Bipolar Resistive Switching Behavior Research Articles

Flexible resistive switching device based on air-stable lead-free Cu3SbI6 perovskite film for nonvolatile memory application

Resistive switching (RS) behavior of lead-free rudorffite perovskite Cu3SbI6 is explored for developing high performance flexible resistive switching random access memory (ReRAM) devices. The Cu3SbI6 based devices exhibit reproducible bipolar nonvolatile RS behaviors with low operating voltage (≤±0.6 V), stable endurance (≥400 cycles), and long data retention time (≥104 s). Moreover, the devices fabricated on flexible substrates show good electrical reliability and mechanical stability under different bending angles and consecutive bending cycles (103 times). A computational study method is used to reveal the mechanical stability of the Cu3SbI6 and the RS properties of the memory devices. More importantly, the Cu3SbI6 based devices exhibit no significant changes in RS behaviors after stored in ambient conditions for over 60 days. The results suggest that devices based on all-inorganic lead-free rudorffite perovskite materials have great potential for high performance, stable, and flexible ReRAM.

In-depth understanding of physical mechanism of the gradual switching in AlOxNy-based RRAM as memory and synapse device

This paper reported the Pt/AlOxNy/Ta structure with oxygen scavenging metal Ta as a top electrode in order to achieve excellent data storage and the artificial synaptic function. As a series resistance layer and a thermal enhanced layer, the TaOx interface layer between the resistance switching (RS) layer and the top electrode (TE) can greatly affect the RS characteristics. These effects can be attributed to properties of the interface layer such as thermal and electrical conductivities, suggesting that properties of the interface layer should be carefully and systematically considered if excellent RS characteristics are desirable. Based on the electrical testing and current conduction mechanism analyses, the major factors affecting the bipolar gradual RS behavior can be concluded as the property of the interface layer between the RS layer and TE, the Joule heating caused by current, and the distribution of the electric field on the interface layer.

Robust Resistive Switching Constancy and Quantum Conductance in High-k Dielectric-Based Memristor for Neuromorphic Engineering

For neuromorphic computing and high-density data storage memory, memristive devices have recently gained a lot of interest. So far, memristive devices have suffered from switching parameter instability, such as distortions in resistance values of low- and high-resistance states (LRSs and HRSs), dispersion in working voltage (set and reset voltages), and a small ratio of high and low resistance, among other issues. In this context, interface engineering is a critical technique for addressing the variation issues that obstruct the use of memristive devices. Herein, we engineered a high band gap, low Gibbs free energy Al2O3 interlayer between the HfO2 switching layer and the tantalum oxy-nitride electrode (TaN) bottom electrode to operate as an oxygen reservoir, increasing the resistance ratio between HRS and LRS and enabling multilayer data storage. The Pt/HfO2/Al2O3/TaN memristive device demonstrates analog bipolar resistive switching behavior with a potential ratio of HRS and LRS of > 105 and the ability to store multi-level data with consistent retention and uniformity. On set and reset voltages, statistical analysis is used; the mean values (µ) of set and reset voltages are determined to be − 2.7 V and + 1.9 V, respectively. There is a repeatable durability over DC 1000 cycles, 105 AC cycles, and a retention time of 104 s at room temperature. Quantum conductance was obtained by increasing the reset voltage with step of 0.005 V with delay time of 0.1 s. Memristive device has also displayed synaptic properties like as potentiation/depression and paired-pulse facilitation (PPF). Results show that engineering of interlayer is an effective approach to improve the uniformity, ratio of high and low resistance, and multiple conductance quantization states and paves the way for research into neuromorphic synapses.

A low-power memristor based on 2H–MoTe2 nanosheets with synaptic plasticity and arithmetic functions

Bionic artificial synapses based on 2D transition metal dichalcogenides are comparable to biological synapses due to the unique properties, which are important for building brain-like computing to break the energy and data throughput limit of the von Neumann architecture. In this work, a two-terminal memristor with vertical structure was fabricated by using 2H–MoTe2 nanosheet dispersion. The fabricated memristor based on the Cu/MoTe2/Si structure not only exhibits the stable bipolar nonvolatile resistive switching behavior but also implements the centralized distribution of threshold voltage, and the SET/RESET power can be as low as 0.86 μW/93 nW. Impressively, classical synaptic functions including long-term potentiation/long-term depression, excitatory postsynaptic currents, spike-timing-dependent plasticity, and paired-pulse facilitation were mimicked, which attribute to the formation and rupturing of Cu conductive filaments. Interestingly, the simple arithmetic functions can be operated. Therefore, this work provides a new solution for the development of synaptic devices and neural computing research in the future.

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

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

Enhanced resistive switching characteristics of FeMnO3 resistive random access memory devices with embedding Au nanoparticles

Au nanoparticles (Au NPs) embedded FMO (Au-FMO) thin films were fabricated on Pt/Ti/SiO2/Si substrates by using a chemical solution deposition method. The sandwich structured Pt/Au-FMO/Pt devices exhibit bipolar resistive switching behavior with uniform Set/Reset voltage distribution, stable high and low resistance values, and excellent retention characteristics. The introduction of Au NPs can enhance the local electric field, which greatly reduces the randomness of the generation and fracture of oxygen vacancy conductive filaments. The conduction mechanisms of Pt/Au-FMO/Pt devices in low resistance state and high resistance state can be described by Ohmic conduction and space charge limited current model, respectively. The results show that the Au-FMO films have great potential in the field of resistive random access memory devices.

Spray deposited zinc tungstate thin film for non-volatile memory application

The Ag/ZWO/FTO resistive switching (RS) device was fabricated using the chemical spray pyrolysis method. The crystalline phase, morphology, and atomic composition were characterized effectively through different physicochemical techniques. The fabricated device exhibits bipolar resistive switching behavior with switching voltage below ± 2 V, an HRS/LRS ratio of >10, good endurance of 150 cycles, and retention over 104 s. The β and x63% factors of Weibull distribution suggest the good operational uniformity of the device. The results suggest that ZnWO4-based RRAM can be a potential candidate for non-volatile applications.

Transparent, Flexible, and Low-Operating-Voltage Resistive Switching Memory Based on Al2O3/IZO Multilayer.

In this study, a different number of indium zinc oxide (IZO) interlayers are fabricated into Al2O3‐based transparent resistive switching memory on a transparent indium tin oxide (ITO)/glass substrate at room temperature. Al2O3/IZO multilayer transparent memory has a transmittance of at least 65% in the wavelength range of 400–900 nm. In addition, the Al2O3/IZO multilayer transparent memory can achieve an electroforming voltage that is 35.7% lower than that of ITO/pure‐Al2O3/IZO transparent memory. The fabricated Al2O3/IZO multilayer transparent memory exhibits typical bipolar resistive switching behavior, regardless of the number of IZO interlayers. Also, the fabricated Al2O3/IZO multilayer transparent memory has a low operating voltage within ±1.5 V. In addition, a flexible Al2O3/IZO multilayer transparent memory is fabricated using the same process on ITO‐coated polyethylene terephthalate. The fabricated flexible transparent memory also maintains the resistive switching characteristics during the bending state.

Observation of resistive switching in a graphite/hexagonal boron nitride/graphite heterostructure memristor

With the atomically sharp interface and stable switching channel, van der Waals (vdW) heterostructure memristors have attracted extensive interests for the application of high-density memory and neuromorphic computing. Here, we demonstrate a new type of vdW heterostructure memristor device by sandwiching a single-crystalline h-BN layer between two thin graphites. In such a device, a stable bipolar resistive switching (RS) behavior has been observed for the first time. We also characterize their switching performance, and observe an on/off ratio of >10 3 and a minimum RESET voltage variation coefficient of 3.81%. Our work underscores the potential of 2D materials and vdW heterostructures for emerging memory and neuromorphic applications.

Resistive switching properties of monolayer h-BN atomristors with different electrodes

Resistive switching properties based on molecular beam epitaxy-grown monolayer hexagonal boron nitride (h-BN) atomristors are studied by using metal insulator metal configurations with different electrode materials. Au/monolayer h-BN/Ni devices demonstrate a forming-free bipolar resistive switching (BRS) behavior, a good endurance with up to 97 cycles at a high compliance current of 100 mA, an average on/off ratio of 103, and a low set/reset voltage variability. Metal/monolayer h-BN/graphite/Co devices exhibit self-compliant current BRS characteristics. Both metal/h-BN/Ni and metal/h-BN/graphite/Co devices show the coexistence of BRS, unipolar resistive switching (URS), and nonvolatile threshold switching (TH) modes. The formation of conductive filaments is attributed to the diffusion and trapping of metal ions on the defect sites driven by the electric field, while the rupture is driven by the electric field in BRS and by Joule heating in URS and TH modes.

Thickness dependent resistive switching behaviors in Ta2O5 layer at low temperature: Towards flexible, invisible, cryo-electronic applications in aerospace

The role of Ta2O5 resistive switching (RS) layer thickness on transparent resistive random-access memories (TRRAMs) is systematically investigated. Ta2O5 TRRAMs (t-TRRAMs) exhibits not only high optical transmittance (82%) in the visible region but also bipolar resistive switching behavior with RON/ROFF ratio of ≈103, SET voltage of (0.37 ± 0.08)V, RESET voltage of -(2.83 ± 0.42)V, good endurance of ≈103 cycles and retention over 104s at room temperature (RT) as well as 80 °C. The temperature-dependent RS properties for t-TRRAMs are experimentally validated from low temperature (150 K) to elevated temperature (333 K). Furthermore, t-TRRAMs are implemented on ITO-coated flexible polyethylene terephthalate (PET) substrates. The flexible t-TRRAMs demonstrate RON/ROFF ratio of ≈102, reasonable endurance of ≈500 cycles, and retention over 104s at RT. The experimental results indicate that t-TRRAMs can be a potential candidate for flexible, invisible, cryo-electronic applications.

Resistive switching and photovoltaic response characteristics for the BaTiO3/Nb:SrTiO3 heterostructure

Recently, perovskite compounds with ABX3 structures have been attracting increasing attention because of their excellent properties and their potential for applications in fields such as optoelectronics and memory devices. In this Letter, we introduce a BaTiO3/Nb:SrTiO3 (BTO/NSTO) heterostructure that displays both resistive switching and photovoltaic response characteristics. As a dual-function device, our heterostructure device not only exhibits bipolar resistive switching behavior with a switching ratio of up to 103 without any forming process but also shows a tunable photovoltage effect with an open-circuit voltage (Voc) of approximately 0.38 V. In addition, a high-resistance state and a low-resistance state of the device can be modulated by light illumination. This photo-modulation mechanism is revealed and shows that resistive switching can be attributed to migration of photogenerated carriers and charge trapping/detrapping caused by ferroelectric polarization reversal, which changes depletion layer characteristics at the BTO/NSTO interface. This work may help to provide an understanding of multifunctional characteristics of the BTO/NSTO heterostructure and will pave the way toward practical applications of this heterostructure in memory and optoelectronic devices.

Bipolar resistive switching in Ag/VO2(B)/SiOx/n++Si RRAM

Non-volatile resistive random-access memory (RRAM) is being promoted as a possible alternative to flash memory, however the optimal material system and sophisticated fabrication techniques hinder its utilization in practical routes. Here, we demonstrate the direct fabrication of metal/oxides/semiconductor (MOS) structured Ag/VO2(B)/SiOx/n++Si RRAM via drop-coating process, in which bipolar resistive switching behavior was obtained and investigated systematically. The RRAM devices exhibit good cycle-to-cycle endurance (>30 cycles) and high on/off ratio (>60). The switching mechanism is proposed to form Ag conducting filaments via VO2(B) nanorods’ guide by comparing the resistive switching behavior of Ag/SiOx/n++Si, Ag/VO2(B)/n++Si, Ag/VO2(B)/SiOx/n++Si devices and the corresponding SEM images before and after the application of electric field, which is confirmed by introducing NaCl barrier layer in Ag/VO2(B)-NaCl/SiOx/n++Si devices. The present study may pave a convenient route for fabricating the ultrahigh density resistive memory devices without the aid of complex fabrication techniques, as well as provide a new potential material system for RRAM.

Resistive switching properties for fluorine doped titania fabricated using atomic layer deposition

This study demonstrates a new resistive switching material, F-doped TiO2 (F:TiO2), fabricated by atomic layer deposition (ALD) with an in-house fluorine source for resistive random access memory (RRAM) devices. Controlling oxygen vacancies is required since RRAM uses resistive switching (RS) characteristics by redistributing oxygen ions in oxide, and poor oxygen defect control has been shown to significantly reduce RRAM reliability. Therefore, this study designed an F based RRAM device using fluorine anions rather than oxygen defect for the main agent of RS behavior. We developed the F:TiO2 RRAM material using a novel in situ doping method in ALD and investigated its RS behaviors. The Pt/F:TiO2/Pt device exhibited forming-less bipolar RS and self-rectifying behavior by fluorine anion migration, effectively reducing the sneak current in crossbar array architecture RRAM. The doped fluorine passivated and reduced oxygen related defects in TiO2, confirmed by x-ray photoelectron spectroscopy analysis. Adopting the F-based RS material by ALD provides a viable candidate for high reliability RRAM.

Resistive switching and conductance quantization in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)-based resistive random access memory device with printable top electrodes

In this study, we present the fabrication of a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)-based resistive random access memory (RRAM) device using a fully vacuum-free and solution-processed fabrication method, realized using a printable top electrode. Three different printable electrodes, namely Ag epoxy, ethylene glycol(EG)-treated PEDOT:PSS, and dimethyl sulfoxide(DMSO)-treated PEDOT:PSS, were used as the top electrode of the RRAM device. Different top electrodes exhibited different switching behaviors as volatile or nonvolatile memory devices. Accordingly, the RRAM device with the Ag epoxy top electrode demonstrated nonvolatile bipolar switching with a quantization effect in the RESET process and multilevel switching. Meanwhile, the RRAM device with the EG-treated PEDOT:PSS electrode exhibited abnormal bipolar resistive switching behavior. Lastly, the RRAM device with the DMSO-treated PEDOT:PSS electrode exhibited volatile switching for the highest stability of up to 500 cycles.

Bipolar resistive switching properties of TiO x /graphene oxide doped PVP based bilayer ReRAM

In this paper, firstly, some recently explored promising materials and processes for resistive random access memory (ReRAM) devices with bipolar switching mechanism along with their performance are discussed. Further, resistive switching behaviour of TiO x /graphene oxide (GO):poly(4-vinylphenol) (PVP) based bilayer in ReRAM devices is demonstrated. It was found that bipolar resistive switching behaviour is significantly enhanced by embedding 2D material such as GO in the organic polymer acting as switching layer. ReRAM devices with Ag/PVP:GO/TiO x /fluorine doped tin oxide (FTO) structure exhibited high ON/OFF current ratio (>103), low voltage operation, and high retention time. Bipolar resistive switching from these engineered active layers will have great potential for future large area and sustainable electronics.

Optimizing endurance performance of Ga2O3 random resistive access memories by altering oxygen vacancy content

In this work, we propose an effective way to improve the endurance performance of Ga 2 O 3 resistive random access memories by doping ZnO. Excellent bipolar resistive switching behaviors have been observed in atomic-layer-deposited ZnO-doped Ga 2 O 3 RRAMs, which exhibit large memory windows over 10 3 and retention time up to 10 4 . Bipolar resistive switching behaviors can be explained by the formation or rupture of conductive filaments composed of Ag atoms and oxygen vacancies. Current – voltage curves suggest Ohmic conductance of the low resistance states, while the conductive mechanism of the high resistance states corresponds to the trap-assisted space charge limited conduction. Furthermore, the reason why the endurance performance of ZnO-doped Ga 2 O 3 RRAMs is better than pure Ga 2 O 3 RRAMs is analyzed.

Sol-Gel Processed ZrO2 Based Forming-Free Resistive Switching Memory Devices

In this work, we fabricated ZrO2 based resistive random access memory by sol-gel spin coating technique and investigated its structural, optical and resistive switching properties. The X-ray diffraction pattern revealed that 400 °C annealed ZrO2 thin film has tetragonal structure. The optical band gap value of ZrO2 thin film obtained was 5.51 eV. The resistive switching behaviour of W/ZrO2/ITO capacitor like structure was studied. It was found that no initial electroforming process required for the device. The fabricated devices show a self-compliance bipolar resistive switching behaviour and have high on off ratio (>102). Our result suggests that solution processed ZrO2 has great potential to develop transparent and flexible resistive random access memory devices.

Forming‐Free Pt/Ti/AlOx/CeOx/Pt Multilayer Memristors with Multistate and Synaptic Characteristics

Due to their unique electrical performance and simple structure, memristors exhibit excellent application prospects for future information technology. In this work, we fabricated Pt/Ti/AlOx/CeOx/Pt memristors demonstrating electroforming‐free bipolar resistive switching behavior with low operating voltage (−1 to 1 V), stable endurance, and retention. Space‐charge limited conduction (SCLC) as well as the formation and rupture of conductive filaments are responsible for the resistive switching behavior. Increasing the magnitude of the RESET voltage could generate multistate resistive switching. We studied the synaptic characteristics of the device by obtaining multilevel conductance states and investigating the relationship between the device resistance, pulse amplitude, pulse width, and pulse number. By applying programmed pre and postsynaptic spiking pulses, spike‐timing dependent plasticity was observed. This study shows that the device is suitable for multivalue storage and can be used as an electronic synapse device in artificial neural networks.

3D-structured mesoporous silica memristors for neuromorphic switching and reservoir computing.

Memristors are emerging as promising candidates for practical application in reservoir computing systems that are capable of temporal information processing. Here, we experimentally implement a physical reservoir computing system using resistive memristors based on three-dimensional (3D)-structured mesoporous silica (mSiO2) thin films fabricated by a low cost, fast and vacuum-free sol-gel technique. The in situ learning capability and a classification accuracy of 100% on a standard machine learning dataset are experimentally demonstrated. The volatile (temporal) resistive switching in diffusive memristors arises from the formation and subsequent spontaneous rupture of conductive filaments via diffusion of Ag species within the 3D-structured nanopores of the mSiO2 thin film. Besides volatile switching, the devices also exhibit a bipolar non-volatile resistive switching behavior when the devices are operated at a higher compliance current level. The implementation of mSiO2 thin films opens the route to fabricate a simple and low cost dynamic memristor with a temporal information process functionality, which is essential for neuromorphic computing applications.