Bipolar Resistive Switching Research Articles

Ferroelectric Resistance Switching in Epitaxial BiFeO3/La0.7Sr0.3MnO3 Heterostructures.

BiFeO3/La0.7Sr0.3MnO3 (BFO/LSMO) epitaxial heterostructures were successfully synthesized by pulsed laser deposition on (001)-oriented SrTiO3 single-crystal substrates with Au top electrodes. Stable bipolar resistive switching characteristics regulated by ferroelectric polarization reversal was observed in the Au/BFO/LSMO heterostructures. The conduction mechanism was revealed to follow the Schottky emission model, and the Schottky barriers in high-resistance and low-resistance states were estimated based on temperature-dependent current-voltage curves. Further, the observed memristive behavior was interpreted via the modulation effect on the depletion region width and the Schottky barrier height caused by ferroelectric polarization reversal, combining with the oxygen vacancies migration near the BFO/LSMO interface.

Uniform multilevel switching and synaptic properties in RF-sputtered InGaZnO-based memristor treated with oxygen plasma.

Bipolar gradual resistive switching was investigated in ITO/InGaZnO/ITO resistive switching devices. Controlled intrinsic oxygen vacancy formation inside the switching layer enabled the establishment of a stable multilevel memory state, allowing for RESET voltage control and non-degradable data endurance. The ITO/InGaZnO interface governs the migration of oxygen ions and redox reactions within the switching layer. Voltage-stress-induced electron trapping and oxygen vacancy formation were observed before conductive filament electroforming. This device mimicked biological synapses, demonstrating short- and long-term potentiation and depression through electrical pulse sequences. Modulation of post-synaptic currents and pulse frequency-dependent short-term potentiation were successfully emulated in the InGaZnO-based artificial synapse. The ITO/InGaZnO/ITO memristor exhibited spike-amplitude-dependent plasticity, spike-rate-dependent plasticity, and potentiation-depression synaptic learning with low energy consumption, making it a promising candidate for large-scale integration.

Study of electrical transport and high voltage resistive switching on Ag/PVDF-fibres/Ag and Ag/PVDF-pellet/Ag for memory applications

In this letter, the resistive switching effects of one-dimensional PVDF in a geometry of Ag/ PVDF fibers/Ag and Ag/fibers’ pellet/Ag have been explored. Electrospinning has been utilized to fabricate PVDF fibers with the solution of Dimethyl Formamide (DMF)/Acetone (4:6) in the weight percentage of 12 wt% using the Far Field Electrospinnur method. Structure and microstructure are evaluated with Confocal Raman spectroscopy, X-ray diffraction Spectrometer, and Bruker MM8 Atomic Force Microscopy (AFM). A bipolar resistive switching with set voltage from 24 to 25 V, reset voltage from −12 to −15 V, and set voltage 26.5 to 30 V, reset voltage −28 to −15 V are observed for fibers and pellet respectively. Pellet has shown trap-filled space charge limited current (TSCLC) behavior, fibers show resistive switching, Ohmic, free and filled trap SCLC behavior, and obeys with Mott-Gurney's trapped SCLC model.

Symmetric bipolar resistive switching in copper oxide nanostructure/ITO lateral device under exposure to atmospheric oxygen and application in artificial synaptic devices

Capacitively coupled resistive switching behaviour was observed in a planar-geometry two-terminal device based on nanostructures of copper oxide as active material and indium tin oxide (ITO) as electrodes. When tested in ambient atmosphere, current-voltage I−V characteristic was found to be symmetric with pronounced hysteresis loop signifying two different states of resistance, namely the low resistive state (LRS) and high resistive state (HRS). Capacitive effect was apparent in the low voltage regime due to the presence of offset voltage at zero current and offset current at zero bias. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of native oxygen vacancies in copper oxide. Additionally, exposure to atmospheric oxygen played the dominant role in creation of excess vacancy sites by electrochemical reaction near positive electrode. Creation of excess density of oxygen vacancy near the electrodes in conjunction with trapping and detrapping of electrons from these defect sites is perceived as the prime mechanism for the observed switching behaviour. The device ON/OFF ratio, ION/IOFF∼1.5 was found to be stable over at least 100 continuous cycles. When tested under vacuum, the device I−V characteristics was linear in shape without any hysteresis signifying ohmic transport. Analysis of ultraviolet photoelectron spectroscopy (UPS) showed the Fermi energy level of copper oxide is at ∼ 4.69 eV, which is in a close match with the work function of ITO-electrode. The essential synaptic characteristics such as learning and forgetting curves and paired pulse facilitation (PPF) are established. The nonlinearity factors (NLF) are very low indicating the copper oxide-based devices are promising candidates for neuromorphic applications.

Bipolar resistive switching behavior and endurance in RF-sputtered bilayer HfO2/ZrO2 resistive random access memory

Bipolar resistive switching behavior and endurance in RF-sputtered bilayer HfO2/ZrO2 resistive random access memory

Implementation of Stable Nonvolatile Resistive Switching Behaviors in TiO2 Nanoparticle‐Incorporated 2D Layered Halide Perovskite‐Based Devices

2D organic–inorganic layered halide perovskites have received tremendous interest as promising materials in electronics owing to their outstanding physical properties. However, the quantum confinement effect leads to the suppression of ion migration in the out‐of‐plane direction, restricting their applications in resistive switching (RS) memories with vertical structure. Herein, the 2D layered perovskite incorporated with TiO2 nanoparticles, denoted as TiO2–PEA2PbBr4, is employed, as the functional layers to construct RS memory devices with Al/TiO2–PEA2PbBr4/ITO structure. As compared to pure 2D layered perovskite counterparts without switching behaviors, the Al/TiO2–PEA2PbBr4/ITO memories demonstrate stable bipolar RS behaviors, along with striking characteristics, including the relatively centralized set/reset voltages, a large on/off ratio (≈102), and a long retention time (104 s). In addition, the devices also present the multilevel storage capability by controlling the compliance current. Moreover, the RS behaviors are attributable to the formation/rupture of synergy bromine and oxygen vacancy conductive filaments, owing to their migration/distribution of oxygen/bromine ions under electric fields. The oxide nanoparticles incorporation route provides an effective strategy for improving RS performance in 2D layered perovskite‐based RS memories.

Effects of rubidium substitution of Cs2−xRbxAgBiBr6 double halide perovskites on resistive switching characteristics for memory applications

Cation substitution technique in halide perovskites (HPs) is one of the famous schemes to enhance the characteristics of HPs-based electronic and optoelectronic devices. Here, we fabricated rubidium (Rb) substituted inorganic double halide perovskites (HPs) Cs2−xRbxAgBiBr6 (x = 0, 0.05, 0.1, 0.2, and 0.3) film-based resistive switching (RS) devices and investigated effects of Rb cation substitution on characteristics of RS devices. Grain sizes of the formed Cs2−xRbxAgBiBr6 films gradually increased as increase of Rb contents in the precursor. All of the fabricated RS devices demonstrated non-volatile bipolar RS behavior, device with the Rb content x = 0.1 showed a particularly high on/off ratio (9.29 × 102) of about 30 times greater than pristine Cs2AgBiBr6-based ones (3.09 × 10). In addition, it has been shown that an appropriate amount of Rb substitution at the level of x = 0.1 can effectively prevent the appearance of other crystalline phases at high humidity condition of > 80 %. Through various analytical techniques including SEM, XPS, and SCLC measurement, it was confirmed that an enlargement in grain size resulting in a decrease in defects such as Br vacancies in the fabricated film can lead to an increase in resistance at a high resistance state (HRS) and high on/off resistance ratio. This study provides a facile and feasible way to enhance performances of HPs-based RS devices for practical electronic memory applications.

Resistive switching behaviour of nickel nanoparticle-embedded naphthalene sulphonic acid-doped polyaniline nanocomposites

Hybrid nanocomposite (NC) materials comprising organic polymers and inorganic metal nanoparticles (NPs) with unique properties are popular for their advanced technological applications including resistive switching memory devices. Herein, NCs of 2-naphthalene sulphonic acid-doped polyaniline nanotubes (PANI-NSA NTs) and nickel nanoparticles (Ni NPs) were synthesized via a facile chemical synthesis procedure where metallic Ni NPs were embedded in/deposited onto the surface of PANI-NSA NTs by a simple reduction method. Different characterization methods revealed successful deposition of weak ferromagnetic Ni NPs onto the PANI-NSA matrix. The bipolar resistive switching behaviour of the as-synthesized PANI-NSA + Ni NCs was investigated under the application of voltage stress in a two-terminal sandwiched device configuration. The fabricated indium tin oxide/PANI-NSA + Ni/silver (ITO/PANI-NSA + Ni/Ag) device displays bipolar resistive switching properties having a memory window of ∼1.5 × 103, and switches effectively over 200 cycles. Ohmic conduction in the lower-voltage regime and the space-charge-limited Mott–Gurney current conduction model in the higher-voltage region were identified as major charge conduction mechanisms in the high resistive state of the device. On the other hand, in the entire low resistive state region the experimental data followed the Mott–Gurney conduction model.

NiFe2O4 nanoparticles for non-volatile bipolar resistive switching memory device

The present work reports the chemical synthesis of NiFe2O4 (NFO) nanoparticles (NPs) and its use as a switching layer material in resistive switching (RS) devices. Various analytical techniques were used to confirm the phase, composition, and optical properties of the NFO NPs. With the support of the x-ray diffraction technique, crystal structure (cubic spinel) and crystallite size (20.12 nm) were determined. Field emission scanning electron microscopy confirmed the material morphology. Raman Spectroscopy and Fourier Transform Infrared Spectroscopy were applied to identify the NFO NPs functional groups. The Ag/NFO/fluorine-doped tin oxide device was fabricated, which shows bipolar RS with good endurance (104cycles) and retention (6 × 103 s) properties. Moreover, the device’s conduction and RS mechanisms were also carried out.

Controllable analog-to-digital bipolar resistive switching behavior and mechanism analysis in δ-MnO2-based memristor

Memristor is one of the most emerging electronic components to realize synaptic functions in the neuromorphic computing. Memristor with controllable analog-to-digital resistive switching behaviors has the potential to considerably accelerate the realization of high-performance neuromorphic computing. In this work, a memristor with Ag/δ-MnO2/Ti structure was fabricated, and an analog-to-digital resistive switching behavior with voltage regulation was demonstrated. Memristive switching with analogue characteristics can generate a gradual increase in conductance at low voltage of less than 1.3 V to aid in the building of artificial synapses. The Ag/δ-MnO2/Ti memristor with excellent digital resistive switching performance can be applied for data storage and in-memory computation at voltage windows of higher than 1.3 V. Furthermore, the resistive switching mechanism was analyzed by employing the first-principle calculation. The main reason for the emergence of digital memristor characteristics is the Ag+ ions can enter to the δ-MnO2 layer driven by a larger voltage and continue to cluster and form conductive filament. This work enriches the application of analog-to-digital bipolar memristor in neuromorphic computing, and facilitates further realization of memristor in low-power and high-density circuit integration.

Resistive switching characteristics of MnO2-based thin film for transparent non-volatile ReRAM

The present study covers the fabrication of indium tin oxide (ITO)/manganese dioxide (MnO2)/ITO capacitor-based transparent resistive random access memory (ReRAM) device. The ITO/MnO2/ITO device exhibits 80 % transparency in the visible region along with steady bipolar resistive switching characteristics. The conduction mechanism investigation reveals that the current in low resistance state (LRS) is governed by Ohmic conduction. However, the dominance of trap-controlled space charge limited conduction (SCLC) mechanism in high resistance state (HRS) was observed. The resistive switching phenomenon in ITO/MnO2/ITO device was caused due to the formation and rupture of conduction filament via electron trapping and de-trapping in oxide-related traps (oxygen vacancies). In terms of reliability, the MnO2-based device exhibits good endurance up to 104 cycles and long retention for 104 s at room-temperature as well as at 85 °C. Cumulative probability distribution shows resistance ratio of 103 between LRS and HRS, which is sufficient to read memory states. These outcomes suggest that the ITO/MnO2/ITO-based transparent ReRAM could be a futuristic see-through electronic device for artificial intelligence (AI) application.

Analysis and Modeling of Bipolar Resistive Switching in 2-D Graphene Electrode- Based Memristor

Analysis and Modeling of Bipolar Resistive Switching in 2-D Graphene Electrode- Based Memristor

Co-existence of digital and analog resistive switching in 2D layered BiOI nanosheets for synaptic applications

The emulation of the biological synapses is essential for brain-inspired computing which is expected to overcome the traditional von Neumann bottleneck. Thus, synaptic memristor with analog resistive switching (RS) is highly desirable in non-volatile memristors for future neuromorphic computing. Herein, the co-existence of digital and analog RS can be observed in two-dimensional (2D) layered BiOI nanosheets sandwiched by the top and bottom Pt electrodes. The vertical Pt/BiOI/Pt memristors demonstrate typical bipolar RS behaviors with a large ON/OFF ratio of 1.0 × 103 and long retention time up to 1.6 × 104 s under a relatively large operation voltage. When the operation voltages are reduced to 1 V, analog RS behaviors with a series of tunable resistance states can be observed. The adjustable resistance states can be utilized to emulate “learning-forgetting” experience of human brain. Repeatable long-term potentiation (LTP) and long-term depression (LTD) cycles can be implemented based on the synaptic memristors, which can be used for simulation of artificial neural network for image recognition with accuracy up to 91.15 %. Moreover, Pavlov’s dog experiment is successfully emulated based on the synaptic memristors. This study suggests good prospects of the synaptic memristors based on BiOI nanosheets for future neuromorphic computing.

Double-Forming Mechanism of TaOx-Based Resistive Memory Device and Its Synaptic Applications.

The bipolar resistive switching properties of Pt/TaOx/InOx/ITO-resistive random-access memory devices under DC and pulse measurement conditions are explored in this work. Transmission electron microscopy and X-ray photoelectron spectroscopy were used to confirm the structure and chemical compositions of the devices. A unique two-step forming process referred to as the double-forming phenomenon and self-compliance characteristics are demonstrated under a DC sweep. A model based on oxygen vacancy migration is proposed to explain its conduction mechanism. Varying reset voltages and compliance currents were applied to evaluate multilevel cell characteristics. Furthermore, pulses were applied to the devices to demonstrate the neuromorphic system's application via testing potentiation, depression, spike-timing-dependent plasticity, and spike-rate-dependent plasticity.

Non-volatile resistive switching behavior and time series analysis of Ag/PVA-graphene oxide/Ag device

Non-volatile memory devices have been getting significant attention from researchers worldwide in recent years due to their application in resistive random access memory and neuromorphic computing. Here, we have fabricated polyvinyl alcohol-graphene oxide (PVA-GO) composite as an active material for the resistive switching with different concentrations of GO (0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 wt. % GO solution) dispersed in 5 wt. % PVA matrix in a 2:1 volume ratio. We demonstrate the non-volatile forming free resistive switching properties of Ag/PVA-GO/Ag devices. Structural properties of PVA-GO composites are established from the x-ray diffraction pattern, which indicates the complete dispersion of GO inside the PVA matrix. The Ag/PVA-GO-0.1 wt. %/Ag device shows better bipolar resistive switching at VSET ∼ 0.4 V and VRESET at ∼−0.8 V. This device indicates well-resolved two distinct states at a read voltage of 0.1 V in endurance and retention measurements. The fabricated device switches successfully tested for 2.5 × 103 cycles and retains its state for 3.36 × 103 s without any observable degradation. Furthermore, the non-volatile retention property was modeled using time series analysis. For this, Holt–Winter's exponential smoothing technique was utilized. Additionally, the charge–flux linkage characteristic shows the double-valued function, and time domain–charge and time domain–flux show asymmetric behaviors. The electrical conduction mechanism exhibits ohmic behavior in the entire region of the low resistance state and the lower voltage region of the high resistance state. In the high-voltage region of the high resistance state, the space charge-limited conduction mechanism is observed. The resistive switching behavior is explained with the help of an appropriate model.

Multi-level optical memory with logical operation modulated by surface barrier in a single CH3NH3PbI3 perovskite micro/nanowire device

CH3NH3PbI3 is a potential candidate for optical information storage because of its excellent photoelectric response and hysteresis effect. However, the interface mechanism of the CH3NH3PbI3-based memory is still controversial, and the precise control of the resistive switching effect requires an effective method. Here, single CH3NH3PbI3 micro/nanowire devices with symmetric Ag electrodes were constructed. The role of the reversible redox reaction on the Ag electrode to modulate the interfacial barrier has been proposed, and the hysteresis behavior of the device can be precisely controlled by adjusting the illumination intensity and bias polarity. For example, when strong light and high voltage are applied at the same time, the device exhibits a symmetrical negative differential resistance effect; after being subjected to strong light and high voltage, the device exhibits a bipolar resistive switching effect, and the polarity of the large voltage determines the I-V curve wrapping way. On this basis, the device obtains multi-level optical storage and logic operation functions. This work provides a new way to understand the synergistic memory effect of light and bias on halide perovskite, which is expected to be further applied in the integrated field of optical nonvolatile memory and logical.

Multilevel resistive switching memory in lead-free double perovskite La_{2}NiFeO_{6} films

Dense and flat La_{2}NiFeO_{6} (LNFO) films were fabricated on the indium tin oxide-coated glass (ITO/glass) substrate by sol–gel method. The bipolar resistive switching behavior (BRS) could be maintained in 100 cycles and remained after 30 days, indicating that the LNFO-based RS device owned good memory stability. Surprisingly, the multilevel RS characteristics were firstly observed in the Au/LNFO/ITO/glass device. The high resistance states (HRSs) and low resistance state (LRS) with the maximum ratio of sim 500 could be remained stably in 900 s and 130 cycles, demonstrating the fine retention and endurance ability of this LNFO-based RS device. The BRS behavior of Au/LNFO/ITO/glass devices primarily obeyed the SCLC mechanism controlled by oxygen vacancies (OVs) dispersed in the LNFO layer. Under the external electric field, injected electrons were captured or discharged by OVs during trapping or detrapping process in the LNFO layer. Thus, the resistive state switched between HRS and LRS reversibly. Moreover, the modulation of Schottky-like barrier formed at the Au/LNFO interface was contributed to the resistive states switchover. It was related to the change in OVs located at the dissipative region near the Au/LNFO interface. The multilevel RS ability of LNFO-based devices in this work provides an opportunity for researching deeply on the high density RS memory in lead-free double perovskite oxides-based devices.

Effects of stacking sequence and top electrode configuration on switching behaviors in ZnO-HfO2 hybrid resistive memories

The resistive switching (RS) behavior of multilayered ReRAM devices is typically influenced by two aspects: the intrinsic properties of the dielectric multilayer, and other extrinsic contributions. In this study, we deposited and investigated bi-layered memories incorporating ZnO and HfO2 dielectrics. Different stacking sequences of the two oxides (ZnO/HfO2 and HfO2/ZnO) were employed to explore the intrinsic contribution of the bilayer microstructure, while different top electrode configurations (Pt and Ti) were utilized to demonstrate the extrinsic impact. All devices exhibit characteristic bipolar RS behavior, showcasing their functionality. But interestingly, the device with a Pt top electrode displays digital RS behavior, while the one with a Ti top electrode exhibits analog RS behavior. The completely different switching types observed during the reset process of the ZnO-HfO2 hybrid resistive memories are attributed to different interface charge migration process and structural characteristic. And as compared to the tailoring effect of stacking sequences (bilayer microstructure and oxide/oxide interface), the tailoring effect of top electrode configuration (electrode materials and oxide/electrode interface) is much stronger. Based on the latter, the switching ratio can be remarkably improved by at least two orders of magnitude, the reset voltage (energy consumption) can also be significantly reduced, and other discussed switching parameters can also show greater improvement. The comprehensive comparative analysis of intrinsic and extrinsic contributions provides valuable insights for exploring the RS mechanism and optimizing the design of bi-layered memory devices.

Lead-free CsCu2Br3 perovskite for multilevel resistive switching memory

Organic–inorganic metal halide perovskites have recently attracted enormous interest in the field of resistive switching memories owing to their unique electrical properties. Unfortunately, two challenges, the inadequate long-term stability and the toxicity of lead, largely hinder their further practical application. Herein, a 1D all-inorganic lead-free CsCu2Br3 perovskite is proposed for resistive switching devices to resolve these issues. The CsCu2Br3-based resistive switching devices exhibit typical bipolar resistive switching behavior with low set voltage, high on/off ratio (103), stable retention properties (>2 × 104 s), and endurance (200 cycles) in air. The unencapsulated CsCu2Br3-based device still maintains resistive switching characteristics while stored in ambient environment for over 2 months. Moreover, four on-state multilevel information storage behavior has been observed by regulating the value of compliance current during set process. The resistive switching behavior is dominated by the formation and fracture of conductive filaments, which are induced by the movement of Br− ions under electrical bias. This work offers the opportunity and strategy for the design of air-stable and environment-friendly metal halide perovskite-based memory devices.

Two-dimensional growth of Cu-based materials with a nonvolatile resistive switching behavior

Two-dimensional (2D) crystals have attracted much attention to the application in next-generation non-volatile memories due to their interesting structures and features. Herein, we report the controllable synthesis of 2D Cu2SxSe1– x crystals via a facile ambient pressure vapor deposition method. And the planar and vertical devices on the synthesized Cu2SxSe1– x crystals demonstrate a stable nonvolatile resistance switching. Most importantly, the planar Cu2SxSe1–x devices show a bipolar resistance switching behavior with a memory window of ∼103 and a relatively low operating voltage (<1 V). While the vertical Cu2SxSe1–x device exhibits a unipolar switching behavior with a large memory window of ∼105. Our findings in this work broaden the horizon for the in-situ synthesis of 2D materials and enlighten the possibility of related applications in neural synapse and artificial intelligence.