is investigated in detail. A maximum remnant polarization of ∼9 μC/cm2 is achieved for only the 5-nm-thick 3 mol. % HLO films without a wake-up process. The 180° inversion of the domain, the butterfly-shaped capacitance–voltage curve, and typical ferroelectric displacement current curve further demonstrate the robust ferroelectricity at the nanoscale. Moreover, the phase evolves from the monoclinic to the orthorhombic and subsequently to the cubic phase with increasing La concentration, which is due to the combined action of oxygen vacancy, epitaxial strain, and chemical pressure. Additionally, in the interface configuration of HLO/La0.7Sr0.3MnO3 (LSMO), the MnO20.7− layer is substituted by the HLO layer on the MnO2-terminated surface of LSMO, which can be attributed to the fact that the HLO layer with higher electronegativity replaces the MnO20.7− layer with the same electronegativity in the HLO film. Therefore, this study provides a reliable pathway for directly obtaining a lightly doped HLO ferroelectric thin film, which can help to broaden the understanding of the ferroelectric physical mechanisms with element doping.

Conduction mechanisms of ferroelectric La:HfO2 ultrathin films

Recently, ion-doped HfO2 thin films are highly desirable for the next-generation nonvolatile memories due to excellent compatibility with current complementary metal-oxide-semiconductor processes and robust ferroelectricity persisted down to the nanoscale. In this work, we study conduction mechanisms of 4 and 8 nm-thick La:HfO2 ultrathin films sandwiched between Pt and (La0.67,Sr0.33)MnO3 (LSMO) electrodes based on band alignments of the Pt/La:HfO2/LSMO, measured by x-ray photoelectron spectroscopy, and temperature-dependent current-voltage curves from 50 to 300 K. In a 4 nm-thick La:HfO2 thin-film capacitor, the conduction mechanism is found to be governed by direct tunneling at 50–100 K and phonon-assisted indirect tunneling when the temperature is further increased to 300 K in which the (LaHf4+3+)′ acceptors are served as localized states, facilitating hole hopping through the La:HfO2 barrier. When the thickness is increased to 8 nm, the tunneling through a La:HfO2 layer is suppressed, and the current-voltage character becomes rectifying, which is regulated by the dominated La:HfO2/LSMO interfacial barrier. The transport for a forward bias of the La:HfO2/LSMO barrier is found to be governed by thermionic-field emission, exhibiting a temperature-independent build-in potential of ∼2.77 V. For the reverse bias, the Fowler–Nordheim tunneling is observed. The revealing of conduction mechanisms in terms of band alignments sheds light on leakage problems and facilitates the design of HfO2-based ferroelectric devices with excellent insulating character for high-performance memory applications.

Improved analog switching characteristics of Ta2O5-based memristor using indium tin oxide buffer layer for neuromorphic computing

A memristor is defined as a non-volatile memory switching two-terminal resistor, and a memristor with digital switching characteristics is widely studied as a next-generation non-volatile memory because of its simple structure, high integration density, and low power consumption. Recently, analog memristors with gradual resistance switching (RS) characteristics have garnered great attention because of their potential to implement artificial synapses that can emulate the brain functions. Transition metal oxides are thought to be strong candidate materials for the RS. In particular, tantalum oxide (TaO x )-based memristive devices provide stable and durable switching characteristics. TaO x -based memristors utilize analog switching characteristics and have excellent durability and reliability, so they can be applied as artificial synaptic device. In this study, the characteristics of analog RS using Ta2O5-based memristive devices were investigated. The current level of the Pt/Ta2O5/Pt memristors was improved by adjusting the thickness of Ta2O5. In particular, when an indium-tin-oxide (ITO) buffer layer was added to Ta2O5 forming a Pt/ITO/Ta2O5/Pt heterostructured double-layer device, it showed more symmetrical potentiation and depression characteristics under both polarities than a single-layer device without ITO layer. The symmetrical and linear potentiation and depression characteristics are essential for the development of efficient memristor-based neuromorphic systems. Insertion of the ITO buffer layer improves linearity, symmetry, and stability of the analog RS properties of Ta2O5-based memristors to artificial synapses.

Enhancing the Resistive Switching Performance in a Physically Transient Memristor by Doping MoS2 Quantum Dots

Resistive random-access memory has attracted tremendous attention and numerous investigations as a promising next-generation nonvolatile memory device to address the physical limits of flash memory. Particularly, physically transient resistive switching memory is intensively researched for its degradable and environmentally friendly characteristics. Zinc oxide ($\mathrm{Zn}\mathrm{O}$), as a low-cost biocompatible and biodegradable material, has been widely used in the dielectric layer, yet many previous studies on $\mathrm{Zn}\mathrm{O}$-based memory devices show unsatisfactory switching properties. In this work, ${\mathrm{Mo}\mathrm{S}}_{2}$ quantum dots (QDs) are added between the $\mathrm{W}$ bottom electrode and $\mathrm{Zn}\mathrm{O}$ insulator by spin coating ($\mathrm{W}/{\mathrm{Mo}\mathrm{S}}_{2}$ QD$/\mathrm{Zn}\mathrm{O}/\mathrm{Ag}$) to improve its resistive switching behavior. The modified device exhibits distinctly better properties, including more-uniform switching parameters (low- and high-resistance states, ${V}_{\mathrm{set}}$, ${V}_{\mathrm{reset}}$), ultralow threshold voltages, and steady retention. Moreover, we transfer the device onto polyvinyl alcohol substrate, making it fully degradable, and it is completely dissolved in phosphate-buffered solution after 40 min. These results indicate that the ${\mathrm{Mo}\mathrm{S}}_{2}$ QD--optimized transient resistive switching memory shows great potential in green electronics, implantable biomedical devices, and secure information-storage applications.

CMOS-compatible wafer-scale Si subulate array for superb switching uniformity of RRAM with localized nanofilaments

Resistive switching random access memory (RRAM) is one of the most promising candidates with high-density three-dimensional integration characteristics for next-generation nonvolatile memory technology. However, the poor uniformity issue caused by the stochastic property of the conductive filament (CF) impedes the large-scale manufacture of RRAM chips. Subulate array has been introduced into the RRAM to minimize the CF randomness, but the methods are cumbersome, expensive, or resolution-limited for large-scale preparation. In this work, Si subulate array (SSA) substrates with different curvature radii prepared by a wafer-scale and nanoscale-controllable method are introduced for RRAM fabrication. The SSA structure, which induces a quasi-single CF or a few CFs formed in the tip region (TR) of the device as evidenced by the high-resolution transmission electron microscopy and energy dispersive spectroscopy characterization, dramatically improves the cycle-to-cycle and device-to-device uniformity. Decreasing the curvature radius of the TR significantly improves the device performance, including switching voltages, high/low resistance states, and retention characteristics. The improved uniformity can be attributed to the enhanced local electric field in the TR. The proposed SSA provides a low-cost, uniform, CMOS-compatible, and nanoscale-controllable optimization strategy for the large-scale integration of highly uniform RRAM devices.

Impact of Thermal Boundary Resistance on Thermoelectric Effects of the Blade-Type Phase-Change Random Access Memory Device

Phase-change random access memory (PCRAM) is widely regarded as one of the most promising candidates to replace Flash memory as the next generation of non-volatile memories due to its high-speed and low-power consumption characteristics. Recent advent of the blade-type PCRAM with low programming current merit further confirms its prospects. The thermoelectric effects existing inside the PCRAM devices have always been an important factor that determines the phase-transformation kinetics due to a fact that it allows PCRAM to have electric polarity dependent characteristics. However, the potential physics governing the thermoelectric effects for blade-type PCRAM device still remains vague. We establish a three-dimensional (3D) electro-thermal and phase-transformation model to study the influences of thermal boundary resistance (TBR) and device scaling on the thermoelectric effects of the blade-type PCRAM during its “RESET” operation. Our research shows that the presence of TBR significantly improves the electric polarity-dependent characteristics of the blade-type PCRAM, and such polarity-dependent characteristic is found immune to the scaling of the device. It is therefore possible to optimize the thermoelectric effects of the blade-type PCRAM through appropriately tailoring the TBR parameters, thus further lowering resulting power consumption.

Hybrid Spintronics/CMOS Logic Circuits Using All-Optical-Enabled Magnetic Tunnel Junction

Spintronics is one of the emerging fields for next-generation low power, high endurance, non-volatile, and area efficient memory technology. Spin torque transfer (STT), spin orbit torque (SOT), and electric field assisted switching mechanisms have been used to switch magnetization in various spintronic devices. However, their operation speed is fundamentally limited by the spin precession time that typically ranges in 10–400 ps. Such a time constraint severely limits the possible operation of these devices in high-speed systems. Optical switching using ultrashort laser pulses, on the other hand, is able to achieve sub-picosecond switching operation in magnetic tunnel junctions (MTJs). In this paper, all optically switched (AOS) MTJ has been used to design high speed and low power hybrid MTJ/CMOS based logic circuits such as AND/NAND, XOR/XNOR, and full adder. Owing to the ultra-fast switching operation of AOS-MTJ, the circuit level results show that the energy and speed of AOS-MTJ based logic circuits are improved by 85% and 97%, respectively, when compared to STT based circuits. In comparison to SOT based designs, the proposed logic circuits show 10% and 91% improvement in energy efficiency and speed, respectively.

Solution-processed light-induced multilevel non-volatile wearable memory device based on CsPb2Br5 perovskite.

Despite the recent advancements in memory devices, the quest for building materials with low power consumption is still on, with the ultimate focus on the durability of the system and reliability and reproducibility of its performance. Halide perovskites (HPs), which have several intriguing photoelectrical traits, have recently been utilized for memory applications; one of the highlights of these materials is the ionic-motion-based fast switching in their crystal structure. In this work, a CsPb2Br5 film is applied as a switching layer to implement memory devices with a flexible Al/CsPb2Br5/ITO-PET structure. The device exhibits a pronounced bipolar resistive switching (RS) characteristic at low operating voltage. The as-fabricated flexible device presented RS features with no initial forming process, concentrated distributions of high and low resistance states (HRS and LRS), uniform switching, endurance over 100 cycles, and a long retention time of 103 s with a high on/off ratio of around 102. Multilevel data-storage capability was also observed via subtle control of the compliance current (CC). Considering the current demand for smart, wearable, and flexible electronic gadgets, the current-voltage (I-V) characteristics of the as-fabricated all-inorganic halide-perovskite-based memory device were further explored under different bending conditions to determine its electrical reliability and mechanical stability. This flexible device exhibited no discernible difference in device performance under flat or bent conditions, and the performance remained nearly the same even after 500 bending cycles. In addition to control of the RS effect of the device using an electrical field, the performance of the device under light was also explored. Blue light modulates the resistive states by regulating the condition of photo-generated electron-hole pairs, and the SET and RESET voltages are changed from 2.34 to 2.14 V and from -2.04 to -1.90 V, respectively. The observed RS behavior is explained on the basis of the creation and partial annihilation of conductive multifilaments, which is dominated by the migration of bromine ions and their associated vacancies in the HP layer. We believe that this work will offer a new context to understand the intrinsic characteristics of HPs for RS applications at low voltage and validate their potential in the design of next-generation stable and nonvolatile memory devices for future flexible electronic systems.

Nano-analytical investigation of the forming process in an HfO2-based resistive switching memory

Metal oxide-based resistive random access memory devices are highly attractive candidates for next-generation nonvolatile memories, but the resistive switching phenomena remain poorly understood. This article focuses on the microscopic understanding of the initial forming step, which is decisive for the switching process. The integrated resistive switching memory effect in Ti/HfO2/TiWN metal insulator metal structures is studied. After forming, transmission electron microscopy investigations pointed out the presence of a funnel-shaped region, in the ON state of the cell, where slightly oxidized Ti (TiOx) was present within HfO2 dielectric. Modeling of the measured ON state conductance of the cell with the semi-classical approximation is consistent with a conductive nanometric TiOx filament (or a sum of sub-nanometric TiOx filaments) present in the funnel-shaped region. The conductive area is likely formed by diffusion after the dielectric breakdown.

High-Speed Switching and Giant Electroresistance in an Epitaxial Hf0.5Zr0.5O2-Based Ferroelectric Tunnel Junction Memristor

HfO2-based ferroelectric materials are good candidates for constructing next-generation nonvolatile memories and high-performance electronic synapses and have attracted extensive attention from both academia and industry. Here, a Hf0.5Zr0.5O2-based ferroelectric tunnel junction (FTJ) memristor is successfully fabricated by epitaxially growing a Hf0.5Zr0.5O2 film on a 0.7 wt % Nb-doped SrTiO3 (001) substrate with a buffer layer of La2/3Sr1/3MnO3 (∼1 u.c.). The FTJ shows a high switching speed of 20 ns, a giant electroresistance ratio of ∼834, and multiple states (eight states or three bits) with good retention >104 s. As a solid synaptic device, tunable synapse functions have also been obtained, including long-term potentiation, long-term depression, and spike-timing-dependent plasticity. These results highlight the promising applications of Hf0.5Zr0.5O2-based FTJ in ultrafast-speed and high-density nonvolatile memories and artificial synapses.

Single Crystal Halide Perovskite Film for Nonlinear Resistive Memory with Ultrahigh Switching Ratio.

Morre's law is coming to an end only if the memory industry can keep stuffing the devices with new functionality. Halide perovskite acts as a promising candidate for application in next-generation nonvolatile memory. As is well known, the switching ratio is the key device requirement of resistive memory to improve recognition accuracy. Here, the authors introduce an all-inorganic halide perovskite CsPbBr3 single crystal film (SCF) into resistive memory as an active layer. The Ag/CsPbBr3 /Ag memory cells exhibit reproducible resistive switching with an ultrahigh switching ratio (over 109 ) and a fast switching speed (1.8µs). It is studied that the Schottky barrier of metal/CsPbBr3 SCF contact follows the tendency of Schottky-Mott theory, and the Fermi level pinning effect is effectively reduced. The interface S parameter of metal/CsPbBr3 SCF contact is 0.50, suggesting a great interface contact is formed. The great interface contact contributes to the steady high resistance state (HRS), and then the steady HRS leads to an ultrahigh resistive switching ratio. This work demonstrates high performance from halide perovskite SCF-based memory. The introduction of halide perovskite SCF in resistive random access memory provides great potential as an alternative in future computing systems.

Nanoscale Multiferroic Properties at Room Temperature of Lead Zirconate Titanate Iron Tantalate for Memory Device Applications

The evolution of device miniaturization and the potential application for next-generation nonvolatile memory devices Pb(Zr0.53Ti0.47)0.60(Fe0.5Ta0.5)0.40O3 (PZTFT) can be used as a barrier in multiferroic tunnel junctions. We report single-phase magnetoelectric multiferroic ultra-thin PZTFT at room temperature. The magnetic and ferroelectric properties have been investigated down to 7 nm thickness which are requisite properties for multiferroic tunnel barriers for multi-states memory applications. In the present study, we show that it remains a switching multiferroic at room temperature down to at least thickness d = 7 nm, which is thin enough for tunnel junctions.

Rational Design on Controllable Cation Injection with Improved Conductive-Bridge Random Access Memory by Glancing Angle Deposition Technology toward Neuromorphic Application.

A conductive-bridge random access memory (CBRAM) has been considered a promising candidate for the next-generation nonvolatile memory technology because of its excellent performance, for which the resistive switching behavior depends on the formation/dissolution of conducting filaments in an electrolyte layer originated by the cation injection from the active electrode with electrochemical reactions. Typically, the controllability of cations into the electrolyte layer is a main issue, leading to stable switching reliability. In this work, an architecture combining spike-shaped Ag electrodes created by Al2O3 nanopillar arrays as a physical diffusion barrier by glancing angle deposition technology was proposed to localize Ag cation injection for the formation of controllable filaments inside TiOx as the switching layer. Interestingly, the dimension of the Ag plugs defined by the topography of Al2O3 nanopillar arrays can control Ag cation injection to influence the dimensionality of conductive filaments. Compared to the typical planar-Ag/TiOx/Pt device, the spiked-Ag/Al2O3 nanopillar arrays/TiOx/Pt device shows improvement of endurance and voltage disturbance. With enhanced multilevel characteristics, the spiked active-metal-based CBRAM device can be expected to serve as an analogue synapse for neuromorphic applications.

Grain boundary effect on the resistive switching characteristics of SrTi1-xFexO3 directly patterned via photochemical organic-metal deposition

Ionic memristors are a promising candidate for use in next-generation non-volatile memory and neuromorphic computing systems. To ensure that ionic memristors exhibit appropriate resistive switching characteristics, the precise control of oxygen vacancies is required. The ABO3 structure can accommodate various ions of different sizes in the A and B sites, and this flexibility allows for the accurate design of materials and for the oxygen defects to be controlled. This study systematically investigated the effect of Fe doping on the resistive switching characteristics of SrTi1-xFexO3 (x = 0, 0.05, 0.10, and 0.15) films fabricated using photochemical organic–metal deposition. The Fe dopant created oxygen vacancies via Schottky defects, especially at grain boundaries, with the space charge at the grain boundaries inhibiting grain growth and increased the number of defective grain boundaries. Since the defective grain boundary acts as a conducting path filament, an increase in the Fe content reduced the initial resistance of the films, and SrTi1-xFexO3 film optimized Fe content exhibited complementary resistive switching behavior without the need for a forming process. The Fe doping effects on the crystal and electronic structure were also analyzed using X-ray diffraction, valence band, O 1s X-ray absorption, and Raman spectra.

Observation of nonvolatile resistive switching behaviors in 2D layered InSe nanosheets through controllable oxidation

Scientists have been seeking for suitable materials with nonvolatile resistive switching (RS) performance for memristive applications. Recently, nonvolatile RS behaviors have been achieved in an increasing number of two-dimensional (2D) materials. However, 2D InSe layers have not been reported to demonstrate such nonvolatile RS behaviors. Herein, we experimentally observe nonvolatile bipolar RS behaviors in 2D InSe nanosheets through controllable oxidation. In our experiments, the exfoliated InSe nanosheets annealed at the temperature of 350 °C for 2 h show typical nonvolatile bipolar RS performance with a low SET voltage of ∼0.3 V and a high ON/OFF ratio of 4.5 × 103 at the read voltage of 0.1 V. Raman and x-ray photoelectron spectroscopy characterizations confirm the partial oxidation in InSe nanosheets after annealing. The observed nonvolatile RS behaviors are owing to the formation of In2O3 and the increased insulating characteristic in the annealed InSe nanosheets. Furthermore, the fabricated memristor exhibits good retention property and endurance performance. Such annealed InSe nanosheets not only demonstrate decent RS performance but also enrich the family of 2D materials to fabricate memristors for applications in next-generation nonvolatile memory.

Memristive devices based on mass printed organic resistive switching layers

Resistive random-access memory is a candidate for next-generation non-volatile memory architectures. In this study, we use flexographic roll-to-roll printing technology for deposition of the resistive layer, a printing method that allows fast and cost-effective fabrication to create non-volatile resistive memory devices. Metal-free organic polymers blends composed of poly(methyl methacrylate) (PMMA) and a surplus of poly(vinyl alcohol) (PVA) serve as the active layer. Microscopic studies of the roll-to-roll printed layers show circular domains of PMMA embedded in PVA. The influence of the PMMA content in the polymer blend is investigated with respect to the performance and reliability of the resistive memory cells. Electrical characterization reveals a retention time of at least eleven days, a Roff/Ron ratio of approx. two orders and write/erase voltages of + 1/−2 V.

Observation of ultrafast amorphization dynamics in GeCu2Te3 thin films using echelon-based single-shot transient absorbance spectroscopy

The compound GeCu2Te3 (GCT) has attracted considerable attention because of its several advantages for next-generation nonvolatile memories, including its higher thermal stability and lower volume change, with large optical contrast between the crystalline and amorphous phases. In this study, we demonstrate the ultrafast amorphization dynamics that occur in GCT by utilizing echelon-based single-shot transient absorbance spectroscopy and coherent phonon spectroscopy. We find that the timescale of the absorbance change accompanying amorphization is ∼2 ps, which is close to the dephasing time of the A1 optical phonons. Based on the observed results and the robust structural network of crystalline GCT, we discuss the amorphization dynamics in GCT by comparing it with that in the typical phase-change material Ge2Sb2Te5.

Resistive Switching Effect of Multiferroic Complex Oxide Solid Solution Thin Films

Resistive switching in multiferroics has attracted increasing attention due to the potential application for next-generation nonvolatile memory and could lead to forms of computing. However, the resistive switching mechanism in solid solution oxides is unclear. In this article, we have successfully fabricated binary 0.72BiTi0.27Fe0.46Mg0.27O3-0.28LaFeO3 (BTFM-LFO) and ternary 0.625BiTi0.27Fe0.46Mg0.27O3-0.25LaFeO3-0.125La2MgTiO6 (BTFM-LFO-LMT) thin films with precise component control by the spin coating method. The solid solution films exhibit obvious ferroelectricity and magnetism at room temperature. Both binary and ternary solid solution films show switchable polarization, weak magnetism, and reversible and repeatable resistive switching effects. Multistage resistive switching behavior was observed. Four resistive switching states were obtained in the binary film; the highest Ion/off is up to 106. The influence of the film composition on the resistive switching effect was discussed. It is considered that the oxide vacancy/valance exchange-induced defects play a dominant role in the resistive switching effect of complex oxide thin films. This work provides an alternative pathway to explore the resistive switching in multiferroic oxides by fabrication of complex solid solution films.