Resistive Switching Parameters Research Articles

Influence of stop and gate voltage on resistive switching of 1T1R HfO2-based memristors, a modeling and variability analysis

Memristive devices, particularly resistive random access memory (RRAM) cells based on hafnium oxide (HfO₂) dielectrics, exhibit promising characteristics for a wide range of applications. In spite of their potential, issues related to intrinsic variability and the need for precise simulation tools and modeling methods remain a medium-term hurdle. This study addresses these challenges by investigating the resistive switching (RS) behavior of different 1T1R HfO₂-based memristive devices under various experimental conditions. Through a comprehensive experimental analysis, we extract RS parameters using different numerical techniques to understand the cycle-to-cycle (C2C) and device-to-device (D2D) variability. Additionally, we employ advanced simulation methodologies, including circuit breaker-based 3D simulation, to shed light on our experimental findings and provide a theoretical framework to disentangle the switching phenomena. Our results offer valuable insights into the RS mechanisms and variability, contributing to the improvement of robust parameter extraction methods, which are essential for the industrial application of memristive devices.

Exploring statistical approaches for accessing the reliability of Y2O3-based memristive devices

Memristive devices have emerged as promising alternatives to traditional complementary metal-oxide semiconductor (CMOS)-based circuits in the field of neuromorphic systems. These two-terminal electronic devices, known for their non-volatile memory properties, can emulate synaptic behavior within artificial neural networks, offering remarkable advantages, including scalability, energy efficiency, rapid operation, compact size, and ease of fabrication. They hold the potential to serve as fundamental components for artificial neurons, revolutionizing neuromorphic computing systems by closely mimicking biological neurons. However, the integration of resistive random-access memory (RRAM) into commercial production faces challenges due to substantial variations in resistive switching (RS) parameters, which include cycle-to-cycle (C2C) and device-to-device (D2D) fluctuations. These variations are rooted in the stochastic nature of RS, linked to physical mechanisms like diffusion and redox reactions. Nonetheless, limitations exist in the current analytical approaches, emphasizing the need for more standardized tools to assess memristive device reliability consistently. Weibull distribution is widely used to analyze RRAM variability and many further studies are based on it. However, this distribution may not work well for some memristive devices. In such cases, one can use other statistical distributions available in the literature. In the present work, statistical distributions, namely Weibull, Exponential, Log-Normal, Gamma, and Logistic distributions, are employed to scrutinize memristive devices device parameters, shedding light on their performance and reliability. Also, analytical methods namely maximum likelihood estimates for parameter estimation and Kolmogorov-Smirnov test for assessing goodness of fit of the distributions are used. This study aims to provide an approach with a deeper understanding of memristive device parameters and analysis techniques.

Cycle-to-cycle variability analysis of Ti/Al2O3-based memristors

In this work, an experimental analysis of the resistive switching behavior of TiN/Ti/Al2O3/W memristors is presented. The main focus is on the analysis of the variability of the key parameters during long series of cycles, using both sweep and pulsed voltage measurement sequences. In addition, the correlation of the resistive switching parameters between subsequent cycles has been investigated. The results demonstrate that memristors based on Ti/Al2O3 exhibit a low cycle-to-cycle variability between consecutive cycles, indicating their potential use for emerging applications.

Polyacrylonitrile Passivation for Enhancing the Optoelectronic Switching Performance of Halide Perovskite Memristor for Image Boolean Logic Applications.

For the CH3NH3PbI3-based optoelectronic memristor, the high ion-migration randomness induces high fluctuation in the resistive switching (RS) parameters. Grain boundaries (GBs) are well known as the ion-migration sites due to their low energy barrier. Herein, a polyacrylonitrile (PAN) passivation method is developed to reduce GBs of the CH3NH3PbI3 film and improve the switching uniformity of the memristor. The crystal grain size of CH3NH3PbI3 increases with the addition of PAN, and the corresponding number of GBs is consequently reduced. The fluctuations of the RS parameters of the memristor device are significantly reduced. With the memristor, nonvolatile image sensing, image memory, and image Boolean operations are demonstrated. This work proposes a strategy for developing high-performance CH3NH3PbI3 optoelectronic memristors.

Effect of TiW blocking layer and temperature annealing on resistive switching parameters of Hafnium oxide based CBRAM device

An approach for enhancing the characteristics of resistive switching in the crystalline Hafnium oxide-based CBRAM (Conductive Bridging Resistive Switching Memory) device is reported in this article. The crystalline Hafnium oxide resistive switching layer and the TiW blocking layer are beneficial for controlling filament growth. Improved resistive parameters, including stability and resistance distribution, were successfully demonstrated in Cu/TiW/annealed-HfO2/Pt devices compared to Cu/HfO2/Pt-based devices. Moreover, the proposed bipolar device demonstrates improved memory performance, such as good retention characteristics (>104 s) and a high ON/OFF resistance ratio.

Anatomy of resistive switching behavior in titanium oxide based RRAM device

Resistive random access memory (RRAM) devices based on binary transition metal oxides and the application for nonvolatile memory devices are becoming an area of extensive concern. The physical understanding of resistive switching is crucial for RRAM development. In this paper, both experiments and simulated dynamic formation and rupture processes of oxygen vacancy (VO) conductive filament (CF) channels in titanium oxide based RRAM devices are presented. Compared with the Al/TiO2.1/Al device with higher oxygen content, the Al/TiO1.6/Al device shows a lower forming voltage. However, little dependence on oxygen content in TiOx film is shown for other resistive switching parameters, including high resistance state resistance, low resistance state resistance, set voltage, and reset voltage. A numerical physics model is presented to relate the resistive switching behavior with the evolution CF channels in terms of VO morphology and I−V characteristics.

Emulating synaptic plasticity and resistive switching characteristics through amorphous Ta2O5 embedded layer for neuromorphic computing

Memristors with controllable resistive switching (RS) characteristics gain significant attention for neuromorphic computing applications in high-density memory and artificial synapses. Herein, we present the consequence of an amorphous Ta2O5 embedded layer on RS and synaptic characteristics of ZrO2 memristor. Structural and electronic properties of the memristor without and with-Ta2O5 are exemplified by x-ray diffraction (XRD) and x-ray photoemission spectroscopy (XPS) measurements. Memristor with-Ta2O5 exhibits excellent performance in RS parameters such as lower forming/SET-voltage, improved uniformity of switching cycling, admirable pulse endurance (104), and long retention time (104 s). Moreover, multilevel storage capability is achieved through limiting the current compliance in SET-operation or stop-voltages in RESET-operation. Likewise, diverse synaptic characteristics such as long-term potentiation (LTP), long-term depression (LTD), spike-rate-dependent plasticity (SRDP), paired-pulse facilitation (PPF), and post-tetanic potentiation (PTP), spike-timing-dependent plasticity (STDP) are effectively mimicked, which is regarded as an imperative learning regime of biological synapses. Owing to improved linearity of LTP/LTD behaviors in memristor with-Ta2O5, a solid recognition rate (~85%) is achieved for pattern recognition with the modified national institute of standards and technology database (MNIST) handwritten numbers. Memristor with embedded ~2 nm Ta2O5 barrier layer shows significant potential applications in high-performance multilevel data storage and neuromorphic computing systems.

Rapid microwave annealing of CH3NH3PbI3 with controllable crystallization for enhancing the resistive-switching performance

High switching fluctuation induced by the random formation and rupture of conductive filaments (CFs) is a critical issue for the development of organic-inorganic perovskite-based resistive switching (RS) memory devices. In this study, a rapid microwave-annealing method is developed to reduce grain boundaries (GBs) of CH3NH3PbI3 (MAPbI3) film and improve the switching reliability of the Au/MAPbI3/FTO device. The crystal grain size of MAPbI3 is increased and the corresponding GBs number is reduced with microwave irradiation time ranging from 40 to 120 s. In the optimized case, the dispersion of the RS parameters of the Au/MAPbI3/FTO cell is greatly reduced. Specifically, the fluctuations of the high/low resistance states and SET/RESET voltages dropped from 70.4%/69.5% and 40.5%/40.3% to 20.1%/26.7% and 16.0%/11.9%, respectively. The device can be operated with reduced compliance current. These results demonstrate that reducing the number of GBs is a feasible strategy to reduce the randomness of the CFs, and thus achieve more stable RS performance in MAPbI3-based memory devices.

Structure‐Dependent Influence of Moisture on Resistive Switching Behavior of ZnO Thin Films

AbstractResistive switching mechanisms underlying memristive devices are widely investigated, and the importance as well as influence of ambient conditions on the electrical performances of memristive cells are already recognized. However, detailed understanding of the ambient effect on the switching mechanism still remains a challenge. This work presents an experimental investigation on the effect of moisture on resistive switching performances of ZnO‐based electrochemical metallization memory cells. ZnO thin films are grown by chemical vapor deposition (CVD) and radio frequency sputtering. Water molecules are observed to influence electrical resistance of ZnO by affecting the electronic conduction mechanism and by providing additional species for ionic conduction. By influencing dissolution and migration of ionic species underlying resistive switching events, moisture is reported to tune resistive switching parameters. In particular, the presence of H2O is responsible for a decrease of the forming and SET voltages and an increase of the ON/OFF resistance ratio in both CVD and sputtered films. The effect of moisture on resistive switching performance is found to be more pronounced in case of sputtered films where the reduced grain size is responsible for an increased adsorption of water molecules and an increased amount of possible pathways for ion migration.

First principles investigation of oxygen vacancies filaments in polymorphic Titania and their role in memristor's applications

• Basic memristor characteristics are investigated for oxygen vacancies filaments in polymorphic Titania. • The electronic modification subsequently with the creation of the oxygen vacancies in TiO 2 phases have been investigated using density functional theory in depth which could support underlying mechanism of resistive switching . • Integrated charge density plots depicted charge transfer mechanism of three crystalline phases of TiO 2 . • The conductivity of the phases increased with increasing the number of oxygen vacancies; and eventually resulted that the considered phase opted the low resistance state. • From iso-surface charge density, integrated charge density and formation energy calculations, it is predicted that brookite phase of TiO 2 having 3V o is more stable and more conductive for various applications. Inconsistency of resistive switching parameters in memristors is a major challenge in the development of memory devices. These variability issues can be resolved by using materials having capability of easily growing conducting filaments and less value of oxygen vacancy formation energy (OVFE). In this first principle study, device to device variability by the electronic modification subsequently with the creation of the oxygen vacancies in TiO 2 phases have been investigated using density functional theory. The lattice constants, OVFE, density of states (DOS), partial density of states (PDOS), iso-surface charge density and integrated charge density are calculated to understand the structural and electronic properties of polytype TiO 2 with single-, di- and tri-oxygen vacancy (V o ) at atomistic level. It is found that by introducing the V o s, defect states are formed within the band gap, which caused to increase the conductivity of crystalline phases of TiO 2 . The conductivity of the phases increased with increasing number of V o s resulting in low resistance state of the opted phase. Existence of various stages of CFs and formation energy at various concentration of V o s predicts the implementation of constructive role of noise to enhance the efficiency and stability of the Titania based memristors. On the basis of easily growing conducing filaments having higher concentration of V o s with lesser OVFE, it is predicted that brookite phase of TiO 2 having 3V o s is more suitable in overcoming inconsistency issues related to resistive switching in low power consuming memristors devices.

Optical erasable bipolar resistive switching on TiO2 film in nanoscale

Controlling the resistive switching parameters by using external fields is of great importance in the application of the resistive memory devices. In this work, we investigate the effect of light illumination and oxygen atmosphere on the resistive switching of the anatase phase polycrystalline TiO2 thin film using the in-situ conductive atomic force microscopy and Kelvin probe force microscopy. A forming free bipolar resistive switching effect with ON/OFF ratio over 104 was achieved in nanoscale uniformly on the film. The conduction characteristics can be changed from the non-rectifying behavior in vacuum to the Schottky rectifying behavior in oxygen gas with nearly the same ON/OFF ratio. The reversible surface potential shift accompanied by the resistance switching was also observed. Furthermore, the resistance states and the surface potential contrast can be erased by 395 nm near-UV illumination, demonstrating a good optical erasing performance of the device. Combining the surface potential shift and the response to the illumination and oxygen gas, a charge trapping/detrapping mechanism was confirmed to account for the observed switching behavior. These results provide a new way to fabricate the controllable and optical erasable resistive switching devices in nanoscale.

Stochastic resonance in a metal-oxide memristive device

Abstract The stochastic resonance phenomenon has been studied experimentally and theoretically for a state-of-art metal-oxide memristive device based on yttria-stabilized zirconium dioxide and tantalum pentoxide, which exhibits bipolar filamentary resistive switching of anionic type. The effect of white Gaussian noise superimposed on the sub-threshold sinusoidal driving signal is analyzed through the time series statistics of the resistive switching parameters, the spectral response to a periodic perturbation and the signal-to-noise ratio at the output of the nonlinear system. The stabilized resistive switching and the increased memristance response are revealed in the observed regularities at an optimal noise intensity corresponding to the stochastic resonance phenomenon and interpreted using a stochastic memristor model taking into account an external noise source added to the control voltage. The obtained results clearly show that noise and fluctuations can play a constructive role in nonlinear memristive systems far from equilibrium.

Bipolar resistive switching properties of titanium dioxide thin films deposited by different techniques

A comparative study of bipolar resistive switching in thin films of titanium dioxide, fabricated by different techniques, was carried out by analysis of current-voltage characteristics (I-V). For this purpose metal-insulator-metal (MIM) structures were formed with 60-nm-thick titanium dioxide layer deposited by atomic layer deposition (ALD) or RF magnetron sputtering. Based on the analysis of resistance switching characteristics, it was found that the deposition technique of titanium dioxide thin films influences the reproducibility of high-resistance state (HRS) at cycling measurements, the on-resistance (low resistance state)/off-resistance (HRS) ratio, the average values of SET [switching the resistance from a HRS to a low resistance state (LRS)] and RESET [switching the resistance from LRS to HRS] voltages and the number of resistive switching cycles. The results of study of the thin film topography performed by atomic force microscopy (AFM) suggest that the difference in resistive switching parameters could be caused by structural properties of titanium dioxide layers deposited by different techniques.

Impact of the Atomic Layer-Deposited Ru Electrode Surface Morphology on Resistive Switching Properties of TaOx-Based Memory Structures.

Resistive switching (RS) device behavior is highly dependent on both insulator and electrode material properties. In particular, the bottom electrode (BE) surface morphology can strongly affect RS characteristics. In this work, Ru films with different thicknesses grown on a TiN layer by radical-enhanced atomic layer deposition (REALD) are used as an inert BE in TaOx-based RS structures. The REALD Ru surface roughness is found to increase by more than 1 order of magnitude with the increase in the reaction cycle number. Simultaneously, a wide range of RS parameters, such as switching voltage, resistance both in low and high resistance states, endurance, and so forth, monotonically change. A simplified model is proposed to explain the linkage between RS properties and roughness of the Ru surface. The field distribution was simulated based on the observed surface morphologies, and the resulting conducting filament formation was anticipated based on the local field enhancement. Conductive atomic force microscopy confirmed the theoretical expectations.

Annealing effects on resistive switching of IGZO-based CBRAM devices

In this study, the impact of post-oxide deposition annealing on performance of IGZO-based conductive-bridging random access memory (CBRAM) is reported. It is found that besides the distinct reduction in resistive switching parameters of SET/RESET voltages, their dispersions, and the resistance ratio of high-resistance state to low-resistance state can be improved after N2 annealing. The annealing effects on enhancing of the resistive switching properties are investigated by x-ray photoelectron spectra. It can be considered that the formation of the filament is better controlled by the increase of oxygen vacancies in the switching layer, which is the main reason for the improvement of resistive switching characteristics.

Physically transient random number generators based on flexible carbon nanotube composite threshold switching

The resistive switching memories are in prosperity development on account of its simple structure and high performance. A primary problem of resistive switching memory reliability is discrete and random distribution of resistive switching parameters, which limits greatly the possible range of its digital memory application on account of uniformity of resistance parameters is poor and the distribution range is too large. But, from the other side, these random parameter distributions are eable be used to complete some computing tasks. Here, a random number generation is demonstrated with stochastic variation of Vset in a flexible threshold switching device by using the carbon nanotube and polyvinyl alcohol composite materials. Two reading voltages was applied to the two threshold switching devices, the electric potential of Vcin randomized either positive or negative in accordance with the cycle to cycle evolution of two threshold switching devices by the control of the voltage divider, which in return comes about a random bitstream after passing by the comparer. As well as, its transient characteristics have been illustrated for data security appilcation.

Impact of resistive switching parameters on resistive random access memory crossbar arrays

Sneak current issue of RRAM-based crossbar array is one of the biggest hindrances for high-density memory application. The integration of an addition selector to each cell is one of the most familiar solutions to avoid this undesired cross-talk issue, and resistive switching parameters would affect on the storage density. This paper investigates the potential impact of different resistive switching parameters on crossbar arrays with one-diode one-resistor (1D1R) and one-selector one-resistor (1S1R) architectures. Results indicate that 1S1R architecture is a more scalable technology for high-density crossbar array than 1D1R, and the storage density of 1D1R- and 1S1R-based crossbar array shows little dependence on resistance values of high-resistance state and low-resistance state, which gives a guideline for choosing appropriate selectors for RRAM crossbar array with specific parameters.

Impact of Interfacial SiO2 on Dual Ion Beam Sputtered Y2O3-Based Memristive System

In this article, the effect of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer is demonstrated on dual ion beam sputtered yttria-based memristive devices for the first time. It is found that the effect of thickening of SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer is extremely detrimental for resistive switching (RS) parameters such as endurance and uniformity of current-voltage characteristics. SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interfacial layer causes the growth of nano stalagmite in the yttria layer. This interfacial layer is also responsible for the origin of pseudo bipolarity in RS characteristics and early failure of the device during endurance testing. The thickness of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer has a positive correlation with deposition temperature and oxygen partial pressure. It is found that the deposition temperature of 300°C and a mixture of Ar:O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with a ratio of 2:3 shows the best RS characteristics.

Oxygen annealing effect on resistive switching characteristics of multilayer CeO2/Al/CeO2 resistive random-access memory

Cerium oxide-based memristors have been extensively studied because of their compatibility with CMOS technology. Yet, inconsistency of resistive switching parameters is one of the main contests in development of nonvolatile memory for commercialization. Owing to filamentary nature of the resistive switching devices, variability of the resistive switching characteristics can be reduced by doping, where conductive filaments can easily grow due to reduction in the formation energy of oxygen vacancies. In this work, multilayer CeO2/Al/CeO2 films were prepared through radio-frequency (rf) sputtering at room temperature to study the effect of oxygen annealing on the resistive switching characteristics. Device with CeO2/Al/CeO2 multilayer structure after annealing exhibits reduction of defects and improved switching endurance, good data retention, and uniformity in operational parameters. The resistive switching characteristics have been simulated using space charge limited conduction and Schottky emission at high field region of the high resistance state, which is well fitted by linear curve fitting analysis. Improvement in the switching characteristics revealed that Al charge trapping layer has diffused into the CeO2 matrix, which might have resulted in lower density of oxygen vacancies due to oxygen annealing. Experimental I–V analysis indicate that oxygen annealing is an effective approach to enhance the switching characteristics of RRAM devices.

Stretchable HfO2-Based Resistive Switching Memory Using the Wavy Structured Design

In this letter, we report a stretchable HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based resistive switching memory device utilizing the wavy structured strategy. The fabricated Cu/HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Au device shows reliable and reversible resistive switching behaviors up to a stretching strain of 20%. After being released, the reproducible memory characteristics of the device can still be maintained. The statistical resistive switching parameters under various stretching strains in the range from 0% to 20% are counted, which exhibit a large OFF/ON resistance ratio (10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), low operation voltage (2 V), good endurance and retention (10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> s), demonstrating the good and reliable stretchable memory characteristics. Moreover, the device-to-device distributions are carried out in these stretched states, further validating the device robustness on stretching strains. Our results show a promising approach to achieve the stretchable memory by rendering inorganic-based resistive switching devices with the wavy structure, which extends rigid and brittle memory towards future highly flexible, even stretchable data storage and computing.