Bipolar Resistive Switching Behavior Research Articles

Facile synthesis of MXene−Polyvinyl alcohol hybrid material for robust flexible memristor

MXenes are emerging two-dimensional (2D) nanomaterials composed of transition metal carbides/nitrides/carbonitrides with several atomic layers. However, due to the analogous metallic conductivity, their development in the field of electronic devices is restricted. Recently, various etching methods of MXenes lead to the surface terminals containing different functional groups, which provides opportunities for further modification of MXene nanosheets and makes it possible to apply them in the field of electronic memristors. At present, there are few researches about memristors on the basis of MXene-polymer hybrid materials. Here, we synthesize Ti3C2Tx-MXenes and adjust their content in an insulating polyvinyl alcohol (PVA) polymer for triggering memristive performance, which affords outstanding bipolar resistive switching behavior. The memristor exhibits the characteristics of low operating voltage, long retention time, high flexibility, and acceptable mechanical stability. In order to examine the switching mechanism of the device, the charge transport model simulation is implemented, which indicates that charge trapping effect is responsible for the non-volatile memristor performance of Ti3C2Tx-PVA hybrid material. This work provides a simple strategy for preparing MXene-polymer hybrid materials and broadens the prospects of 2D MXenes in the field of non-volatile memory applications.

Anti-bacterial and transparent allantoin biomaterial-based biocomposite for non-volatile memory and brain-inspired computing applications

The allantoin biomaterial-based biocomposite was utilized to fabricate resistive switching (RS) devices for non-volatile memory and brain-inspired computing applications. The polymeric phase, surface morphology, and purity of biomaterial were characterized using different analytical tools. The allantoin biofilm shows anti-bacterial and transparent properties, therefore, it can be useful for wearable electronics. Novel allantoin biomaterial-based composite device exhibits forming-free bipolar resistive switching behavior with low SET (+0.50 V) and RESET (−1.34 V) voltages, good endurance (3 × 103 cycles), and memory retention properties (103 s). Additionally, the device mimics various bio-synaptic properties such as excitatory postsynaptic current, paired-pulse facilitation, and paired-pulse depression.

Study of Growth and Properties of Electrodeposited Sodium Iron Hexacyanoferrate Films.

Sodium iron hexacyanoferrate (NaFeHCF) films were electrodeposited on Au/Cr/Si for the study of growth behavior and physical properties. The NaFeHCF films were studied by different analytical methods to prove the chemical composition, morphology and crystal structure. The grains of the film grow with a cubic structure with an average lattice parameter of 10.10 Å and the preferential growth direction along the [111] direction of the cubic cell. The films show a repeatable bipolar resistive switching behavior accompanied by high current changes (up to a factor of ~105). The different resistive states in the materials are dominated by ohmic conduction.

Existence of bipolar resistive switching with self-rectifying behavior in a p-CuCrO2/n-Si heterostructure

The resistive random access memory with self-rectifying behavior is one of the most effective to suppress the crosstalk current problem in crossbar array architectures. In this study, a p-type delafossite CuCrO2 thin film is fabricated on an n-type silicon (n-Si) substrate, and the resistive switching (RS) behavior of the Au/CuCrO2/n-Si device is investigated in detail. The heterostructure exhibits repeatable bipolar RS with self-rectifying behavior. The bipolar RS behavior can be attributed to the trapping/detrapping of charge carriers in oxygen vacancies at the p-CuCrO2/n-Si interface. The current-voltage characteristics indicate that the self-rectifying behavior in the low resistance state is derived from the Schottky-like barrier at the interface of p-CuCrO2/n-Si. These results provide a potential utilization of resistive random access memory with self-rectifying behavior in p-type delafossite-based heterostructures.

A synaptic memristor based on natural organic honey with neural facilitation

Neural facilitation is an essential activity-dependent synaptic plasticity in most chemically transmitting synapses. Emerging artificial synaptic devices need to be capable of emulating this function in order to be used in brain-inspired neuromorphic computing systems. In this paper, neural facilitation in natural organic honey based synaptic memristor was investigated. The memristive layer was fabricated by commercially purchased honey via a solution-based process and sandwiched in between Al top electrode and ITO bottom electrode. Two process conditions, 90 °C/8 h and 140 °C/2 h were applied to dry the honey thin film for comparison. Test results show that both devices demonstrated bipolar resistive switching and neural facilitation behaviors, while the memristor with the honey film dried by 90 °C/8 h demonstrated a larger on/off ratio and read memory window, lower current at high-resistant state, and larger facilitation index. The index is also larger than our previously reported honey-memristor with same drying conditions but Ag top electrode, and memristors based on other natural organic materials such as chicken albumen and lignin. The index decayed following two exponential phases as a function of the interval time of the two stimulation voltage pulses, which is similar to biological synapses. Besides shorter pulse interval time, the response of facilitation also enhanced by larger magnitude and width of the stimulation voltage pulses. • Synaptic neural facilitation of honey-based memristor was investigated. • Largest facilitation gain in natural organic memristors was achieved. • The gains decay with pulse interval time, similar to biological synapses. • Larger pulse magnitude and pulse width, short interval of stimuli enhance the gain.

Ultrasensitive memristor-based gas sensor (gasistor) with gas-triggered switch and memory function for dilute NH3 detection

Accurately recording the time of toxic gas leakage is beneficial to find out the cause of the accident and evaluate the safety of the equipment. However, conventional gas sensors do not have the memory function without external storage devices. To develop gas sensors with both sensing and memory functions, memristor-based gas sensors have been proposed. The memristor-based gas sensors could be used as gas-triggered switch and gas sensors with a built-in memory, which was named gasistor. In this study, a TiO2-based gasistor was proposed for dilute NH3 detection at room temperature (RT). The gasistor displayed bipolar resistive switching behavior, excellent repeatability and stability. Gas-sensing measurements showed that TiO2-based gasistor could be used for ultrasensitive detection of NH3. The response to 1 ppm NH3 in the high resistance state (HRS) was as high as 164.2, and the response/recovery time was < 1 s, respectively. Especially, as the NH3 concentration decreased, the gasistor switched from the HRS to the low resistance state (LRS) and the NH3 leakage time was recorded. Based on the experimental results, we propose a more realistic gas-triggered switch mechanism model, which can be used to provide a reference for the prediction of gas-triggered voltage and compliance voltage.

Anodic Sb2S3 electrodeposition from a single source precursor for resistive random-access memory devices

In this paper we report the use of Na3[SbS4].9H2O as a single source precursor for the electrodeposition of Sb2S3 from aqueous electrolyte at pH 9.1. We present the electrochemistry of the [SbS4]3− anion and the redox processes observed for the deposited Sb2S3 film. We show that an amorphous Sb2S3 film can be deposited by anodic electrodeposition onto glassy carbon and that the by-product that accompanies this deposition can be avoided by using a suitable pulse plating approach. Raman spectroscopy and grazing incidence X-ray diffraction were used to characterise the deposits and to show that good quality crystalline films of Sb2S3 are produced on annealing.The crystalline Sb2S3 films were screened for application in Resistive Random-Access Memory, and it was demonstrated that crystalline Sb2S3 films display typical bipolar resistive switching behaviour, and that the resistance ratio between the high resistance state and the low resistance state is approximately one order of magnitude at 1.5 V, which is sufficient for memory applications. A mechanism for the resistive switching is also proposed.

Electrical studies of thermally annealed reduced graphene oxide-polymer nanocomposites

Resistive memory devices based on organic materials embedded with polymers have attracted growing attention in modern electronic and optoelectronic devices. Herein, a simple and cost effective methods are employed for the successful synthesis of graphene oxide (GO) and reduced graphene oxide (rGO) and exploited for non-volatile resistive memory application. Resistive switching characteristics of rGO-PVDF polymer nanocomposites (PNCs) sandwiched between top electrode copper (Cu) and bottom electrode (ITO/PET), is investigated here and the fabricated device Cu/rGO-PVDF/ITO shows excellent bipolar resistive switching behavior. The device shows VSET ∼ -5.61 V and VRESET ∼ 5.99 V, with ION/IOFF ∼ 102. Different optical, structural, and morphological investigations are also reported here to analyze the material behaviour.

Milk-Ta2O5 Hybrid Memristors with Crossbar Array Structure for Bio-Organic Neuromorphic Chip Applications.

In this study, a high-performance bio-organic memristor with a crossbar array structure using milk as a resistive switching layer (RSL) is proposed. To ensure compatibility with the complementary metal oxide semiconductor process of milk RSL, a high-k Ta2O5 layer was deposited as a capping layer; this layer enables high-density, integration-capable, photolithography processes. The fabricated crossbar array memristors contain milk–Ta2O5 hybrid membranes, and they exhibit bipolar resistance switching behavior and uniform resistance distribution across hundreds of repeated test cycles. In terms of the artificial synaptic behavior and synaptic weight changes, milk–Ta2O5 hybrid crossbar array memristors have a stable analog RESET process, and the memristors are highly responsive to presynaptic stimulation via paired-pulse facilitation excitatory post-synaptic current. Moreover, spike-timing-dependent plasticity and potentiation and depression behaviors, which closely emulate long-term plasticity and modulate synaptic weights, were evaluated. Finally, an artificial neural network was designed and trained to recognize the pattern of the Modified National Institute of Standards and Technology (MNIST) digits to evaluate the capability of the neuromorphic computing system. Consequently, a high recognition rate of over 88% was achieved. Thus, the milk–Ta2O5 hybrid crossbar array memristor is a promising electronic platform for in-memory computing systems.

Bipolar resistive switching behavior in Pt/Zn1−xMgxO/pyrographite/Pt structure for memory application

Bipolar resistive switching behavior in Pt/Zn1−xMgxO/pyrographite/Pt structure for memory application

Resistive switching in 2D bismuth oxyhalide nanosheets for nonvolatile memory and emulation of leaky integrate-and-fire functions

The resistive switching (RS) behaviors have been widely studied in a large number of two-dimensional (2D) materials. Bismuth oxyhalides have emerged as a typical ternary 2D layered material recently. However, the studies focusing on the RS behaviors in 2D bismuth oxyhalides are still limited. Herein, the RS behaviors in 2D BiOX (X = Cl, Br and Cl + Br) nanosheets have been systematically studied. 2D BiOX nanosheets are exfoliated from their bulk materials which are synthesized by a hydrothermal method. Vertical memristors with Pt/BiOX/Pt sandwiched structures have been fabricated for RS measurements. Among them, 2D BiOCl nanosheet has no RS behaviors. BiOBr nanosheet demonstrates non-volatile bipolar RS behaviors with a large ON/OFF ratio (∼105), long time retention (104 s) and good endurance (280 cycles) as well as good environmental stability, suggesting potential applications in non-volatile memory. Furthermore, BiOBr0.7Cl0.3 nanosheet shows volatile threshold switching (TS) behaviors with the ON/OFF ratio up to 105. The device with TS behaviors can be utilized to emulate the leaky integrate-and-fire (LIF) functions in biological synapses. This work demonstrates a new material with non-volatile or volatile RS behaviors, providing a new TS device for emulation of LIF activity.

Influence of non-inert electrode thickness on the performance of complementary resistive switching in AlOxNy-based RRAM

This Letter investigates the effect of non-inert electrode thickness on the performance of complementary resistive switching (CRS). Five devices with different Ta electrode thicknesses (0, 2, 5, 10, and 20-nm) are fabricated. For devices with 2, 5, and 10-nm electrode thicknesses, CRS behavior can be obtained through an evolution process, while devices with 0 and 20-nm Ta electrode thicknesses always maintain stable bipolar resistive switching behavior. By analyzing the evolution process and current conduction mechanisms, the influence of non-inert electrode thickness on the performance of CRS is studied, and different oxidation degrees of a non-inert electrode are used to explain the different resistive switching performance in these devices. Aside from that, the model is verified by applying an asymmetric voltage sweeping method. This paper further clarifies the physical mechanism of CRS behavior in non-inert electrode resistive random access memory and provides a way to optimize the performance of CRS behavior.

Enhancement of resistive switching behavior of organic resistive random access memory devices through UV-Ozone treatment

We fabricated organic resistive random-access memory (RRAM) devices using a low-cost solution-process method. All the processes were performed at temperatures below 135 °C under ambient atmospheric conditions. The RRAM resistive switching layer was formed from a polymer-fullerene bulk heterojunction using poly(3-hexylthiophene-2,5-diyl) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM). The fabricated organic RRAM device exhibited typical nonvolatile bipolar resistive switching behavior with an ON/OFF ratio of ∼40, but it provided a low endurance of 27 cycles. Therefore, for enhanced stability, simple UV–Ozone (UVO) treatment was applied to the P3HT:PCBM organic bulk heterojunction layer. The organic RRAM device with UVO treatment exhibited an enhanced performance with an ON/OFF ratio of ∼400 and an endurance of 47 cycles. In addition, complementary resistive switching behavior was observed. The conduction mechanisms of the organic RRAM device were investigated by fitting the measured I–V data to numerical equations, and Schottky emission and Ohmic conduction were the main conduction mechanisms for the high-resistance and low-resistance states for the RRAM device with or without UVO treatment.

Nonvolatile resistive memory and synaptic learning using hybrid flexible memristor based on combustion synthesized Mn-ZnO

Memristors have been seen as promising candidates for next-generation nonvolatile memory and neuromorphic computing. Solution-processed memristors can offer many advantages, such as low-cost fabrication, large-area uniformity, and high versatility. However, the high annealing temperature of the solution process and unsatisfactory performance are impeding the advancement of flexible memristors. In this work, the combustion method was proposed to fabricate the Mn-ZnO-based memristor without a high-temperature process on the flexible substrate. The device demonstrates stable bipolar resistive switching behavior with ultralow switching voltage (−0.6 V/0.71 V), high on/off ratio (˃ 2 × 103), multilevel storage capability, and uniform resistance distribution (σ/µ = 18%/16%). The flexible device with a bend radius of 10 mm shows no obvious performance degeneration compared with the device in the flat state. Furthermore, tunable repetitively synaptic weight was achieved by the memristor. Synaptic plasticity functions, such as excitatory postsynaptic current, paired-pulse facilitation, and learning/forgetting behaviors, have been emulated. This work provides a simple and feasible strategy for fabricating the flexible high-performance memristor, with the expectation to facilitate the development of flexible electronics.

Multifunctionality in ferromagnetic shape memory alloy-based resistive switching memory for flexible ReRAM application

Multifunctional flexible electronics is the ongoing demand for fabricating wearable data storage and communication devices. The magnetoelectric (ME) heterostructure consisting of piezoelectric (AlN) and ferromagnetic magnetic shape memory alloy [FSMA (Ni–Mn–In)] was fabricated over stainless steel (SS) substrate for resistive random access memory application. The Cu/AlN/FSMA/SS metal–insulator–metal based memory cell displays bipolar resistive switching (RS) behavior. The formation of Cu metallic filament at a particular SET voltage leads the memory cell in a low resistance state (LRS) from its pristine high resistance state (HRS). The LRS and HRS are explained well by Ohmic and space charge limited conduction mechanisms, respectively. The fabricated memory cell displays excellent endurance and data retention capability with a high OFF/ON ratio of ∼1.2 × 103. Furthermore, the multifunctionality of the ME heterostructure-based RAM was investigated by tuning the SET voltage with ambiance temperature and external magnetic field remotely. A significant change in the SET voltage could be ascribed to the temperature and magnetic field-induced strain transferred to the AlN piezoelectric layer from the magnetostrictive FSMA (Ni–Mn–In) bottom electrode. The residual Lorentz force explains the remotely tuned LRS and HRS in the transverse magnetic field for multi-bit data storage applications. Moreover, the RS characteristics remain stable even after 800 bending cycles as well as with bending angle (0°–180°). Hence, the present ME heterostructure integrated with flexible SS substrate can be a better choice for highly flexible, low-cost, and multifunctional futuristic RAM applications.

Tuning oxygen vacancies and resistive switching behaviors in amorphous Y2O3 film-based memories

Yttrium oxide (Y2O3) has attracted attentions as the new and promising functional material in resistive switching (RS) memories. However, the oxygen vacancies tuning by various electrodes is lack of understanding for Y2O3-based memories, which plays a crucial role for RS behaviors. Here, non-crystalline Y2O3 films prepared through magnetron sputtering deposition are used to construct RS memory devices with different structure. All the devices exhibit nonvolatile bipolar RS behaviors and the switching phenomena are depended on the formation/rupture of conductive filaments (CFs), which are composed of oxygen vacancies. In special, the Y2O3-based memories with Pt/Y2O3/Pt structure demonstrate competitive switching properties, including the ultra-lower set/reset voltages and high retention characteristic. Furthermore, the influence of different electrodes on oxygen vacancies, as well as morphologies of CFs, are discussed in detail. Besides that, physical models are proposed to further clarify carrier transport mechanisms and switching behaviors for memories with different structure. This study provides an in-depth understanding of the structural design and oxygen vacancies tunning by selecting electrodes in amorphous Y2O3 film-based RS memories.

Resistive switching properties of amorphous Sm2Ti2O7 thin film prepared by RF sputtering for RRAM applications

The resistive switching (RS) characteristics of amorphous Sm2Ti2O7 thin films prepared by using RF sputtering were investigated and the effect of post-metallization annealing (PMA) on the RS properties were analysed. Comparison of as-deposited Sm2Ti2O7 thin film device and the device after PMA treatment, the latter exhibits better RS properties, including more uniform set voltages, switching cycle times and higher Ron/Roff ratio. The prepared samples all revealed bipolar resistive switching (BRS) behaviour. The results indicated that the conductive mechanism in terms of the concentration of oxygen vacancies can be controlled by different deposition atmosphere (Ar/O2) ratio and film thickness. Additionally, the resistive switching properties can be enhanced by PMA treatment due to the formation of AlOx interface layer, which prevents the oxygen ions from out-diffusion through the boundaries. At the PMA temperature of 350 °C, the two resistance states can be distinguished in a range of> 10 over 8099 switching cycles along with a retention of 104 s at room temperature and 85ºC, showing promise for non-volatile memory applications.

A facile fabrication of lead-free Cs2NaBiI6 double perovskite films for memory device application

The environment-friendly Cs 2 NaBiI 6 double perovskite films have been fabricated using a one-step solution spin coating method in air. The X-ray diffraction analyzer, Ultraviolet-visible spectroscopy, scanning electron microscope, and X-ray photoelectron spectroscopy were carried out to characterize the films. The films were used to prepare the memory devices with the structure of Al/Cs 2 NaBiI 6 /ITO. The current−voltage characteristics of the devices clearly showed a bipolar resistive switching behavior. The estimated activation energy (~0.11 eV) proves that the conduction mechanism is mainly derived from the migration of iodine vacancies. Moreover, the devices showed the memory performances with an endurance up to 200 cycles, a higher ON/OFF ratio of over 10 2 , a long retention time ~10 4 s, and outstanding reproducibility. Especially, the devices still keep excellent memory behaviors with the increase of measurement temperatures up to 403 K or after 90 days exposure in the air. The results indicate that the present double perovskite memory devices with a remarkable stability offer a great potential for future applications. • Lead-free Cs 2 NaBiI 6 double perovskite films were fabricated by a one-step solution spin coating method. • The memory devices show large ON/OFF ratios, good endurance and long retention time. • The devices maintain excellent memory behaviors after 90 days exposure in the air.

Unipolar resistive switching behavior in MoS2–polyvinyl alcohol-based memory device

MoS2–polymer-based memory devices have attracted significant interest owing to their mechanical flexibility, convenient solution processability, and affordability. These devices exhibit bipolar resistive switching behavior, and their switching relies on the polarity of the applied bias. This paper presents a memory device in which a MoS2–polyvinyl alcohol (PVA) hybrid film is sandwiched between Ag and Pt electrodes. The developed Ag/MoS2–PVA/Pt device manifests typical unipolar resistive switching (URS) behavior and nonvolatile rewritable memory performance with a low operating voltage, large ON/OFF ratio (105), and multilevel cell storage ability. Notably, 1T-phase MoS2 is crucial for the URS behavior, and this switching behavior can be ascribed to the charge trapping as well as the Joule-heating-induced de-trapping of the S vacancies associated with 1T MoS2. These findings can facilitate the development of new designs for high-performance, high-density data storage.

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.