Bipolar Resistive Switching Characteristics Research Articles

Nonvolatile Bipolar Resistive Switching Characteristics of Aluminum Oxide Grown by Thermal Oxidation Processes

Nonvolatile Bipolar Resistive Switching Characteristics of Aluminum Oxide Grown by Thermal Oxidation Processes

High-performance memristor for energy-efficient artificial optoelectronic synapse based on BiVO4 nanosheets

Artificial optoelectronic synapses have drawn extensive attention owing to their ability to combine the optical and electrical responses. Those photosensitive materials that has been reported in memristors have the potential to be adopted in such optoelectronic synapses. Herein, optoelectronic synapses can be achieved based on two-terminal memristors by using two-dimensional (2D) BiVO4 with monoclinic scheelite (m-BiVO4) structure as the memristive layer. The fabricated memristors exhibit bipolar resistive switching (RS) characteristics with stable retention and reliable endurance performance. Furthermore, both electrical and optical synaptic functions can be achieved based on the memristors, such as long-term potentiation (LTP) and depression (LTD) stimulated by the voltages pulses as well as short-term and long-term memory under the light stimulation. More importantly, owing to the LTP and LTD functions with high symmetry, linearity and good repeatability of the LTP/LTD cycles, the artificial neural network can be simulated to achieve image recognition with a high accuracy for handwritten digits. Moreover, both the electrical and optical synapses can be used to emulate the “learning-forgetting” behaviors of human brain. Remarkably, the energy consumption per synaptic event in the optical and electrical modes can be calculated, indicating potential applications in energy-efficient synaptic devices. The m-BiVO4 nanosheets not only demonstrate good non-volatile RS behaviors but also implement energy-efficient optoelectronic synaptic functions, providing a promising strategy for applications in future neuromorphic computing.

Exploring bipolar resistive switching behavior of sprayed BaTiO3 thin films for nonvolatile memory application

The memristive properties of barium titanate (BT) thin films deposited by cost-effective spray pyrolysis technique are explored. The device was configured as Ag/BT/FTO. The electrical measurements unveiled robust bipolar resistive switching (BRS) characteristics in the devices with memory window ∼35. This behavior, attributed to intrinsic defects within BaTiO3, demonstrated the potential of these films for applications in advanced electronic devices like Resistive-Random Access Memory (RRAM). The observed phenomenon arises from the generation of polarized areas within the material, responsive to an applied electric field. Specifically focusing on the memristive aspects, this study indicated promising non-volatile memory performance. All devices undergo the SET process between 0.9 and 1.7 V, and the RESET process takes place between −1.3 to −1.9 V. According to the statistical distribution of SET and RESET voltages, the coefficient of variation (CV) for all devices is less than 18 %. The Ag/BT/FTO memristive device exhibited endurance through 103 cycles of switching, attesting to its reliability. Moreover, the device displayed the capability to maintain stored data for 104 seconds. This establishes the suitability of spray-deposited BaTiO3 thin films for memory-based applications.

Artificial Tactile Sensing Neuron with Tactile Sensing Ability Based on a Chitosan Memristor.

Owing to the highly parallel network structure of the biological neural network and its triggered processing mode, tactile sensory neurons can realize the perception of external signals and the functions of perception, memory, and data processing by adjusting the synaptic weight. In this paper, a piezoresistive pressure sensor is combined with a memristor to design an artificial tactile sensory neuron. The polyurethane sponge sensor has excellent sensitivity and can convert physical stimuli into electrical signals, and the chitosan-based memristor has stable bipolar resistive switching characteristics, allowing further information to be memorized and processed. The neuron can respond to tactile stimuli of different degrees, durations, and frequencies; realize potentiation/depression modulation, paired-pulse facilitation, and spike-timing-dependent plasticity; exhibit spike-rate-dependent plasticity; and store and erase tactile information through memistor state switching, which has great application potential in biological sensing systems.

AlScN/n-GaN Ferroelectric Memristors With Controllable On/Off Ratios and Reversible Bipolar Resistive Switching Characteristics

AlScN/n-GaN Ferroelectric Memristors With Controllable On/Off Ratios and Reversible Bipolar Resistive Switching Characteristics

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

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

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

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

Au decorated ZnO nanostructures for enhanced visible emission and memory applications

Metal/semiconductor nanocomposites present the most versatile way to tune the optical and electrical properties of semiconductors at the nanometer scale. In the present study, Au/ZnO contacts were investigated for their potential applications in optoelectronic devices. There is general agreement that the resonant excitation of surface plasmons (SP) of metal nanoparticles (NP) can couple with the excitons of semiconductors and tune their optical emissions. In this work, the SP and exciton coupling is thoroughly examined using temperature dependent photoluminescence (PL) spectroscopy and Raman spectroscopy in the Au-NPs coated ZnO nanowires. Peculiar to the conventional optical response of Au/ZnO nanostructures at room temperature, PL measurements manifest the suppression of the band edge emissions and enhanced deep level emissions after Au-NPs coating. Raman spectroscopy showed the surface-enhanced Raman scattering (SERS) effect due to field enhancement of the incident light by the SP thus demonstrating potential in ultrasensitive sensing applications. Also, ZnO memristors were fabricated with Au electrodes that exhibited high endurance and longtime retentive bipolar resistive switching characteristics with low SET/RESET voltages. Altogether, present results demonstrate that Au/ZnO composites hold promise for plasmonic based nanoelectronics for memory and neuromorphic applications.

Reset-First and Multibit-Level Resistive-Switching Behavior of Lanthanum Nickel Oxide (LaNiO3-x) Thin Films.

The resistive random-access memory (RRAM) with multi-level storage capability has been considered one of the most promising emerging devices to mimic synaptic behavior and accelerate analog computations. In this study, we investigated the reset-first bipolar resistive switching (RS) and multi-level characteristics of a LaNiO3-x thin film deposited using a reactive magnetron co-sputtering method. Polycrystalline phases of LaNiO3 (LNO), without La2O3 and NiO phases, were observed at similar fractions of Ni and La at a constant partial pressure of oxygen. The relative chemical proportions of Ni3+ and Ni2+ ions in LaNiO3-x indicated that it was an oxygen-deficient LaNiO3-x thin film, exhibiting RS behavior, compared to LNO without Ni2+ ions. The TiN/LaNiO3-x/Pt devices exhibited gradual resistance changes under various DC/AC voltage sweeps and consecutive pulse modes. The nonlinearity values of the conductance, measured via constant-pulse programming, were 0.15 for potentiation and 0.35 for depression, indicating the potential of the as-fabricated devices as analog computing devices. The LaNiO3-x-based device could reach multi-level states without an electroforming step and is a promising candidate for state-of-the-art RS memory and synaptic devices for neuromorphic computing.

Self-Assembled Lanthanum Oxide Nanoflakes by Electrodeposition Technique for Resistive Switching Memory and Artificial Synaptic Devices.

In recent years, many metal oxides have been rigorously studied to be employed as solid electrolytes for resistive switching (RS) devices. Among these solid electrolytes, lanthanum oxide (La2 O3 ) is comparatively less explored for RS applications. Given this, the present work focuses on the electrodeposition of La2 O3 switching layers and the investigation of their RS properties for memory and neuromorphic computing applications. Initially, the electrodeposited La2 O3 switching layers are thoroughly characterized by various analytical techniques. The electrochemical impedance spectroscopy (EIS) and Mott-Schottky techniques are probed to understand the in situ electrodeposition, RS mechanism, and n-type semiconducting nature of the fabricated La2 O3 switching layers. All the fabricated devices exhibit bipolar RS characteristics with excellent endurance and stable retention. Moreover, the device mimics the various bio-synaptic properties such as potentiation-depression, excitatory post-synaptic currents, and paired-pulse facilitation. It is demonstrated that the fabricated devices are non-ideal memristors based on double-valued charge-flux characteristics. The switching variation of the device is studied using the Weibull distribution technique and modeled and predicted by the time series analysis technique. Based on electrical and EIS results, a possible filamentary-based RS mechanism is suggested. The present results assert that La2 O3 is a promising solid electrolyte for memory and brain-inspired applications.

Implementation of Highly Stable Memristive Characteristics in an Organic–Inorganic Hybrid Resistive Switching Layer of Chitosan-Titanium Oxide with Microwave-Assisted Oxidation

This study proposes a high-performance organic–inorganic hybrid memristor for the development of neuromorphic devices in the memristor-based artificial synapse. The memristor consists of a solid polymer electrolyte (SPE) chitosan layer and a titanium oxide (TiOx) layer grown with a low-thermal-budget, microwave-assisted oxidation. The fabricated Ti/SPE–chitosan/TiOx/Pt-structured memristor exhibited steady bipolar resistive switching (BRS) characteristics and demonstrated excellent endurance in 100-cycle repetition tests. Compared to SPE–chitosan memristors without a TiOx layer, the proposed organic–inorganic hybrid memristor demonstrated a higher dynamic range and a higher response to pre-synaptic stimuli such as short-term plasticity via paired-pulse facilitation. The effect of adding the TiOx layer on the BRS properties was examined, and the results showed that the TiOx layer improved the chemical and electrical superiority of the proposed memristor synaptic device. The proposed SPE–chitosan organic–inorganic hybrid memristor also exhibited a stable spike-timing-dependent plasticity, which closely mimics long-term plasticity. The potentiation and depression behaviors that modulate synaptic weights operated stably via repeated spike cycle tests. Therefore, the proposed SPE–chitosan organic–inorganic hybrid memristor is a promising candidate for the development of neuromorphic devices in memristor-based artificial synapses owing to its excellent stability, high dynamic range, and superior response to pre-synaptic stimuli.

Bipolar Resistive Switching Characteristics of Ta/TaxMnyOz/Pt Structure for ReRAM Application with Large Resistance Window

Bipolar Resistive Switching Characteristics of Ta/TaxMnyOz/Pt Structure for ReRAM Application with Large Resistance Window

Effect of annealing upon bipolar resistive switching in amorphous barium titanate (am-BTO) in Ag/am-BTO/ITO capacitor structure

The influence of annealing upon the resistive switching nature of amorphous barium titanate (am-BTO) is systematically investigated. The am-BTO thin film is fabricated on top of ITO coated glass substrate using RF-DC sputtering systems in the form of Ag/am-BTO/ITO dot point geometry. The room temperature electrical characterization shows the bipolar resistive switching characteristics. The resistive switching behaviour is diminished by increasing the temperature from RT to 600 °C. The conduction mechanism analysis is also been carried out. The ohmic and space change limited conduction mechanisms are dominated in lower and higher resistance regions respectively. The schematic representation of the proposed conduction mechanism is also drawn. The restricted movement of silver cations due to the local crystallization of BTO is presumed to be the reason for the observed reduction in switching behaviour.

Resistive switching characteristics of Ag2O/TiO2 bilayer film based memristor

With the increasing importance of artificial intelligence (AI), significant effort has been devoted to the development of memory device that seek to emulate the energy-efficient information storage and processing. In this work, a memristive device with Ag/Ag2O/TiO2/FTO structure was fabricated by the sol-gel method. The as-prepared memristive device exhibits bipolar resistive switching characteristics under direct-current-voltage sweep. In particular, this memristive device with Ag2O/TiO2 layer annealing at 450 ℃ has a low switching voltage after 150 successive cycles. At the same time, the switching window of the device with Ag2O/TiO2 layer annealing at 450 ℃ is obvious, and the switching resistances are stable and easy to distinguish. This device exhibits some obvious advantages of low power consumption, remarkable repeatability, excellent endurance, and stable memory state. As a result, this Ag2O/TiO2 bilayer film based memristive device has great potential to be used as information storage and processor device for AI applications.

Resistive Switching Characteristic of Cu Electrode-Based RRAM Device

The conductive bridge random access memory (CBRAM) device has been widely studied as a promising candidate for next-generation nonvolatile memory applications, where Cu as an electrode plays an important role in the resistive switching (RS) process. However, most studies only use Cu as one electrode, either the top electrode (TE) or the bottom electrode (BE); it is rarely reported that Cu is used as both TE and BE at the same time. In this study, we fabricated CBRAM devices by using Cu as both the TE and BE, and studied the RS characteristic of these devices. With Al2O3 as the switching layer (5~15 nm), the devices showed good bipolar RS characteristics. The endurance of the device could be as high as 106 cycles and the retention time could be as long as 104 s. The Al2O3 thickness influences the bipolar RS characteristic of the devices including the initial resistance, the forming process, endurance, and retention performance. The Cu electrode-based RRAM devices also present negative bias-suppressed complementary resistive switching (CRS) characteristics, which makes it effective to prevent the sneak path current or crosstalk problem in high-density memory array circuits.

The bipolar and self-rectifying resistive switching characteristics of UiO-66 modified with uric acid

The bipolar and self-rectifying resistive switching characteristics of UiO-66 modified with uric acid

Demonstration of high-stable bipolar resistive switching and bio-inspired synaptic characteristics using PEDOT:PSS-based memristor devices

Demonstration of high-stable bipolar resistive switching and bio-inspired synaptic characteristics using PEDOT:PSS-based memristor devices

High-performance non-volatile memory devices from metallomacrocyclic organic micro/nanostructure: Control via molecular manipulation

Here, we report the synthesis of micro/nanostructures of a metal-macrocyclic organic compound, viz, Iron phthalocyanine (FePc) via cost-effective solvothermal method and consequent fabrication of high-performance resistive memory devices from FePc micro/nanorod embedded in poly(methyl methacrylate) (PMMA) matrix. The devices exhibited bipolar and non-volatile resistive switching characteristics. Interestingly, the performances of the devices (On/Off current ratio) improved by several orders of magnitude when an additional buffer layer of PMMA was deposited prior to the deposition of the active film (FePc embedded in PMMA). The variation in thickness of the PMMA buffer layer indicated that at an optimum thickness ca. 15 nm, the best performances were obtained with switching (Set) voltage ca. 1.6 V, On/Off current ratio ∼ 106 and retention ability of more than 10 h. The conduction mechanism has been discussed by linear fitting of the characteristics curves in both low and high resistance states of the device. The analysis lead to the conclusion that trapping/detrapping of charge carriers at the redox and defect sites within the active film (FePc embedded in PMMA) and at the PMMA-FePc/PMMA interface resulted in the resistive switching of the device and a trap induced space charge limited current was found to dominate in the Off- and On-state of the device.

Reconfigurable Low-Voltage Hexagonal Boron Nitride Nonvolatile Switches for Millimeter-Wave Wireless Communications.

Recently, nonvolatile resistive switching memory effects have been actively studied in two-dimensional (2D) transition metal dichalcogenides and boron nitrides to advance future memory and neuromorphic computing applications. Here, we report on radiofrequency (RF) switches utilizing hexagonal boron nitride (h-BN) memristors that afford operation in the millimeter-wave (mmWave) range. Notably, silver (Ag) electrodes to h-BN offer outstanding nonvolatile bipolar resistive switching characteristics with a high ON/OFF switching ratio of 1011 and low switching voltage below 0.34 V. In addition, the switch exhibits a low insertion loss of 0.50 dB and high isolation of 23 dB across the D-band spectrum (110 to 170 GHz). Furthermore, the S21 insertion loss can be tuned through five orders of current compliance magnitude, which increases the application prospects for atomic switches. These results can enable the switch to become a key component for future reconfigurable wireless and 6G communication systems.

Tri-level resistive switching characteristics and conductive mechanism of HfO<sub>2</sub>/NiO<sub>x</sub>/HfO<sub>2</sub>

With the extensive integration of portable computers and smartphones with "Internet of Things" technology, further miniaturization, high reading/writing speed and big storage capacity are required for the new generation of non-volatile memory devices. Compared with traditional charge memory and magnetoresistive memory, resistive random access memory(RRAM) based on transition metal oxides is one of the promising candidates due to its low power consumption, small footprint, high stack ability, fast switching speed and multi-level storage capacity.<br>Inspired by the excellent resistive switching characteristics of NiO and HfO<sub>2</sub>, NiO<sub>x</sub> films were deposited by magnetron sputtering on the Pt<111> layer and the polycrystalline HfO<sub>2</sub> film, respectively. Their microstructures, resistive switching characteristics and conductive mechanisms were studied. X-ray diffractometer data shows the <111> preferred orientation for the NiO<sub>x</sub> film deposited on the Pt<111> layer but the <100> preferred one for the film deposited on the polycrystalline HfO<sub>2</sub> layer. X-ray photoelectron depth profile of Ni2p core level reveals that the NiO<sub>x</sub> film is the mixture of oxygen-deficient NiO and Ni<sub>2</sub>O<sub>3</sub>. NiO<sub>x</sub>(111) films show bipolar resistive switching(RS) characteristics with a clockwise current-voltage(<i>I-V</i>) loop, but its ratio of the high resistance to the low resistance(<i>R</i><sub>H</sub>/<i>R</i><sub>L</sub>) is only~10, and its endurance is also poor. The NiO<sub>x</sub>(200)/HfO<sub>2</sub> stack exhibits bipolar RS characteristics with a counterclockwise <i>I-V</i> loop. The <i>R</i><sub>H</sub>/<i>R</i><sub>L</sub> is greater than 10<sup>4</sup>, the endurance is about 10<sup>4</sup> cycles, and the retention time exceeds 10<sup>4</sup> s. In the initial stage, the HfO<sub>2</sub>/NiO<sub>x</sub>(200)/HfO<sub>2</sub> stack shows similar bi-level RS characteristics with that of the NiO<sub>x</sub>(200)/HfO<sub>2</sub> stack. However, in the middle and the last stages, it's <i>I-V</i> curves gradually evolve into tri-level RS characteristics with a "two-step Set process" in the positive voltage region, showing potential applications in multilevel nonvolatile memory devices and brain-like neural synapses. Its <i>I-V</i> curves in the high and the low resistance states follow the relationship of Ohmic conduction (<i>I</i>∝<i>V</i>), while the <i>I-V</i> curves in the intermediate resistance state are dominated by the space-charge-limited-current mechanism (<i>I</i>∝<i>V</i><sup>2</sup>). The tri-level RS phenomena are attributed to the coexistence of the oxygen-vacancy conductive filaments in the NiO<sub>x</sub>(200) film and the space charge limited current in the upper HfO<sub>2</sub> film.