Resistive Switching Effect Research Articles

Anomalous dielectric relaxation peak in Nb-doped SrTiO3 single crystals

Anomalous dielectric relaxation appears in Nb-doped SrTiO3 (SNT) single crystal with relaxation rate displaying unusual slowing down with increasing temperature. Dielectric measurements show that the resistivity increases with temperature. Raman spectrum and the spherical aberration-corrected transmission electron microscope (STEM) show the existence of polar nano regions (PNRs) in the crystal. The temperature-dependence of DC conductivity and current-voltage (I–V) curves suggest that this anomalous behavior happens at the interfaces of PNRs. The evolution of the anomalous relaxation peak in the annealed samples indicates that this effect is simultaneously affected by the carrier concentration and the interface structure. The anomalous dielectric relaxation is reminiscent of the positive temperature coefficient of resistance (PTCR) effect in a polycrystalline material. The resistive switching effect makes such materials to have potential application value in switches, sensors, and device miniaturization.

Unraveling the Effect of the Water Content in the Electrolyte on the Resistive Switching Properties of Self-Assembled One-Dimensional Anodized TiO2 Nanotubes.

The applied potential, time, and water content are crucial factors in the electrochemical anodization process because the growth of one-dimensional nanotubes can be accelerated by enhancing the corrosive effect. We investigated the effect of the water content on the resistive switching (RS) properties of Ti foils by anodizing the foils and varying the water content in an electrolyte (1-10 vol %). By increasing the water content, we facilitated a slow transition from nanopores to nanotubes and realized an increase in the tube wall diameter and tube length. All of the fabricated memristive devices exhibited a reliable and reproducible bipolar resistive switching effect. The optimized device exhibited bipolar RS properties with good dc endurance (104 cycles) and data retention capability (105 s). Our results suggest that as the water content increases to 5 vol %, the RS process improves; further increases in the water content impair the RS process.

Artificial optoelectronic synaptic characteristics of Bi2FeMnO6 ferroelectric memristor for neuromorphic computing

Photoelectric synapse is a new type of artificial synapse that combines light pulse excitation and electrical pulse excitation, and is an important component for the development of neuromorphic hardware. In this work, the Bi2FeMnO6 ferroelectric artificial synapse with optoelectronic response is reported. It can generate an excitatory post-synaptic current through ultraviolet light irradiation and then modulate the excitatory post-synaptic current through ferroelectric polarization, thereby realizing a photo-ferroelectric dual-control synapse. A training method based on ultraviolet excitation and ferroelectric enhancement is proposed, which greatly reduced the number of training pulses and increased the plasticity of the synapse. The optimized spike scheme based on ferroelectricity is proposed, which made the synapse have very linear weight adjustment function. This synapse is used to build a convolutional neural network, which can achieve 98.80% recognition accuracy on the MNIST dataset. In addition, the ferroelectricity and multi-level resistive switching effect of synapse have also been reported.

An Oxygen Vacancy Memristor Ruled by Electron Correlations.

Resistive switching effects offer new opportunities in the field of conventional memories as well as in the booming area of neuromorphic computing. Here the authors demonstrate memristive switching effects produced by a redox‐driven oxygen exchange in tunnel junctions based on NdNiO3, a strongly correlated electron system characterized by the presence of a metal‐to‐insulator transition (MIT). Strikingly, a strong interplay exists between the MIT and the redox mechanism, which on the one hand modifies the MIT itself, and on the other hand radically affects the tunnel resistance switching and the resistance states' lifetime. That results in a very unique temperature behavior and endows the junctions with multiple degrees of freedom. The obtained results bring up fundamental questions on the interplay between electronic correlations and the creation and mobility of oxygen vacancies in nickelates, opening a new avenue toward mimicking neuromorphic functions by exploiting the electric‐field control of correlated states.

Bipolar interface-type resistive switching effect in the MoS2–xOx film

Bipolar interface-type resistive switching effect in the MoS2–xOx film

Humidity‐Enabled Organic Artificial Synaptic Devices with Ultrahigh Moisture Resistivity

AbstractOrganic memristors with homogeneous resistive switching behaviors can emulate the functionalities of biological synapses, making them promising candidates for use in brain‐inspired neuromorphic computing. Among various environmental parameters, humidity affecting device operational stability is a critical issue that organic memristors face in practical applications. A high humidity resistant organic memristor is demonstrated here using a small molecule material F16CuPc. Unencapsulated devices show excellent moisture stability, maintaining reliable memristive switching behavior after 1 year of exposure to air at 60% high relative humidity and remaining operational when immersed in water for 96 h. A proton conduction mechanism is discovered responsible for the resistive switching effect. The continuously adjustable conductance in F16CuPc‐based memristive devices enables the mimicking of biological synapse functions. These results open up a path to a humidity tolerant neuromorphic computing system based on high humidity resistant artificial synapse devices.

Multilevel halide perovskite memristors based on optical & electrical resistive switching effects

With the aim of addressing the growing challenge of approaching the end of Moore's law and von Neumann bottleneck, the evolution of neuromorphic computing based on memristors that emulate the behaviors of the brain has attracted great attention. Organic-inorganic hybrid lead halide perovskites with inherent hybrid ionic-electronic conduction ability have been proposed as promising candidates for memristors to replace traditional charge-based memory. Here we propose MA0.85Cs0.15PbI3 memristors with high surface crystallinity and stable operation in the atmospheric environment by mixing inorganic cation Cs+ and organic cation MA+. The prepared memristors present excellent resistive switching performances including low operation voltage, high ON/OFF ratio, stable endurance, long retention, and robustness under ambient condition. Besides that, four distinct resistance states have been obtained in the above devices by modifying the operation voltages. Moreover, the resistance switching processes can be controlled both by electrical field and light illumination. Finally, this research provides utilization potentiality in the optical and electrical two-dimension controlled multilevel information devices with a total of five stable resistance states. The present work would offer an effective way to develop multifunctional high-density data-storage applications by storing multiple resistance states in a single unit cell.

A method to improve the performance of all-inorganic halide perovskite CsPbBr3 memory

All-inorganic perovskite has been generally used in memristor due to its outstanding characteristics such as superior optical performance, superior stability, tunable and highly effective photoluminescence. We have proved the use of all-inorganic halide perovskite as a medium in memristor. In this paper, the memristor with construction of Au/CsPbBr3/FTO, Au/CsPbBr3/ZnO/FTO and Au/ZnO/CsPbBr3/FTO were manufactured by one-step spin-coating approach to observe representative bipolar resistance switching behaviors in different construction of resistance random access memory devices. Results show that the memristor based on ZnO/CsPbBr3 heterojunction having excellent resistance switching effect with low resetting, setting voltages and and high environmental stability. Moreover, a model of filaments through the CsPbBr3 layer was raised to interpret the resistive switching effect.

Effect of Nd and Mn Co-Doping on Dielectric, Ferroelectric and Photovoltaic Properties of BiFeO3

Bi1−xNdxFe0.99Mn0.01O3 (BNFMO, x = 0.00~0.20) films were epitaxially grown on Nb:SrTiO3 (001) substrates using pulsed laser deposition. It was found that the Nd-doping concentration has a great impact on the surface morphology, crystal structure, and electrical properties. BNFMO thin film with low Nd-doping concentration (≤16%) crystallizes into a rhombohedral structure, while the high Nd-doping (>16%) will lead to the formation of an orthogonal structure. Furthermore, to eliminate the resistive switching (RS) effect, a positive-up–negative-down (PUND) measurement was applied on two devices in series. The remnant polarization experiences an increase with the Nd-doping concentration increasing to 16%, then drops down with the further increased concentration of Nd. Finally, the ferroelectric photovoltaic effect is also regulated by the ferroelectric polarization, and the maximum photocurrent of 1758 μA/cm2 was obtained in Bi0.84Nd0.16Fe0.99Mn0.01O3 thin film. BNFMO films show great potential for ferroelectric and photovoltaic applications.

Effect of temperature variations on the behavior of a two-terminal organic–inorganic halide perovskite rewritable memristor for neuromorphic operations

Emulation of biological signal processing, learning and memory functions is essential for the development of artificial learning circuitry. Here, we report on the fabrication of organic–inorganic hybrid perovskite based two-terminal rewritable memristor for neuromorphic operations. We investigated the temperature variations in the current-voltage (I–V) characteristics behavior of a two-terminal organic–inorganic perovskite – graphene oxide rewritable memristor in planar geometry. The resistance switching effect has been found to have a switching time of ∼40 ns and it is more pronounced at temperatures below 250 K, then ionic conductivity freezes and electron transport predominates. This effect is observed at both: positive and negative voltages and the hysteresis of the I-Vs decreases significantly at T < 250 K. The change in conductance at temperatures from 290 K down to 100 K is attributed to the transition from ion migration to electronic conduction under external electric field with possible influence of phase structural transition in perovskite film at T < 200 K.

Cu x S nanosheets with controllable morphology and alignment for memristor devices

In electrochemical metallization memristor, the performance of resistive switching (RS) is influenced by the forming and fusing of conductive filaments within the dielectric layer. However, the growth of filaments, mostly, is unpredictable and uncontrollable. For this reason, to optimize ions migration paths in the dielectric layer itself in the Al/Cu x S/Cu structure, uniform Cu x S nanosheets films have been synthesized using anodization for various time spans. And the Al/Cu x S/Cu devices show a low operating voltage of less than 0.3 V and stable RS performance. At the same time, a reversible negative differential resistance (NDR) behavior is also demonstrated. And then, the mechanism of repeatable coexistence of RS effect and NDR phenomenon is investigated exhaustively. Analyses suggest that the combined physical model of space-charge limited conduction mechanism and conductive filaments bias-induced migration of Cu ions within the Cu x S dielectric layer is responsible for the RS operation, meanwhile, a Schottky barrier caused by copper vacancy at the Cu x S/Cu interface is demonstrated to explain the NDR phenomenon. This work will develop a new way to optimize the performance of non-volatile memory with multiple physical attributes in the future.

Electric field manipulation of nonvolatile magnetization in MgO-based memory device with resistive switching effect

In the development of multifunctional data storage devices, controlling magnetic properties by electric field would be highly desirable. This work reported the relationship of magnetic properties of MgO film on porous anodic alumina (PAA) substrates to the different resistance states of Ag/MgO/PAA/Al(Ag/MP/Al) device at room temperature. We suggest that the fully deterministic magnetic switching in this composite film is based on the high sensitivity of oxygen vacancy defect-based conductive filaments to electric field. Our review offers a convenient way to control the magnetic properties using electric field, and shows great promises for developing novel multifunctional material in the future.

Resistive switching effect in RE-Doped cobalt ferrite nanoparticles

Spinel ferrite along with numerous important properties, also exhibit resistive switching effect. Cerium (Ce) doped Co-ferrite nanoparticles having composition CoFe2-xCexO4 (where x = 0.0, 0.05, 0.15, 0.20) were synthesized by co-precipitation synthesis route. X-ray Diffraction analysis confirmed the formation of cubic spinel phase with minor amount of impurities. Frequency dependent dielectric and electrical properties were studied at room temperature within frequency range of 20 Hz to 3 MHz. Dielectric constant, dielectric losses and AC conductivity decreases with cerium substitutions which is usual trend observed in ferrite materials. Modified Debye function was employed to fit Dielectric constant (ε′)- frequency (f) data. Jonscher's power law was employed to study AC conductivity. DC resistivity decreased with increasing temperature. DC resistivity and drift mobility decreased with cerium substitution while activation energy increased. Current–Voltage (I–V) curves of the synthesized composition were studied at room temperature. Current–Voltage (I–V) curves showed nonlinear hysteresis loop like behavior. Current follow different values for forward and reversed applied DC voltage which confirmed that resistive switching effect exit in studied samples. Sample with Ce composition x = 0.25 exhibit larger hysteresis loop than that of other compositions. This shows that sample for Ce composition x = 0.25, can be employed for nonvolatile Resistive Random-Access Memory (ReRAM) applications. Resistive switching effect was explained by utilizing Space-charge-limited current (SCLC) conduction model and by formation of a Schottky barrier at the metal-semiconductor interface.

Highly-sensitive fire alarm system based on cellulose paper with low-temperature response and wireless signal conversion

Highly sensitive smart sensors for early fire detection with remote warning capabilities are urgently required to improve the fire safety of combustible materials in diverse applications. The highly-sensitive fire alarm can detect fire situation within a short time quickly when a fire disaster is about to occur, which is conducive to achieve fire tuned. Herein, a novel fire alarm is designed by using flame-retardant cellulose paper loaded with graphene oxide (GO) and two-dimensional titanium carbide (Ti3C2, MXene). Owing to the excellent temperature dependent electrical resistance switching effect of GO, it acts as an electrical insulator at room temperature and becomes electrically conductive at high temperature. During a fire incident, the partial oxygen-containing groups on GO will undergo complete removal, which results in the conductivity transformation.Besides the use of GO feature, this work also introduces conductive MXene to enhance fire detection speed and warning at low temperature, especially below 300 {\deg}C. The designed flame-retardant fire alarm is sensitive enough to detect fire incident, showing a response time of 2 s at 250 {\deg}C, which is calculated by a novel and quantifiable technique. More importantly, the designed fire alarm sensor is coupled to a wireless communication interface to conveniently transmit fire signal remotely. Therefore, when an abnormal temperature is detected, the signal is wirelessly transmitted to a liquid crystal display (LCD) screen when displays a message such as "FIRE DANGER". The designed smart fire alarm paper is promising for use as a smart wallpaper for interior house decoration and other applications requiring early fire detection and warning.

Tuning Resistive Switching Behavior by Controlling Internal Ionic Dynamics for Biorealistic Implementation of Synaptic Plasticity

AbstractMemristive devices have demonstrated rich switching behaviors that closely resemble synaptic functions and provide a building block to construct efficient neuromorphic systems. It is demonstrated that resistive switching effects are controlled not only by the external field, but also by the dynamics of various internal state variables that facilitate the ionic processes. The internal temperature, for example, works as a second‐state variable to regulate the ion motion and provides the internal timing mechanism for the native implementation of timing‐ and rate‐based learning rules such as spike timing dependent plasticity (STDP). In this work, it is shown that the 2nd state‐variable in a Ta2O5‐based memristor, its internal temperature, can be systematically engineered by adjusting the material properties and device structure, leading to tunable STDP characteristics with different time constants. When combined with an artificial post‐synaptic neuron, the 2nd‐order memristor synapses can spontaneously capture the temporal correlation in the input streaming events.

Effect of Dielectric Thickness on Resistive Switching Polarity in TiN/Ti/HfO2/Pt Stacks

In recent years, several materials and metal-insulator-metal devices are being intensively studied as prospective non-volatile memories due to their resistive switching effect. In this work, thickness-dependent resistive switching polarity was observed in TiN/Ti/HfO2/Pt structures as the sign of the voltages at which SET and RESET occur depended on the film thickness. A thorough revision of the previous literature on bipolar resistive switching polarity changes is made in order to condense previous knowledge of the subject in a brief and comprehensible way and explain the experimental measurements. The different resistive switching polarities occur in a similar voltage range, which is a new finding when compared to precedent research on the subject. A hypothesis is proposed to explain the change in resistive switching polarity, based on the assumption that polarity change is due to filament disruption occurring at different interfaces.

Resistive switching effect in the n-InGaAs/GaAs heterostructures with double tunnel-coupled quantum wells

The electric conductivity behavior in the single and double tunnel-coupled quantum wells (QW) with different doping profile caused by the impact of short pulses of the strong longitudinal (in the quantum wells plane) electric field has been investigated. It is established that at low temperatures (4 K) after such an impact the long-term metastable state with increased electric conductance may be observed in the case of the asymmetric QW couple with the impurity delta shaped-layer in the narrower QW. It is not observed in the structures with other configurations. The observed effect is explained by the model accounting for metastable changes in the electron energy states spectrum in the studied structures caused by the strong electric field pulses.

Nanoscale-Resistive Switching in Forming-Free Zinc Oxide Memristive Structures.

This article presents the results of experimental studies of the impact of electrode material and the effect of nanoscale film thickness on the resistive switching in forming-free nanocrystalline ZnO films grown by pulsed laser deposition. It was demonstrated that the nanocrystalline ZnO film with TiN, Pt, ZnO:In, and ZnO:Pd bottom electrodes exhibits a nonlinear bipolar effect of forming-free resistive switching. The sample with Pt showed the highest resistance values RHRS and RLRS and the highest value of Uset = 2.7 ± 0.4 V. The samples with the ZnO:In and ZnO:Pd bottom electrode showed the lowest Uset and Ures values. An increase in the number of laser pulses from 1000 to 5000 was shown to lead to an increase in the thickness of the nanocrystalline ZnO film from 7.2 ± 2.5 nm to 53.6 ± 18.3 nm. The dependence of electrophysical parameters (electron concentration, electron mobility, and resistivity) on the thickness of the forming-free nanocrystalline ZnO film for the TiN/ZnO/W structure was investigated. The endurance test and homogeneity test for TiN/ZnO/W structures were performed. The structure Al2O3/TiN/ZnO/W with a nanocrystalline ZnO thickness 41.2 ± 9.7 nm was shown to be preferable for the manufacture of ReRAM and memristive neuromorphic systems due to the highest value of RHRS/RLRS = 2307.8 ± 166.4 and low values of Uset = 1.9 ± 0.2 V and Ures = −1.3 ± 0.5 V. It was demonstrated that the use of the TiN top electrode in the Al2O3/TiN/ZnO memristor structure allowed for the reduction in Uset and Ures and the increase in the RHRS/RLRS ratio. The results obtained can be used in the manufacturing of resistive-switching nanoscale devices for neuromorphic computing based on the forming-free nanocrystalline ZnO oxide films.

Percolation effect impact on resistive switching of structures based on nanocomposite (Co-=SUB=-40-=/SUB=-Fe-=SUB=-40-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(LiNbO-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=-

Comparative studies of resistive switching (RS) effect of metal/nanocomposite/metal (M/NC/M), metal/nanocomposite/LiNbO3/metal (M/NC/LNO/M) structures based on NC (Co40Fe40B20)x(LiNbO3)100-x (x=6-20 at.%) with CoFe nanogranules 2-4 nm in size, as well as structures without a NC layer (M/LNO/M), have been carried out. It was found that the percolation conductivity in NC and presence of a thin LNO layer play a key role in the RS effect. When the metal content approaches the percolation threshold of M/NC/M structures (xp~10 at.%), low-resistance percolation nanochannels of granules are formed in structures with an embedded LNO layer, which ensure their stable RS, which, however, are noticeably suppressed as x decreases relative to xp by Delta x~1-2 at.%. Keywords: resistive switching, memristor, nanocomposite, percolation.

Влияние эффекта перколяции на резистивные переключения структур на базе нанокомпозита (Co-=SUB=-40-=/SUB=-Fe-=SUB=-40-=/SUB=-B-=SUB=-20-=/SUB=-)-=SUB=-x-=/SUB=-(LiNbO-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=-

Comparative studies of resistive switching (RS) effect of metal/nanocomposite/metal (M/NC/M), metal/nanocomposite/LiNbO3/metal (M/NC/LNO/M) structures based on NC (Co40Fe40B20)х(LiNbO3)100-x (x = 6–20 at.%) with CoFe nanogranules 2–4 nm in size, as well as structures without a NC layer (M/LNO/M), have been carried out. It was found that the percolation conductivity in NC and presence of a thin LNO layer play a key role in the RS effect. When the metal content approaches the percolation threshold of M/NC/M structures (xp ≈ 10 at.%), low-resistance percolation nanochannels of granules are formed in structures with an embedded LNO layer, which ensure their stable RS, which, however, are noticeably suppressed as x decreases relative to xp by Δх ≈ 1-2 at.%.