Resistive Switching Performance Research Articles

Enhanced resistive switching performance in TiN/AlOx/Pt RRAM by high-temperature I-V cycling

Set voltage is a key parameter for the application of Resistance Random Access Memory (RRAM). In this paper, based on TiN/AlOx/Pt RRAM synthesized by the magnetron sputtering method, we have studied the influence of I-V cycling at high temperatures on resistive switching performance. The results show that the treatment can significantly reduce the set voltage in resistive switching cycles. Moreover, the treatment can also enhance endurance effectively. Further studies indicated that a higher compliance current in treatment can induce a smaller and more uniform set voltage. We ascribe the improvements in resistive switching performance to the generation and accumulation of oxygen vacancies in the treatment. This research provides new ideas for synthesizing RRAM devices with low power consumption.

Effect of Temperature on TiO2/P‐Si‐Based Memristor Devices as Optical/Electrical Synapse

Light‐based modulation on resistive switching has opened a new route for development of the devices for advanced applications like integrated switching with memory functionality, neuromorphic computing, and humanoid robotics. This article presents the wafer‐scalable process to fabricate titanium dioxide (TiO2)/porous silicon (P‐Si)‐based heterostructures for memristor applications. The resistive switching performance of the memristor is analyzed using electrical/optical stimulation. The fabricated devices offer enhanced performance metrics during optical stimulation when compared to electrical stimulation. The memristor device offers the paired pulse facilitation (PPF) index of ≈519% (during optical stimulation), which is 3.4 times of the electrical stimulation. Further, the stability and reliability measurements are performed at different temperatures especially (room temperature to 348 K) under 450 nm illumination. The testing results prove that the developed TiO2/P‐Si‐based memristors are suitable for the next‐generation computation systems development.

Laser assembly of CeO2 nanobrushes and their resistive switching performance

Memristors in a metal/oxide/metal configuration emerge as an advanced non-volatile information storage technology due to their high operating speed and low power consumption. Understanding the role of the microstructure of the active oxide layer in its resistive switching (RS) performance is scientifically important for revealing the conduction mechanism of oxides, and technically critical for the development of high-performance memristors. Here, self-assembly of vertically aligned CeO2 nanobrushes, a typical RS material, is demonstrated in pulsed laser epitaxy. The growth map of CeO2 is fully explored, and optimized growth conditions for CeO2 nanobrushes are established. Microstructure and crystallinity characterizations reveal the single-crystalline epitaxy nature of CeO2 nanobrushes. A nanobrush memristor exhibits a threshold switching feature with an On/Off ratio of 50, as 16 times high as a thin-film memristor, and excellent endurance of up to 500 cycles and retention time of up to 104 seconds. Theoretical fitting of the I-V curves of the thin-film and nanobrush memristors show interfacial switching in the thin-film memristor and filamentary switching in the nanobrush memristor. The distinct RS mechanisms between thin films and nanobrushes suggest the fundamental role of the structural design of active oxide layers in the RS performance of oxide-based memristors.

Synergetic engineering of oxidizable, redox, and inert metal decorated copper oxide for non-volatile memory and neuromorphic computing applications

Abstract In the quest for efficient resistive switching (RS) materials for both non-volatile memory and neuromorphic computing applications, a variety of functional materials have been researched in the last few years. Herein, we systematically synthesized Ni, Ag, and Au decorated copper oxide (CuxO) by using an electrochemical approach and investigated their RS performance for both non-volatile memory storage and neuromorphic computing applications. By tuning various electrochemical parameters, we optimized Ni, Ag, and Au decoration over the CuxO switching layers to understand the effect of oxidizable, redox, and inert metal decoration, respectively. Fabricated Ni-CuxO/FTO, Ag-CuxO/FTO, and Au-CuxO/FTO devices show forming-free bipolar and analog properties of RS behavior. The electrical measurements asserted that the electrodeposited Ni-CuxO/FTO RS device shows excellent RS, non-volatile memory, and synaptic learning properties compared to the Ag-CuxO/FTO, and Au-CuxO/FTO devices. Moreover, the statistical and Weibull distribution parameters suggested that the Ni-CuxO/FTO RS device has lower switching variation than the other two devices. The conduction mechanisms of all devices are investigated by fitting the appropriate physics-oriented models. It was found that Ohmic and Child's square law were dominated during the charge transport and the RS process occurred due to the filamentary switching effect. Results suggested the electro-decorated/-deposited Ni-CuxO is a suitable switching layer for memory as well as neuromorphic computing applications.

Robust resistance switching performance in a Ca3Ti2O7/La0.67Sr0.33MnO3 heterostructure induced by the interface

Ruddlesden–Popper phase oxides, such as Ca3Ti2O7, have been established as hybrid improper ferroelectrics. However, investigations into Ca3Ti2O7 have primarily concentrated on their structural and ferroelectric properties. In this study, we prepared epitaxial Ca3Ti2O7 thin films via magnetron sputtering. Conducting atomic force microscopy was employed to characterize local current variations under an applied bias voltage. Electron paramagnetic resonance measurements of the Ca3Ti2O7/La0.67Sr0.33MnO3 film were conducted to assess its defect characteristics. Interestingly, the Ca3Ti2O7/La0.67Sr0.33MnO3 stacks exhibited remarkable macroscopic resistance switching, with a resistance on/off ratio reaching 100, alongside robust retention (∼2500 s) and endurance (∼2000 cycles) features. Additionally, density functional theory calculations suggest that the resistance switching is attributable to the interface barrier of the Ca3Ti2O7/La0.67Sr0.33MnO3 interface and the efficacy of space charge limitation. This work proposes an avenue for the utilization of Ruddlesden–Popper phase Ca3Ti2O7 in various applications.

Synthesis of Copper Sulfides by Anion Substitution and their Resistive Switching Properties in the Presence of Cuprou‘s

AbstractCopper sulfides exhibit various significant physical properties and have wide potential applications. In order to synthesize copper sulfides and investigate the anion substitution possibility of Cu3P, we immersed Cu3P in sodium sulfide solution. From X‐ray diffraction spectra results, copper sulfides, namely Cu2S and Cu7.2S4, were observed, indicating that anion substitution between S2− and P3− ions did occur. Consequently, we investigated the resistive switching (RS) properties of these two phases in the presence of Cu3P. We found that the Cu2S‐Cu3P composite exhibited a high Off/On ratio (88) and a long retention time (>103 s). However, the Cu7.2S4‐Cu3P composite exhibited no RS performance. In addition, we discussed the conduction and resistive switching mechanisms. Our work enriches the preparation method of copper sulfides and provides a reference for enhancing RS performance.

Coexistence of digital and analog resistive switching behaviors in nanocrystalline yttrium-iron-garnet thin films achieved by electrode engineering

Memristors with digital or analog resistive switching characteristics have the potential to acquire high-performance data storage or electronic synaptic device applications, respectively. It is considerably important to realize coexistence of digital and analog resistive switching characteristics for high-performance memristor applications. In this study, the nanocrystalline yttrium-iron-garnet Y3Fe5O12 (YIG) thin film was synthesized on Pt substrates by a facile solution-processed method, and it can be used as resistive switching layer for fabricating memory devices. The digital and analog resistive switching characteristics in YIG thin film devices were achieved by employing inert platinum and active silver electrodes, respectively. Oxygen vacancy-controlled conductive filaments (CFs) with Pt/YIG/Pt structure exhibited digital resistive switching behavior which can be modulated by changing voltage polarity. The resistive switching mode with positive Set/Reset in the Pt/YIG/Pt device acquired superior resistive switching properties. Ag/YIG/Pt device exhibited analog resistive switching characteristics based on the formation of Ag-based CFs. The conductance increase during Set operation and decrease during Reset process by adjusting current gradients and voltage windows, respectively. The present study exhibits an effective path to obtain the digital and analog resistive switching properties, which opens a door for understanding and optimizing resistive switching performance.

MemriSim: A theoretical framework for simulating electron transport in oxide memristors

We have developed a theoretical framework MemriSim for simulating the resistive switching behaviors of oxide memristors. MemriSim comprises two major parts, i) structural evolution of oxygen vacancies during conductive filament formation/rupture by kinetic Monte Carlo (kMC) algorithm, and ii) transport calculations based on the scenario of electron tunneling and thermionic emission with the kMC derived structures. As prototype probes, we have computed the current-voltage (I-V) curves of HfO2 and TaOx based memristors and compared the results with experimental measurements, which show perfect agreement. By tuning the physical parameters, MemriSim can describe resistive switching devices with different oxide layers and metal electrodes. In addition, the pulse transient current can also be simulated by considering the transient response of RLC circuit. The developed framework not only provides a general approach for understanding the fundamental mechanism of resistive switching in oxides, but also opens up new opportunities for designing and optimizing memristor-based architectures for nonvolatile memory, logic-in-memory and neuromorphic computing.Program summaryProgram Title: MemriSim.CPC Library link to program files: https://doi.org/10.17632/8gbbgf8z49.1Licensing provisions: GPLv2.Programming language: C++.Supplementary material: Supplementary material is available.Nature of problem: A general framework for simulating the resistive switching properties of oxide-based memristors; generate the structure of oxide layer during filament formation/rupture; calculate the I-V curves of memristive device; simulate the pulse transient current; predict the resistive switching performance of new devices.Solution method: The framework uses kMC algorithm for structural evolution, the electric field inside oxide layer is computed by the Poisson's equation, and the transport calculation is based on electron tunneling and thermionic emission.

Validation of van der Waals Interface for Enhanced Resistive Switching Performance in Memristor by Using Topotactic Phase Transition Material

Validation of van der Waals Interface for Enhanced Resistive Switching Performance in Memristor by Using Topotactic Phase Transition Material

Scalable Layer-Controlled Oxidation of Bi2O2Se for Self-Rectifying Memristor Arrays With sub-pA Sneak Currents.

Smart memristors with innovative properties are crucial for the advancement of next-generation information storage and bioinspired neuromorphic computing. However, the presence of significant sneak currents in large-scale memristor arrays results in operational errors and heat accumulation, hindering their practical utility. This study successfully synthesizes a quasi-free-standing Bi2O2Se single-crystalline film and achieves layer-controlled oxidation by developing large-scale UV-assisted intercalative oxidation, resulting β-Bi2SeO5/Bi2O2Se heterostructures. The resulting β-Bi2SeO5/Bi2O2Se memristor demonstrates remarkable self-rectifying resistive switching performance (over 105 for ON/OFF and rectification ratios, as well as nonlinearity) in both nanoscale (through conductive atomic force microscopy) and microscale (through memristor array) regimes. Furthermore, the potential for scalable production of self-rectifying β-Bi2SeO5/Bi2O2Se memristor, achieving sub-pA sneak currents to minimize cross-talk effects in high-density memristor arrays is demonstrated. The memristors also exhibit ultrafast resistive switching (sub-100ns) and low power consumption (1.2 pJ) as characterized by pulse-mode testing. The findings suggest a synergetic effect of interfacial Schottky barriers and oxygen vacancy migration as the self-rectifying switching mechanism, elucidated through controllable β-Bi2SeO5 thickness modulation and theoretical ab initio calculations.

BiFeO3/SrTiO3 superlattice-like based ferroelectric memristors with pronounced artificial synaptic plasticity

Memristors are attracting widespread attention for their multilevel storage capacity and synaptic learning ability. Ferroelectric memristors, with resistance switching based on polarization reversal, offer uniform threshold voltage and analog resistance modulation. By preparing superlattice-like ferroelectric films, the ferroelectric properties can be significantly enhanced, thereby improving the memristive characteristics. In this study, the constructed BiFeO3/SrTiO3 (BFO/STO) superlattice-like structure increases the remanent polarization by approximately 200 % compared to a single-layer BFO structure, as well as the dramatically enhanced resistance switching performance. Notably, the Pt/(BFO/STO)2/NSTO device shows superior storage performance, with extended endurance (1000 cycles), reliable retention (10000 seconds) and fundamental synaptic behaviors being demonstrated. Finally, simulations for handwritten digit recognition classification, involving modulation of conductance to vary synaptic weights, achieve an impressive accuracy of 87.46 %, showing great promising for applications in information storage and neuromorphic computing.

Bipolar resistive switching behavior of PVA/g-C3N4 quantum dots hybrid thin films

Graphite-phase carbon nitride quantum dots (g-C3N4 QDs) have garnered widespread attention and considerable research interest as active media for resistive random-access memory (RRAM) devices owing to their exceptional physical properties. In this study, g-C3N4 QDs were synthesized via ultrasonic-assisted liquid-phase exfoliation. Subsequently, the obtained g-C3N4 QDs with uniform size were embedded into polyvinyl alcohol (PVA) for preparing PVA/g-C3N4 QDs hybrid, and the RRAM devices with Al/g-C3N4 QDs-PVA/ITO/PET structure were fabricated. The obtained memory devices exhibit bipolar resistive switching (BRS) behavior and are primarily influenced by the space charge limited conduction (SCLC) mechanism. The data retention time exceeds 104 s at a read voltage of 0.1 V, accompanied by an impressively low set voltage. In addition, the device exhibits a surprising temperature dependence of the resistive switching performance at different temperatures. The aforementioned properties demonstrate the significant potential of g-C3N4 QDs in RRAM for data storage applications.

Advances on MXene-Based Memristors for Neuromorphic Computing: A Review on Synthesis, Mechanisms, and Future Directions.

Neuromorphic computing seeks to replicate the capabilities of parallel processing, progressive learning, and inference while retaining low power consumption by drawing inspiration from the human brain. By further overcoming the constraints imposed by the traditional von Neumann architecture, this innovative approach has the potential to revolutionize modern computing systems. Memristors have emerged as a solution to implement neuromorphic computing in hardware, with research based on developing functional materials for resistive switching performance enhancement. Recently, two-dimensional MXenes, a family of transition metal carbides, nitrides, and carbonitrides, have begun to be integrated into these devices to achieve synaptic emulation. MXene-based memristors have already demonstrated diverse neuromorphic characteristics while enhancing the stability and reducing power consumption. The possibility of changing the physicochemical properties through modifications of the surface terminations, bandgap, interlayer spacing, and oxidation for each existing MXene makes them very promising. Here, recent advancements in MXene synthesis, device fabrication, and characterization of MXene-based neuromorphic artificial synapses are discussed. Then, we focus on understanding the resistive switching mechanisms and how they connect with theoretical and experimental data, along with the innovations made during the fabrication process. Additionally, we provide an in-depth review of the neuromorphic performance, making a connection with the resistive switching mechanism, along with a compendium of each relevant performance factor for nonvolatile and volatile applications. Finally, we state the remaining challenges in MXene-based devices for artificial synapses and the next steps that could be taken for future development.

Light-induced multilevel resistive switching in cesium-doped lead-free halide double perovskite memory device

A series of (CH3NH3)2-xCsxAgBiBr6 films (x=0, 0.1, 0.2, 0.3, 0.4) were fabricated on ITO/glass substrates through the sol-gel method. 15 % Cs doping (x=0.3) was the optimal condition for enhancing the film quality and achieving nonvolatile bipolar resistive switching (BRS) performance in the devices. The on/off ratio in the (CH3NH3)1.7Cs0.3AgBiBr6 (Cs-MAABB-3)-based RS device reached 7.7×104, high and low resistance states were maintained for over 104 s. Under different light intensities with a wavelength of 430 nm, six distinct resistance states were recorded at −0.3 V in the Au/Cs-MAABB-3/ITO/glass device. These multilevel states remained after 5000 s and 650 cycles, indicating the excellent retention and endurance of multilevel RS memory in the Au/Cs-MAABB-3/ITO/glass device. The RS behavior in this device followed the trap-controlled space charge-limited current and conductive filament models. Cs-doping increased the concentration of intrinsic vacancies appropriately, leading to a more prominent RS effect. With varying intensities of illumination, the change of Schottky-like barrier at the Au/Cs-MAABB-3 interface, modulated by the photo-induced carriers, affected the multilevel resistance states in the device. The excellent multilevel RS performance was observed for the first time in the Cs-MAABB-3-based device. It presents broad possibilities for improving high-density memory in lead-free halide double perovskite-based devices.

A Multimodal Perception-Enabled Flexible Memristor with Combined Sensing-Storage-Memory Functions for Enhanced Artificial Injury Recognition.

With the continuous advancement of wearable technology and advanced medical monitoring, there is an increasing demand for electronic devices that can adapt to complex environments and have high perceptual sensitivity. Here, a novel artificial injury perception device based on an Ag/HfOx/ITO/PET flexible memristor is designed to address the limitations of current technologies in multimodal perception and environmental adaptability. The memristor exhibits excellent resistive switching (RS) performance and mechanical flexibility under different bending angles (BAs), temperatures, humid environment, and repetitive folding conditions. Further, the device demonstrates the multimodal perception and conversion capabilities toward voltage, mechanical, and thermal stimuli through current response tests under different conditions, enabling not only the simulation of artificial injury perception but also holds promise for monitoring and controlling the movement of robotic arms. Moreover, the logical operation capability of the memristor-based reconfigurable logic (MRL) gates is also demonstrated, proving the device has great potential applications with sensing, storage, and memory functions. Overall, this study not only provides a direction for the development of the next-generation flexible multimodal sensors, but also has significant implications for technological advancements in many fields such as robotic arms, electronic skin (e-skin), and medical monitoring.

Exploring resistive switching properties and mechanisms in sol-gel derived Gd2Ti2O7 thin films for RRAM applications

This study focused on investigating the effects of film thicknesses and thermal treatments on the resistance-switching characteristics of Gd2Ti2O7-based RRAM devices for the first time. Gd2Ti2O7 thin films were successfully synthesized using a sol-gel deposition technique on ITO/glass substrates as the foundation for this research. The conduction mechanism of the filament was found to be primarily influenced by oxygen vacancies. The study found that annealing at 300 °C resulted in a slight increase in oxygen vacancies and switching cycles. However, annealing at 200 °C and 400 °C led to a significant decrease in oxygen vacancies, resulting in reduced switching cycles. To further enhance the device performance, a post-metal annealing process was applied at 300 °C to form an extra AlOx layer. This additional layer facilitated the coexistence of oxygen vacancies and aluminum ions, promoting the formation of conductive filaments and enhancing the resistive switching performance of the devices. As a result, the device subjected to 300 °C post-metal annealing demonstrated optimized resistive switching properties, including a maximum of 1248 switching cycles, a Ron/Roff ratio of 102, and VSet/VReset = −5.38 V/2.08 V. These findings highlight the promising potential of Gd2Ti2O7-based RRAM devices for practical applications in Resistive Random Access Memory (RRAM).

The resistance switching performance of the memristor improved effectively by inserting carbon quantum dots (CQDs) for digital information processing

The resistance switching performance of the memristor improved effectively by inserting carbon quantum dots (CQDs) for digital information processing

Improvement of switching uniformity in TiO2-based resistive random access memory with graphene oxide embedded film

TiO2-based resistive random access memory (RRAM) devices has the potential to fabricating nonvolatile memory applications. However, the memories based on TiO2 have severe problems like large resistive switching parameter fluctuations, poor cycling endurance and so on, which can be a limitation of the device in practical applications. Graphene oxide (GO) is a novel material that has attracted much attention and is often applied to enhance the performance of memories due to its own special properties. In this work, two types of bilayer structure based on TiO2 for RRAM devices were fabricated. The significant improvement in uniformity of operating voltages and high HRS/LRS ratio of the TiO2-based RRAM were realized by inserting a two-dimensional GO film between TiO2 and FTO. The presence of the GO film would prevent the ion exchange between the electrodes and the switching layer as well as its insulating properties. The conduction mechanisms of all the devices in low and high resistance states were dominant by the Ohmic conduction mechanism and the space charge limited conduction mechanism, respectively. This research manifests the promising potential of two-dimensional GO embedded layer for improving resistive switching performance of RRAMs.

Resistive switching and synaptic characteristics of Hf-doped ZnO sandwiched between HfO2-based memristors for neuromorphic computing

With the rise of neuromorphic computing, memristors have attracted much attention as a device with potential synaptic properties. In this paper, we investigated the embedding of Hf-doped ZnO (Hf:ZnO) layers with different doping concentrations in HfO2-based memristors to design HfO2/(0 %-10 %)Hf:ZnO/HfO2 tri-layer structured memristors for resistive switching (RS) and synaptic characteristics. Utilizing first-principles calculations, we integrated assessments of both oxygen vacancy migration capability and material conductivity to evaluate the rationale behind our design. The experimental results show that the HfO2/(5 %)Hf:ZnO/HfO2 tri-layer structured memristor presents the best RS performance, with a storage window of 103. We analyze the impact of insertion layers with varying doping concentrations on the RS performance of the devices and elucidate the RS mechanism. In addition, we investigated the synaptic properties of HfO2/(5 %)Hf:ZnO/HfO2 tri-layer structured memristor, and effectively simulated synaptic plasticity akin to the synaptic behavior found in biological neurons. Finally, we also constructed a memristor-based Spiking Neural Network for recognizing the Mixed National Institute of Standards and Technology handwritten digit dataset, achieving a recognition accuracy of 82 %. This comprehensive study shows that the insertion of (5 %)Hf:ZnO into HfO2-based memristors holds significant promise for upcoming applications in the field of neuromorphic computing.

Enhanced resistive switching behaviors of organic resistive random access memory devices by adding polyethyleneimine interlayer

Organic nonvolatile memory devices have garnered significant attention as next-generation electrical memory units owing to their potential for low-cost and straightforward fabrication through a solution process. In this study, we successfully fabricated fully solution-processed organic resistive random access memory (RRAM) devices using poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the resistive switching (RS) layer, with poly(3,4-ethylene-dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) employed as the top electrode. Additionally, to enhance performance further, a polyethyleneimine (PEIE) interlayer was introduced between the bottom electrode and the P3HT:PCBM RS layer. The resulting organic RRAM devices with the PEIE interlayer exhibited bipolar resistive switching, with improved endurance increasing from 50 to 100 cycles, a retention time of 103 s, and a low SET voltage of 0.7 V. The organic RRAM devices featuring the PEIE interlayer demonstrated superior RS performance attributed to the higher Schottky barrier at the interface between the bottom electrode and the active switching layer, creating an asymmetric structure. I–V curve fitting confirmed that the potential switching mechanism involved Schottky emission in the high-resistance state and Ohmic conduction in the low-resistance state. Our findings suggest that organic RRAM devices with a PEIE interlayer hold promise for stable nonvolatile memory applications.