Resistive Switching Performance Research Articles

Simulation of the resistance switching performance and synaptic behavior of TiO2-based RRAM devices with CoFe2O4 insertion layers.

The electrothermal coupling model of Pt/CoFe2O4/TiO2/TiN devices was established to study their resistive switching characteristics and basic biological synaptic properties in our research. The processes of set and reset are simulated, and the distribution of the temperature, the electric field and the concentration of oxygen vacancies in the dielectric layer are obtained. The switching performance of the TiO2-based device is significantly improved after the CoFe2O4 layer is inserted, with the switching voltage, working current and power consumption being reduced, while the switching ratio is increased. By changing the thermal conductivity of the top electrode, the rupture position of the conductive filament can be controlled. The I-V characteristics of the Pt/CoFe2O4/TiO2/TiN device during the reset and set processes are fitted linearly in logarithmic coordinates, and the ohmic conduction mechanism or the space-limited charge conduction mechanism is mainly satisfied in the high and low resistance states. Finally, the application of dual-layer devices on biological synapses is studied, and the basic biological characteristics of enhancement, inhibition and paired pulse promotion are simulated successfully. In addition, the redox reaction induced by oxygen vacancy migration also promotes the formation and rupture of the conductive filament. Results of the study show this ferrite material as an insertion layer in a resistive random-access memory structure that offers potential for future information storage and bioneuromorphic computation devices.

Improved resistive switching performance of amorphous InGaZnO-based memristor with the TiO2 insertion layer

A stable I–V repeatability memristor based on amorphous InGaZnO (a-IGZO) with a TiO2 insertion layer was investigated. Two memristive structures composed of Pt/a-IGZO/Pt and Pt/TiO2/a-IGZO/Pt were manufactured on SiO2/Si substrate by the magnetron sputtering method. The crystallization of IGZO thin films was analyzed by the XRD process under different annealing temperatures, and the results show that the thin films remain in a stable amorphous state. The resistive switching performance of the two structures was tested by the semiconductor parameter analyzer 4200-SCS at room temperature. After 30 cyclic scans, the Pt/a-IGZO/Pt structure shows signs of degeneration in its I–V cyclic characteristics. However, in the Pt/TiO2/a-IGZO/Pt structure, the cyclic characteristics of I–V are highly stable (cycles >105 sweeps) with a limiting operating current of 0.01 A. Its rectification ratio is approximately 20 at low operating voltages (±1.0 V), and conductance increases (or decreases) progressively with continuous positive (or negative) voltage scans. Further analysis of the experimental energy band diagram was measured by UV–vis spectra and ultraviolet photoemission spectroscopy (UPS). The results demonstrate that the operational mechanism is the modulation of the barrier at the TiO2/a-IGZO interface, which is conducive to the stable I–V cyclic characteristic of Pt/TiO2/a-IGZO/Pt memristor.

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.

Enhanced Resistive Switching Performances of Mn-Doped BiFeO₃ Memristor by Introducing Oxygen Reservoir Interface

Enhanced Resistive Switching Performances of Mn-Doped BiFeO₃ Memristor by Introducing Oxygen Reservoir Interface

Research Progress on the Application of Topological Phase Transition Materials in the Field of Memristor and Neuromorphic Computing.

Topological phase transition materials have strong coupling between their charge, spin orbitals, and lattice structure, which makes them have good electrical and magnetic properties, leading to promising applications in the fields of memristive devices. The smaller Gibbs free energy difference between the topological phases, the stable oxygen vacancy ordered structure, and the reversible topological phase transition promote the memristive effect, which is more conducive to its application in information storage, information processing, information calculation, and other related fields. In particular, extracting the current resistance or conductance of the two-terminal memristor to convert to the weight of the synapse in the neural network can simulate the behavior of biological synapses in their structure and function. In addition, in order to improve the performance of memristors and better apply them to neuromorphic computing, methods such as ion doping, electrode selection, interface modulation, and preparation process control have been demonstrated in memristors based on topological phase transition materials. At present, it is considered an effective method to obtain a unique resistive switching behavior by improving the process of preparing functional layers, regulating the crystal phase of topological phase transition materials, and constructing interface barrier-dependent devices. In this review, we systematically expound the resistance switching mechanism, resistance switching performance regulation, and neuromorphic computing of topological phase transition memristors, and provide some suggestions for the challenges faced by the development of the next generation of non-volatile memory and brain-like neuromorphic devices based on topological phase transition materials.

Investigation of resistive switching behaviors of cuprous phosphide thick film

In order to find high-performance memristor materials. we prepared cuprous phosphide (Cu3P) thick film by a simple chemical reaction method and studied its resistive switching properties. We investigated the effects of device structure, voltage sweep rate and electrode material on the resistive switching performance. For devices employing various electrode materials, negligible disparities were observed in transition voltage (< 0.35 V), endurance (2 ×103), and retention time (> 4 ×104 s). However, substantial differences were observed in operational speed and Off/On ratio. Specifically, device utilizing stainless steel (SS) electrode exhibited the highest operational speed (5000 V/s), while that employing nickel electrode demonstrated the largest Off/On ratio (2.1 ×104). We also observed that the device status self-healed after a voltage sweep operation. Finally, we discussed electrical switching mechanism. Our work enriches the resistive switching performance and mechanism of Cu3P bulk materials, hoping to provide a reference for the research of memristor materials.

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.

A High‐Entropy‐Oxides‐Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution (Adv. Mater. 41/2023)

A High‐Entropy‐Oxides‐Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution (Adv. Mater. 41/2023)

Influences of Cu Doping on the Microstructure, Optical and Resistance Switching Properties of Zinc OxideThin Films.

Copper-doped zinc oxide films (Zn1-xCuxO) (x = 0, 2%, 4%, 6%) were fabricated on conductive substrates using the sol-gel process. The crystal structure, optical and resistive switching properties of Zn1-xCuxO films are studied and discussed. RRAM is made using Zn1-xCuxO as the resistive layer. The results show that the (002) peak intensity and grain size of Zn1-xCuxOfilms increase from 0 to 6%. In addition, PL spectroscopy shows that the oxygen vacancy defect density of Zn1-xCuxO films also increases with the increase in Cu. The improved resistive switching performance of the RRAM device can be attributed to the formation of conductive filaments and the destruction of more oxygen vacancies in the Zn1-xCuxO film. Consequently, the RRAM device exhibits a higher low resistance state to high resistance state ratio and an HRS state of higher resistance value.

Laser-modulated formation of conduction path for the achievement of ultra-low switching voltage in resistive random-access memory (RRAM)

Energy saving is one of critical issues that must be seriously considered for the development of next-generation memory devices. In this study, an ultralow-power resistive random-access memory (RRAM) device is fabricated through use of a successful modulation of the AlOX layer by a laser treatment optimized for the energy saving in resistive switching (RS). The device shows not only multilevel memory properties but also a high on/off ratio (∼106), good endurance (300 cycles), and excellent retention (>104 s). Most importantly, the laser-modulated device achieves ultra-low set and reset voltages (0.06 V and −0.04 V), leading to a very low-power consumption. It was observed that the amorphous phase in the AlOX layer is transformed into the polycrystalline phase and a concentration gradient of oxygen vacancies is secured. The grain boundaries in the polycrystalline act as pathways to facilitate the movement of oxygen vacancies. Meanwhile, the concentration gradient accelerates the diffusion mobility of the oxygen vacancies. The highly potential application of the laser-modulation to the flexible RRAM devices has been demonstrated by a strong level of RS performance maintenance from a device fabricated using the polyethylene terephthalate (PET) substrate.

A High-Entropy-Oxides-Based Memristor: Outstanding Resistive Switching Performance and Mechanisms in Atomic Structural Evolution.

The application of high-entropy oxide (HEO) has attracted significant attention in recent years owing to their unique structural characteristics, such as excellent electrochemical properties and long-term cycling stability. However, the application of resistive random-access memory (RRAM) has not been extensively studied, and the switching mechanism of HEO-based RRAM has yet to be thoroughly investigated. In this study, HEO (Cr, Mn, Fe, Co, Ni)3 O4 with a spinel structure is epitaxially grown on a Nb:STO conductive substrate, and Pt metal is deposited as the top electrode. After the resistive-switching operation, some regions of the spinel structure are transformed into a rock-salt structure and analyzed using advanced transmission electron microscopy and scanning transmission electron microscopy. From the results of X-ray photoelectron spectroscopy and electron energy loss spectroscopy, only specific elements would change their valence state, which results in excellent resistive-switching properties with a high on/off ratio on the order of 105 , outstanding endurance (>4550 cycles), long retention time (>104 s), and high stability, which suggests that HEO is a promising RRAM material.

Fabrication of AIE Polymer-Functionalized Reduced Graphene Oxide for Information Storage.

Reduced graphene oxide (RGO) has been extensively studied and applied in optoelectronic systems, but its unstable dispersion in organic solvents has limited its application. To overcome this problem, the newly designed and developed aggregation-induced emission (AIE) material poly[(9,9-bis(6-azidohexyl)-9H-fluorene)-alt-(9-(4-(1,2,2-triphenylvinyl)phenyl)-9H-carbazole)] (PAFTC) was covalently grafted onto RGO to produce (PFTC-g-RGO). The solubility of two-dimensional graphene was improved by incorporating it into the backbone of PAFTC to form new functional materials. In resistive random access memory (RRAM) devices, PFTC-g-RGO was used as the active layer material after it was characterized. The fabricated Al/PFTC-g-RGO/ITO device exhibited nonvolatile bistable resistive switching performances with a long retention time of over 104 s, excellent endurance of over 200 switching cycles, and an impressively low turn-ON voltage. This study provides important insights into the future development of AIE polymer-functionalized nanomaterials for information storage.

Facile one-pot electropolymerization of novel Cu complexed conducting polymer for Resistive Random Access Memory

An innovative one-pot electrochemical method has been studied for the Polypyrrole-Cu (PPy-Cu) composite films synthesis as the active layer of the Resistive Random Access Memory (ReRAM). Cu has been uniformly distributed in PPy-Cu composite films and exhibits two valence states of Cu (0) and Cu (II). The existence of Cu (II) is beneficial for keeping stable resistive switching performance. The Pt/PPy-Cu/Pt ReRAM device exhibits excellent memory performance with a low threshold voltage, a long retention time and good endurance cycles. The resistive switching mechanism is dominated by the Space Charge Limited Current (SCLC) effect accompanied by Schottky emission.

Graphene Quantum Dots as an Oxygen Reservoir for Topotactic Phase Transition‐Based Memristive Devices

AbstractA novel class of transition metal oxides, capable of reversible topotactic phase transition between the oxygen‐deficient brownmillerite and oxygen‐rich perovskite, has emerged as a promising material for memristive and magnetoelectric devices. However, the absence of a local oxygen source in the device structure necessitates an oxygen exchange process between the surrounding atmosphere and the switching layer during operation, which can lead to unreliable device performance. In this study, graphene quantum dots (GQDs) are introduced into a SrFe0.5Co0.5Ox memristive device as an oxygen reservoir for the nanoscale topotactic redox process. The SrFe0.5Co0.5Ox memristive devices with GQDs exhibit reliable resistive switching performance compared to SrFe0.5Co0.5Ox devices without GQDs. To understand the effect of GQDs on the device structure, a pulse endurance test is carried out in a high vacuum. The devices with GQDs show rather good endurance behavior, while devices without GQDs exhibit endurance failure. These results provide a deeper understanding of the potential use of GQDs in enhancing the performance of SrFe0.5Co0.5Ox memristive devices, with implications for tuning nanoscale topotactic phase transition for multi‐functional properties.

Improved resistive switching performance and mechanism analysis of MoO3 nanorods based memristors

Low dimensional nanomaterials have distinctive physical, chemical, and electrical characteristics, which have led to their widespread use in the preparation of sensors, optoelectronic devices, and nonvolatile memory devices in recent years. MoO3 nanomaterials are transition metal oxides with high work functions and broadband gaps, which have potential applications in electronic, electrochromic, and battery devices. In this work, Ag/MoO3/Ti memristive device was prepared by annealing MoO3 nanospheres, which can improve resistive switching (RS) behavior. In other words, one-dimensional (1D) MoO3 nanorods with uniform size and dense connections was obtained by annealing MoO3 nanospheres at 300 ℃. The RS behavior of the Ag/MoO3/Ti memristor presents obvious nonvolatile memory characteristics with larger resistance window at room temperature. In particular, the device shows N-type negative differential resistance (NDR) effect at relatively high positive voltage region. Based on the obtained data, the RS behavior conduction mechanism of the Ag/MoO3/Ti device was discussed by establishing physical models of Ohmic conduction and Schottky emission. This work establishes the foundation for further understanding the working mechanisms of memristors and exploring potential applications of low dimensional material based memristors.

Enhanced memristor performance via coupling effect of oxygen vacancy and ferroelectric polarization

As a new type of nonvolatile memory, the resistive memristor has broad application prospects in information storage and neural computing based on its excellent resistive switching (RS) performance. At present, it is still a great challenge to improve both ferroelectric polarization and leakage current to achieve a high RS on/off ratio of ferroelectric memristors. Herein, epitaxial Pb(Zr0.40Ti0.60)O3 (PZT) thin films with low content Ca doping were deposited on the Nb:SrTiO3 substrate to prepare PCZT/NSTO heterostructures and their RS behaviors were studied. The research findings show that compared with pure PZT film, the ferroelectric polarization of 1-mol%-Ca-doped PZT film is slightly improved, while the leakage current is increased by three orders of magnitude. Therefore, the RS on/off ratio reaches 2.5 × 105, about three orders of magnitude higher than pure PZT films. The theoretical analysis reveals that the RS behavior of PCZT/NSTO heterostructures is controlled by the PCZT/NSTO interfacial barrier and the space charge-limited current mechanism. Our results demonstrate that the ferroelectricity and electricity of ferroelectric thin films can be improved simultaneously by doping low-content Ca ions to increase the RS performance, which provides a good reference for the development of high-performance ferroelectric memristor devices.

High-performance Ta2O5-based resistive random-access memory with embedded graphene quantum dots and Pt–Ag composite active layer

Resistive random-access memory (RRAM) has garnered significant interest in developing nonvolatile memory systems due to its ability to provide external field tunable resistive states with fast speed and low power consumption. This tunable resistive state primarily results from the formation and breakage of conductive pathways triggered by active ion migration. However, due to the stochastic nature of ion migration, the stability of the switching process is a long-standing bottleneck. Here, we investigate the impact of device kinetic parameters on the stability of resistive switching behavior and propose a high-performance RRAM with a Pt–Ag/Ta2O5/GQDs/Pt structure. Incorporating quantum dots can regulate the direction of Ag ion migration, while the Pt–Ag composite electrode can manipulate the oxidation rate of Ag atoms. Compared to the Ag/Ta2O5/GQDs/Pt device, the Pt–Ag/Ta2O5/GQDs/Pt device exhibited a 15-fold reduction in operating voltage, a 10-fold increase in on/off ratio, and superior endurance and uniformity. These findings demonstrate that tuning kinetic parameters has the potential to enhance resistive switching performance, which offers an effective pathway for designing high-performance memory systems.

Improved resistive and synaptic switching performances in bilayer ZrOx/HfOx devices

In this study, we investigated the resistive switching (RS) characteristics of ZrOx/HfOx bilayer-based resistive random-access memory (RRAM) devices. A 1.5-nm-thick HfOx layer was deposited by atomic layer deposition (ALD) between the ZrOx layer and TiN electrode to enhance the RS. Compared to the ZrOx single-layer device, the bilayer device exhibited a lower high resistance state (HRS) current, which improved endurance and reduced energy consumption due to the insulating HfOx layer. In addition, a DC endurance of 300 cycles and strong retention characteristics (10,000 s) were achieved in the bilayer device. Furthermore, the multi-level cell (MLC), potentiation, and depression characteristics were evaluated to demonstrate the suitability of the Ti/ZrOx/HfOx/TiN device for use as a neuromorphic device. With regard to potentiation and depression, various pulse schemes were employed to improve the asymmetric conductance changes for neuromorphic system applications.

Nonvolatile resistive switching in lead-free La2CoMnO6-based memory device

Dense and flat La2CoMnO6 films as the resistive switching functional layer were deposited on n-type Si substrates by sol–gel method. Excellent bipolar resistive switching performance was observed in the Au/La2CoMnO6/Si device for the first time. The high and low resistance states with a ratio of ∼105 could be maintained for more than 1.4 × 104 s and 750 cycles without significant degradation at room temperature. The bipolar resistive switching effect could be sustained within a wide temperature range of 220 K∼300 K. Electrical conduction analysis indicated that the resistive switching behavior in La2CoMnO6 films was primarily controlled by space-charge-limited current mechanism which originated from the change of oxygen vacancies. Density functional theory calculations indicated that the conductive ability of La2CoMnO6 films was promoted with increasing concentration of oxygen vacancies. Moreover, it is found that the modulation of the barrier located at the Au/La2CoMnO6 interface was responsible for the resistive switching under applied bias voltages.

Stable and reliable IGZO resistive switching device with HfAlO x interfacial layer

The performance stability of the resistive switching (RS) is vital for a resistive random-access memory device. Here, by inserting a thin HfAlO x layer between the InGaZnO (IGZO) layer and the bottom Pt electrode, the RS performance in amorphous IGZO memory device is significantly improved. Comparing with a typical metal-insulator-metal structure, the device with HfAlO x layer exhibits lower switching voltages, faster switching speeds, lower switching energy and lower power consumption. As well, the uniformity of switching voltage and resistance state is also improved. Furthermore, the device with HfAlO x layer exhibits long retention time (>104 s at 85 °C) , high on/off ratio and more than 103 cycles of endurance at atmospheric environment. Those substantial improvements in IGZO memory device are attributed to the interface effects with a HfAlO x insertion layer. With such layer, the formation and rupture locations of Ag conductive filaments are better regulated and confined, thus an improved performance stability.