Bipolar Resistive Switching Behavior Research Articles

Multilevel resistive switching in hydrothermally synthesized FeWO4 thin film-based memristive device for non-volatile memory application

The memristors offer significant advantages as a key element in non-volatile and brain-inspired neuromorphic systems because of their salient features such as remarkable endurance, ability to store multiple bits, fast operation speed, and extremely low energy usage. This work reports the resistive switching (RS) characteristics of the hydrothermally synthesized iron tungstate (FeWO4) based thin film memristive device. The detailed physicochemical analysis was investigated using Rietveld’s refinement, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) techniques. The fabricated Ag/FWO/FTO memristive device exhibits bipolar resistive switching (BRS) behavior. In addition, the devices exhibit negative differential resistance (NDR) at both positive and negative bias. The charge-flux relation portrayed the non-ideal or memristive nature of the devices. The reliability in the RS process was analyzed in detail using Weibull distribution and time series analysis techniques. The device exhibits stable and multilevel endurance and retention characteristics which demonstrates the suitability of the device for the high-density non-volatile memory application. The current conduction of the device was dominated by Ohmic and trap controlled-space charge limited current (TC-SCLC) mechanisms and filamentary RS process responsible for the BRS in the device. In a nutshell, the present investigations reveal the potential use of the iron tungstate for the fabrication of memristive devices for the non-volatile memory application.

A bioinspired MXene-based flexible sensory neuron for tactile near-sensor computing

Multifunctional near-sensor computing sensory neurons based on the integration of flexible sensors and memristors hold promise to achieve unprecedented development in large-scale neuromorphic perception circuits and human-machine interaction systems. However, the traditional sensory-memory integrated systems are based on the integration of different device modules, which are subjected to redundant analog-to-digital conversion circuits and poor flexibility. Here, an all MXene-based flexible sensory neuron fabricated by a room temperature energy-efficient, and controllable oxidation preparation technique is reported. The near-sensor computing system is seamlessly integrated a MXene-based pressure sensor array for acquisition of tactile signals with a flexible MXene-based memristor array for simulating the implementation of perceived behavior. The tactile sensor array shows a wide range (0.1–100 kPa), high linear sensitivity (23.9 kPa−1), and the memristor array exhibits repeatable and stable bipolar resistive switching behavior (retention >100 cycles, endurance >103 s) and excellent flexibility (R=1.0 mm). As a conceptual demonstration, our devices realize high-precision recognition of handwritten digit recognition (93.21%) and human motion (97.96%), which demonstrate the feasibility for real-time health monitoring based on signals collected by sensors and artificial neural networks constructed by the memristors. The MXene-based sensor-memristor system offers a prominent contribution towards advanced application of intelligence in electronic skin and wearable electronic equipment.

Nymphaea Alba for Resistive Switching Devices: Exploring the Non‐Volatile Memory and Neuromorphic Computing Applications of the Plant Leaves

AbstractBiomaterial‐based resistive switching memory is one promising technology that could significantly impact the current direction of non‐volatile memory and neuromorphic computing. Given this, we report the fabrication of a resistive switching (RS) device based on Nymphaea Alba as an active switching layer and investigate its RS properties for memory and neuromorphic computing applications. The Nymphaea Alba switching layer was deposited by the conventional doctor blade method. Further, this is characterized by various analytical techniques. The fabricated device showed bipolar RS behavior and demonstrated good non‐volatile memory properties. Additionally, the device mimics various synaptic properties of the human brain, such as potentiation‐depression, Excitatory post‐synaptic current (EPSC), and Paired‐pulse facilitation (PPF). The charge‐flux relation reveals the non‐ideal memristor‐type behavior of the device. The Ohmic and Child's square law dominates the conduction of the device and the filamentary process responsible for the RS process of the device. These results show that the Nymphaea Alba is a promising biomaterial for non‐volatile memory applications.

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.

Light-Mediated Multilevel Flexible High-Efficiency Perovskite Resistive Switching Memory Based on Mn:CsPbCl3 Nanocrystals.

Herein, the electrical characteristics, photoelectric properties, resistive switching (RS) mechanism, and flexible storage application of Ag/PMMA&Mn:CsPbCl3/ITO (PMMA = poly(methyl methacrylate)) devices are studied by using the photoelectric material Mn:CsPbCl3 nanocrystals (NCs) embedded in PMMA as the RS layer. The devices exhibit bipolar RS behavior with low operating voltage, excellent cycling endurance (>1000 times), long retention time (≥104 s), high ON/OFF ratio (≈104), and good environmental stability. The flexible memory devices have demonstrated reliable mechanical stability of consecutive 1000 bending cycles. In addition, multilevel data storage is realized by introducing the UV light, and the adjustive resistive switching characteristics is achieved through photoelectric synergistic work. The resistive switching mechanism under the excitation of light has been studied comprehensively. This work may pave a new way for developing the next generation of high-density data storage and photoelectric memristor.

Low-Temperature Solution-Based Molybdenum Oxide Memristors.

Solution-based memristors have gained significant attention in recent years due to their potential for the low-cost, scalable, and environmentally friendly fabrication of resistive switching devices. This study is focused on the fabrication and characterization of solution-based molybdenum trioxide (MoO3) memristors under different annealing temperatures (200 to 400 °C). A MoO3 ink recipe is developed using water as the main solvent, enabling a simplified and cost-effective fabrication process. Material analysis reveals the presence of a Mo6+ oxidation state and an amorphous structure in the films annealed up to 250 °C. Electrical tests confirm a bipolar resistive switching behavior in the memristors according to the valence change mechanism (VCM). Endurance tests demonstrate stable memristors, indicating their robust nature after multiple cycles. Memristors annealed at 250 °C exhibit a nonvolatile behavior with a retention time up to 105 s under ambient air conditions. The high reproducibility observed in these memristors highlights their potential for practical applications and scalability.

Transmission Mechanism and Logical Operation of Graphene-Doped Poly(vinyl alcohol) Composite-Based Memristor.

Memristors are considered the best candidates for nonvolatile memory and advanced computing technologies, and polymer and two-dimensional (2D) materials have been developed as functional layer materials in memristors with high-performance resistive switching characteristics. In this work, a polymer memristor with a graphene (Gr)-doped poly(vinyl alcohol) (PVA) composite acting as the functional layer was prepared. The memristor device exhibited superior performance with good retention and a comparatively large ON/OFF ratio at room temperature. Additionally, excellent logic operations were achieved. These satisfactory properties can be attributed to trap-induced carrier trapping and detrapping. In addition, the device exhibited stable bipolar resistive switching behavior over a moderate temperature range. This work provides insight into the transmission mechanism of polymer-based memristors and the reasons why they become unstable at high temperatures, demonstrating the potential applications of PVA-Gr-based polymer memristors as logic circuit units in integrated chips and artificial intelligence.

Study of resistive switching behavior in HfO2 nanocrystals synthesized via a low temperature hydrothermal method

The resistive switching property in HfO2 have attracted increasing interest in recent years. In this work, amorphous HfO2 nanocrystals are synthesized by a facile hydrothermal method. Then, the as-synthesized nanocrystals are rapid thermal annealed in different atmospheres for improving the crystal quality, and monoclinic phase is determined as the main crystal structure of the annealed HfO2. Subsequently, metal–insulator–metal structure devices based on HfO2 samples are fabricated. Electrical measurement indicates that 700 °C annealing processes in Air and Ar environments can slightly improve the bipolar resistive switching and retention behaviors. Higher annealed temperature (900 °C) will further improve the crystal quality of HfO2, while the resistive switching and retention behaviors of the devices continuously attenuate, which can be ascribed to the reduction of the conductive filaments induced by defects.

Exploring non-stoichiometric SiOx thin film for non-volatile memory application

This article explores the electrical performance of capacitive memory and resistive switching (RS) devices based on thin films of a single active layer of Silicon oxide (SiOx). The fabricated device Au/SiOx/p-Si displayed frequency-dependent characteristics ranging from 200 kHz to 1 MHz w.r.t capacitance. The charge trapping nature was also investigated, which revealed a charge storage density (N) of order 1010 cm−2 and a low trapping density of interface (Dit) ∼2.65 × 1011 eV−1 cm−2. Furthermore, the device exhibits bipolar RS behavior while maintaining a stable endurance for 1000 DC sweeping cycles and a good retention period of > 103 s. The major pathway of the conduction mechanism in these devices is attributed to the accumulation of oxygen vacancies near the Au/SiOx interface. The conduction in this device is predominantly governed by trap-mediated space-charge-limited current (SCLC) and ohmic conductions.

Cobalt sulfide films by sulfurizing cobalt for resistive switching memory

A cobalt sulfide (CoS x ) film compromising CoS2 and Co9S8 nanograins was formed by sulfurizing the surface of a Co film to use for resistive switching (RS) memory. The work function and band gap of the CoS x film were measured to be 4.78 eV and 2.18 eV, respectively. The CoS x film was used as a resistive layer together with the Co film underneath as a bottom electrode, and a Ag or Cu film as the top electrode. Both Ag/CoS x /Co and Cu/CoS x /Co devices exhibited bipolar RS behavior with the capability of multi-level memory storage. The conduction of both devices in low resistive states was correlated with metallic filamentary paths following ohmic conduction, whereas Schottky emission originated at the Ag/CoS x and Cu/CoS x interfaces dominated in the high resistance state. The performance of Ag/CoS x /Co and Cu/CoS x /Co devices were compared and correlated with the properties of Ag and Cu electrodes.

Multi-factors-regulated multi-level down-scalable and robust memristors

The memristor based on resistive switching (RS) behavior has attracted extensive attention due to its wide application prospects in artificial intelligence (AI) and information memory. In this work, a multi-factor responsive memristor based on Ag/MnO2/F-doped tin oxide (FTO) sandwich structure was fabricated by magnetic sputtering method. It was found that the RS behavior of the device was significantly improved when the diameter of the top electrode decreased from 2.0 mm to 0.5 mm, indicating that the device with Ag/MnO2/FTO structure has the down-scalable potential. Through comprehensive research, it can be concluded that the bipolar RS behavior of the memristor can be adjusted by multi-factors such as active layer thickness, top electrode size, voltage scanning rate, bias voltage amplitude and temperature. Specifically, the resistance-temperature dependence and temperature coefficient of the device in the low resistance state (LRS) indicate that the formation and disconnection of metallic Ag conductive filaments (CFs) play an important role in the RS behavior of the memristive device. Therefore, this work will lay an experimental and theoretical foundation for comprehensively understanding the mechanism of RS behavior and developing high-performance memristor with multi-level memory capacity.

Rapid Semiconducting Supramolecular Mg(II)-Metallohydrogel: Exploring Its Potential in Nonvolatile Resistive Switching Applications and Antiseptic Wound Healing Properties.

An effective strategy was employed for the rapid development of a supramolecular metallohydrogel of Mg(II) ion (i.e., Mg@PEHA) using pentaethylenehexamine (PEHA) as a low-molecular-weight gelator in aqueous medium under ambient conditions. The mechanical stability of the synthesized Mg@PEHA metallohydrogel was characterized by using rheological analysis, which showed its robustness across different angular frequencies and oscillator stress levels. The metallohydrogel exhibited excellent thixotropic behavior, which signifies that Mg@PEHA has a self-healing nature. Field emission scanning electron microscopy and transmission electron microscopy images were utilized to explore the rectangular pebble-like hierarchical network of the Mg@PEHA metallohydrogel. Elemental mapping through energy-dispersive X-ray spectroscopy analysis confirmed the presence of primary chemical constituents in the metallohydrogel. Fourier transform infrared spectroscopy spectroscopy provided insights into the possible formation strategy of the metallohydrogel. In this work, Schottky diode structures in a metal-semiconductor-metal geometry based on a magnesium(II) metallohydrogel (Mg@PEHA) were constructed, and the charge transport behavior was observed. Additionally, a resistive random access memory (RRAM) device was developed using Mg@PEHA, which displayed bipolar resistive switching behavior at room temperature. The researchers investigated the switching mechanism, which involved the formation or rupture of conduction filaments, to gain insights into the resistive switching process. The RRAM device demonstrated excellent performance with a high ON/OFF ratio of approximately 100 and remarkable endurance of over 5000 switching cycles. RRAM devices exhibit good endurance, meaning they can endure a large number of read and write cycles without significant degradation in performance. RRAM devices have shown promising reliability in terms of long-term performance and stability, making them suitable for critical applications that require reliable memory solutions. Significant inhibitory activity against the drug-resistant Klebsiella pneumonia strain and its biofilm formation ability was demonstrated by Mg@PEHA. The minimum inhibitory concentration value of the metallohydrogel was determined to be 3 mg/mL when it was dissolved in 1% DMSO. To study the antibiofilm activity, an MTT assay was performed, revealing that biofilm inhibition (60%) commenced at 1 mg/mL of Mg@PEHA when dissolved in 1% DMSO. Moreover, in the mouse excisional wound model, Mg@PEHA played a crucial role in preventing postoperative wound infections and promoting wound healing.

Exploration of a wide bandgap semiconducting supramolecular Mg(II)-metallohydrogel derived from an aliphatic amine: a robust resistive switching framework for brain-inspired computing

A rapid metallohydrogelation strategy has been developed of magnesium(II)-ion using trimethylamine as a low molecular weight gelator in water medium at room temperature. The mechanical property of the synthesized metallohydrogel material is established through the rheological analysis. The nano-rose like morphological patterns of Mg(II)-metallohydrogel are characterized through field emission scanning electron microscopic study. The energy dispersive X-ray elemental mapping analysis confirms the primary gel forming elements of Mg(II)-metallohydrogel. The possible metallohydrogel formation strategy has been analyzed through FT-IR spectroscopic study. In this work, magnesium(II) metallohydrogel (Mg@TMA) based metal–semiconductor-metal structures have been developed and charge transport behaviour is studied. Here, it is confirmed that the magnesium(II) metallohydrogel (Mg@TMA) based resistive random access memory (RRAM) device is showing bipolar resistive switching behaviour at room temperature. We have also explored the mechanism of resistive switching behaviour using the formation (rupture) of conductive filaments between the metal electrodes. This RRAM devices exhibit excellent switching endurance over 10,000 switching cycles with a large ON/OFF ratio (~ 100). The easy fabrication techniques, robust resistive switching behaviour and stability of the present system makes these structures preferred candidate for applications in non-volatile memory design, neuromorphic computing, flexible electronics and optoelectronics etc.

Analog resistive switching behavior in BiCoO3 thin film

In this work, resistive switching behaviour of BiCoO3 (BCO) thin film has been reported. The BCO thin film was grown on ITO coated corning glass substrate using pulsed laser deposition (PLD) technique at a substrate temperature of 550 ˚C in the presence of oxygen ambient pressure of 200 mT. The Al/BCO/ITO device was found to exhibit analog bipolar resistive switching behaviour, as no electroforming was needed in this study. The device was found to be compliance free. The current voltage characteristics was studied and found it follows Ohmic and SCLC conduction mechanism in LRS mode and Ohmic, SCLC and Schottky emission conductions in HRS mode for both positive and negative cycles respectively. The endurance test of the Al/BCO/ITO device was performed to study the switching capability of the fabricated device upto 103 cycles and found stable. Retention characteristics were also studied and found stable over a period of time > 103 s. The device active area dependent studies was included and found that the device shows interface type RS for both LRS and HRS mode at 0.5 V and −0.5 V the resistance was found to be decreasing on increasing device active area. A conduction model was included to justify the interfacial conduction in the present device. Thus, non-volatile nature and stablility of the present Al/BCO/ITO RRAM device makes it a potential candidate to future analog RRAM devices.

Magnetic, Antiferroelectric-like Behavior and Resistance Switching Properties in BiFeO3-CaMnO3 Polycrystalline Thin Films

The effect of ferromagnetic CaMnO3 (CMO) addition to structural, magnetic, dielectric, and ferroelectric properties of BiFeO3 is presented. X-ray diffraction and Raman investigation allowed the identification of a single pseudocubic perovskite structure. The magnetic measurement showed that the prepared films exhibit a ferromagnetic behavior at a low temperature with both coercive field and remnant magnetization increased with increasing CMO content. However, a deterioration of magnetization was observed at room temperature. Ferroelectric study revealed an antiferroelectric-like behavior with a pinched P–E hysteresis loop for 5% CMO doping BFO, resulting in low remnant polarization and double hysteresis loops. Whereas, high remnant polarization and coercive field with a likely square hysteresis loop are obtained for 10% CMO addition. Furthermore, a bipolar resistive switching behavior with a threshold voltage of about 1.8 V is observed for high doped film that can be linked to the ferroelectric polarization switching.

Synaptic memristors based on flexible organic pentacene thin films by the thermal evaporation method for neuromorphic computing

As the development of neuromorphic computing, it is meaningful to explore the synaptic memristors based on organic materials owing to their advantages in low cost, good mechanical flexibility and strong biocompatibility. In this work, organic pentacene thin films have been deposited on different substrates by the thermal evaporation method. The prepared thin films on SiO2/Si substrates demonstrate the co-existence of digital and analog resistive switching (RS) behaviors as well as a series of synaptic plasticity. To characterize the flexibility of the organic thin films, lateral memristors have been fabricated on polyethylene terephthalate (PET) substrates and demonstrate comparable RS behaviors when the bending radius is decreased to 1.26 cm or after 1000 bending. Furthermore, vertical memristors with Pt/pentacene/indium tin oxide (ITO) structure have been constructed when the organic thin films are deposited on ITO/PET substrates, exhibiting bipolar RS behaviors with low SET voltage of 0.65 V. The vertical synaptic memristors can be used to simulate the “learning-forgetting” experience of human brain. More importantly, an artificial neural network (ANN) can be simulated based on the vertical synaptic memristors, demonstrating 93.8 % recognition accuracy for hand-written digit image. This study suggests potential applications of the organic pentacene thin films for neuromorphic computing.

Occurrence of robust memristive behavior for low-power transient resistive switching and photo-responsive neuromorphic computing in low-dimensional perovskite

Recent progress on the memristive devices owing to the multi-functional approach have surged the exploration of new functional materials. Here, we have incorporated two-dimensional (2D) halide perovskite in memristive device. The Pb-free Cs3Bi2I9 perovskite active layer was fabricated to obtain the ITO/Cs3Bi2I9/Pt structure. The device shows typical bipolar resistance switching behavior with Off state resistance in TΩ scale. Due to the higher work function of the top Pt electrode, the barrier height at the Pt/Cs3Bi2I9 junction is higher and the observed device conductance is low in the Off state. Enhanced memory parameters such as endurance (>103 cycles) and retention (104 s) for multiple conductance states is observed. In the pulse modulated synaptic characterization, the device emulated essential post-synaptic plasticity, short-term and long-term potentiation with power consumption in femto Joule. The classical conditioning learning was mimicked by the device by electric and optical stimulation procuring basic associative training. The non-toxicity of the perovskite material has been successfully utilized for the transient memristor application. The robust in-memory photonic memristive property of the device along with water stimulated transient behavior demonstrates the significance of the proposed device in multi-dimensional field of electronic device.

Bipolar resistive switching behavior and endurance in RF-sputtered bilayer HfO2/ZrO2 resistive random access memory

Bipolar resistive switching behavior and endurance in RF-sputtered bilayer HfO2/ZrO2 resistive random access memory

Implementation of Stable Nonvolatile Resistive Switching Behaviors in TiO2 Nanoparticle‐Incorporated 2D Layered Halide Perovskite‐Based Devices

2D organic–inorganic layered halide perovskites have received tremendous interest as promising materials in electronics owing to their outstanding physical properties. However, the quantum confinement effect leads to the suppression of ion migration in the out‐of‐plane direction, restricting their applications in resistive switching (RS) memories with vertical structure. Herein, the 2D layered perovskite incorporated with TiO2 nanoparticles, denoted as TiO2–PEA2PbBr4, is employed, as the functional layers to construct RS memory devices with Al/TiO2–PEA2PbBr4/ITO structure. As compared to pure 2D layered perovskite counterparts without switching behaviors, the Al/TiO2–PEA2PbBr4/ITO memories demonstrate stable bipolar RS behaviors, along with striking characteristics, including the relatively centralized set/reset voltages, a large on/off ratio (≈102), and a long retention time (104 s). In addition, the devices also present the multilevel storage capability by controlling the compliance current. Moreover, the RS behaviors are attributable to the formation/rupture of synergy bromine and oxygen vacancy conductive filaments, owing to their migration/distribution of oxygen/bromine ions under electric fields. The oxide nanoparticles incorporation route provides an effective strategy for improving RS performance in 2D layered perovskite‐based RS memories.

Effects of rubidium substitution of Cs2−xRbxAgBiBr6 double halide perovskites on resistive switching characteristics for memory applications

Cation substitution technique in halide perovskites (HPs) is one of the famous schemes to enhance the characteristics of HPs-based electronic and optoelectronic devices. Here, we fabricated rubidium (Rb) substituted inorganic double halide perovskites (HPs) Cs2−xRbxAgBiBr6 (x = 0, 0.05, 0.1, 0.2, and 0.3) film-based resistive switching (RS) devices and investigated effects of Rb cation substitution on characteristics of RS devices. Grain sizes of the formed Cs2−xRbxAgBiBr6 films gradually increased as increase of Rb contents in the precursor. All of the fabricated RS devices demonstrated non-volatile bipolar RS behavior, device with the Rb content x = 0.1 showed a particularly high on/off ratio (9.29 × 102) of about 30 times greater than pristine Cs2AgBiBr6-based ones (3.09 × 10). In addition, it has been shown that an appropriate amount of Rb substitution at the level of x = 0.1 can effectively prevent the appearance of other crystalline phases at high humidity condition of > 80 %. Through various analytical techniques including SEM, XPS, and SCLC measurement, it was confirmed that an enlargement in grain size resulting in a decrease in defects such as Br vacancies in the fabricated film can lead to an increase in resistance at a high resistance state (HRS) and high on/off resistance ratio. This study provides a facile and feasible way to enhance performances of HPs-based RS devices for practical electronic memory applications.