Reversible Resistive Switching Behavior Research Articles

Investigation of Grain Boundary Effects in Sm0.2Ce0.8O2-x Thin Film Memristors.

Cerium-based materials (CeO2-x) are of significant interest in the development of vacancy-modulated resistive switching (RS) memory devices. However, the influence of grain boundaries on the performance of memristors is very limited. To fill this gap, this study explores the influence of grain boundaries in cerium-based thin film resistive random-access memory (RRAM) devices. Sm0.2Ce0.8O2-x (SDC20) thin films were deposited on (100)-oriented Nb-doped SrTiO3 (NSTO) and (110)-oriented NSTO substrates using pulsed laser deposition (PLD). Devices constructed with a Pt/SDC20/NSTO structure exhibited reversible and stable bipolar resistive switching (RS) behavior. The differences in conduction mechanisms between single-crystal and polycrystalline devices were confirmed, with single-crystal devices displaying a larger resistance window and higher stability. Combining the results of XPS and I-V curve fitting, it was confirmed that defects near the grain boundaries in the SDC-based memristors capture electrons, thereby affecting the overall performance of the RRAM devices.

Si/CuO Heterojunction-Based Photomemristor for Reconfigurable, Non-Volatile, and Self-Powered In-Sensor Computing.

In-sensor computing has attracted considerable interest as a solution for overcoming the energy efficiency and response time limitations of the traditional von Neumann architecture. Recently, emerging memristors based on transition-metal oxides (TMOs) have attracted attention as promising candidates for in-memory computing owing to their tunable conductance, high speed, and low operational energy. However, the poor photoresponse of TMOs presents challenges for integrating sensing and processing units into a single device. This integration is crucial for eliminating the need for a sensor/processor interface and achieving energy-efficient in-sensor computing systems. In this study, a Si/CuO heterojunction-based photomemristor is proposed that combines the reversible resistive switching behavior of CuO with the appropriate optical absorption bandgap of the Si substrate. The proposed photomemristor demonstrates a simultaneous reconfigurable, non-volatile, and self-powered photoresponse, producing a microampere-level photocurrent at zero bias. The controlled migration of oxygen vacancies in CuO result in distinct energy-band bending at the interface, enabling multiple levels of photoresponsivity. Additionally, the device exhibits high stability and ultrafast response speed to the built-in electric field. Furthermore, the prototype photomemristor can be trained to emulate the attention-driven nature of the human visual system, indicating the tremendous potential of TMO-based photomemristors as hardware foundations for in-sensor computing.

Multistate structures in a hydrogen-bonded polycatenation non-covalent organic framework with diverse resistive switching behaviors

The inherent structural flexibility and reversibility of non-covalent organic frameworks have enabled them to exhibit switchable multistate structures under external stimuli, providing great potential in the field of resistive switching (RS), but not well explored yet. Herein, we report the 0D+1D hydrogen-bonded polycatenation non-covalent organic framework (HOF-FJU-52), exhibiting diverse and reversible RS behaviors with the high performance. Triggered by the external stimulus of electrical field E at room temperature, HOF-FJU-52 has excellent resistive random-access memory (RRAM) behaviors, comparable to the state-of-the-art materials. When cooling down below 200 K, it was transferred to write-once-read-many-times memory (WORM) behaviors. The two memory behaviors exhibit reversibility on a single crystal device through the temperature changes. The RS mechanism of this non-covalent organic framework has been deciphered at the atomic level by the detailed single-crystal X-ray diffraction analyses, demonstrating that the structural dual-flexibility both in the asymmetric hydrogen bonded dimers within the 0D loops and in the infinite π–π stacking column between the loops and chains contribute to reversible structure transformations between multi-states and thus to its dual RS behaviors.

Optoelectronic Synaptic Memtransistor Based on 2D SnSe/MoS2 van der Waals Heterostructure under UV-Ozone Treatment.

Memristive switching devices with electrically and optically invoked synaptic behaviors show great promise in constructing an artificial biological visual system. Through rational design and integration, 2D materials and their van der Waals (vdW) heterostructures can be applied to realize multifunctional optoelectronic devices. Here, a multifunctional optoelectronic synaptic memtransistor based on a SnSe/MoS2 vdW p-n heterojunction to simulate the human biological visual system is reported. By employing simple mild UV-ozone treatment, the device exhibits reversible resistive switching (RS) behavior with switching ratio up to 103 . The retina-like selective response to different input light wavelengths is activated, as well as programmable multilevel resistance states and long-term synaptic plasticity. Moreover, memory and logic functions analogous to those found in the visual cortex of the brain are performed by controlling the optical and electrical input signals. This work proposes a feasible strategy to modulate RS in vdW heterostructures for memristive devices, which show significant potential for neuromorphic processing.

Tunable, reversible resistive switching behavior of PVA-zirconia nanocomposite films and validation of the trap-assisted switching mechanism by the selective application of external bias voltages.

Flexible, free-standing polyvinyl alcohol (PVA)-zirconia (mean particle size ∼24 nm) nanocomposite films have been synthesized and their performance as a potential next-generation resistive switching device material has been assessed in this report. The nanocomposite films switch from a high resistive state (HRS) to a low resistive state (LRS) at the SET potential and from LRS to HRS at the RESET potential within the voltage window of 5 V. The origination of trap-assisted SET/RESET potentials has been experimentally validated by analyzing the experimental data and invoking various theoretical models. The impregnation of zirconium dioxide (ZrO2) nanoparticles considerably enhances the interfacial charges facilitated by the formation of dangling bonds. The current (I)-voltage (V) characteristics elucidate how the alteration of free volumetric space in the nanocomposites can modify the SET-RESET potential. This leads to tunable SET/RESET potential, good resistance ratio (∼80), and extensive cycling ability of these PVA-ZrO2 organic flexible nanocomposite films. Herein, we have also investigated the effect of applying external bias voltage (equal to the RESET potential) for possible energy bandgap modification and polymer chain orientation. The impedance spectra differ considerably when the sample is subjected to SET, RESET, and zero voltage bias. The observations have been correlated with the UV-vis absorption spectra and electrical studies. The adopted analysis method and obtained results can open up new avenues for designing and analyzing resistive switching-based random-access memory devices.

Intelligent resistive-switching EWOD device based on the Fe doped ZnO memristor

Multi-functionalization and intellectualization are the main goal for the development of various excellent device. Resistive-switching memristor is an emerging artificial intelligence device. Combining resistive switching with electrowetting-on-dielectric (EWOD) is a pioneering idea to fulfill the multifunctional and intelligent resistive-switching EWOD device. In the paper, Fe doped ZnO memristors have been successfully prepared by a simple hydrothermal method, and exhibit reversible electronic resistive switching behavior, which is mainly attributed to the electron trapping and detrapping from the introduced oxygen vacancies by Fe doping. The surface structure of hierarchical dual-layer nanorod array endows the prepared ZnO memristors with reversible EWOD response of low energy consumption, which enables the device to satisfy the development of excellent EWOD device. Through the in-depth study, the stable high and low resistive states of prepared Fe doped ZnO memristors have distinct surface wetting properties, and the liquid droplet on the memristors can be intelligently controlled, and realize the resistive-switching EWOD intelligent device. The work gives a new way to the development of excellent artificial intelligence liquid switch and devices.

Electrically and Optically Controllable p-n Junction Memtransistor Based on an Al2 O3 Encapsulated 2D Te/ReS2 van der Waals Heterostructure.

The exploration of memtransistors as a combination of a memristor and a transistor has recently attracted intensive attention because it offers a promising candidate for next-generation multilevel nonvolatile memories and synaptic devices. However, the present state-of-the-art memtransistors, which are based on a single material, such as MoS2 or perovskite, exhibit a relatively low switching ratio, require extremely high electric fields to modulate bistable resistance states and do not perform multifunctional operations. Here, the realization of an electrically and optically controllable p-n junction memtransistor using an Al2 O3 encapsulated 2D Te/ReS2 van der Waals heterostructure is reported. The hybrid memtransistor shows a reversible bipolar resistance switching behavior between a low resistance state and a high resistance state with a high switching ratio up to 106 at a low operating voltage (<10V), high cycling endurance, and long retention time. Moreover, multiple resistance states are achieved by applying different bias voltages, gate voltages, or light powers. In addition, logical operations, including the inverter and AND/OR gates, and synaptic activities are performed by controlling the optical and electrical inputs. The work offers a novel strategy for the reliable fabrication of p-n junction memtransistors for multifunctional devices and neuromorphic applications.

Bipolar Resistive Switching in Magnetostrictive Ni/PZT/Pt Structure for Non-Volatile Memory Applications

Resistive switching (RS) has significant potential for the forthcoming generation in logical and non-volatile memory devices. Owing to their switchable spontaneous polarization ferroelectric materials can be utilized for non-volatile memory applications, e.g., FeRAM, but their destructive readout scheme limits applications. The spontaneous electrical polarization of ferroelectric materials enhances the tuning charge properties at the ferroelectric/metal interface making them appropriate for RS applications. Here, the resistive switching performance of ferroelectric Pb(Zr0.6Ti0.4)O3 (PZT) thin film grown on flexible Ni substrate using pulsed laser deposition were investigated. The PZT film showed both entrenched P-E ferroelectric hysteresis loop and reversible resistive switching behaviors with DC voltage sweep. Bipolar switching between a low resistance state to a high resistance state with a large ON/OFF ratio of 102 and resistance retention potential up to 1010 cycles was observed. The current conduction mechanism can be understood by dual logarithm I-V curve fitting. The obtained results encourage the utilization of prepared Ni/PZT/Pt widget for the non-volatile memory applications.

Optical and resistive switching properties of Chitosan-aluminum-doped zinc oxide composite thin films for transparent resistive random access memory application

The preparation of chitosan-aluminum-doped zinc oxide (AZO) composite thin films for transparent resistive random access memory applications is reported. The variation in optical transmission, refractive index and optical bandgap of the composite films as a function of concentration of Al in ZnO and AZO weight percent in chitosan is investigated. Independent of composition, optical transmission is of the order of 87–89% at 550 nm. The refractive index at this wavelength is in the range of 1.71–1.86. The composite films exhibit reversible resistive switching behavior which is dependent on the Al concentration in ZnO as well as the weight percent of AZO in chitosan. There is a threshold Al concentration in ZnO, below and above which resistive switching is not observed. At the threshold concentration, resistive switching behavior is stable over several cycles. The co-existence of unipolar and bipolar switching controlled by Al concentration in ZnO is also observed. The current study establishes the potential of chitosan-AZO composite thin films for transparent resistive random access memory application.

Organic spin valves with nonvolatile memory using molecular doping

Recently, several multifunctional organic spin valves (OSVs) integrating both magnetoresistance (MR) effect and nonvolatile memory effect were reported. In most cases, single unmodified organic layers were employed, and the underlying mechanism of the memory effect was not fully understood. Here, we present a simple and effective method to achieve nonvolatile memory in OSVs by doping the organic interlayer of the sandwich device, which will introduce traps in the organic interlayer and affect charge and spin transport. The doped OSVs exhibit a current-voltage hysteresis and reversible resistive switching behavior, indicating that the nonvolatile memory is achieved. The trap-controlled space-charge-limited current model can explain the memory effect of the doped OSVs, and combined with spin diffusion theory based on hyperfine interaction it can also explain the corresponding MR changes under different resistance states.

An electro-thermal computational study of conducting channels in dielectric thin films using self-consistent phase-field methodology: A view toward the physical origins of resistive switching

A large number of experimental studies suggest that two-terminal resistive switching devices made of a dielectric thin film sandwiched by a pair of electrodes exhibit reversible multi-state switching behaviors; however, coherent understanding of physical and chemical origins of their electrical properties needs to be further pursued to improve and customize the performance. In this paper, phase-field methodology is used to study the formation and annihilation of conductive channels, resulting in reversible resistive switching behaviors that can generally occur in any dielectric thin films. Our focus is on the dynamical evolution of domains made of electrical charges under the influence of a spatially varying electric field and a temperature, resulting in distinctive changes in electrical conductance.

A Flexible Transient Biomemristor Based on Hybrid Structure HfO2/BSA:Au Double Layers

AbstractBiomemristors have attracted increasing attention in neuromorphic computing as artificial biosynapses for wearable and implantable electronic systems. So far, biomemristors have achieved a series of neural outstanding functions, such as long‐term enhancement and long‐term inhibition, spiking‐time‐dependent plasticity, and paired impulse promotion, which has further developed memristors in the field of neurobionics. However, there is a problem in conventional memristors regarding the growth position and nucleation dynamics of the conductive filaments since they cause unstable switching parameters. In this study, a new hybrid structure with HfO2/BSA:Au (bovine serum doped with nanogold) is designed to improve biomemristor performance. The Ag/HfO2/BSA:Au/Pt stacked devices show a reversible and excellent bipolar resistive switching behavior. Moreover, the device can faithfully emulate the apoptotic process of biological synapses. Also, the same structure is constructed on a polydimethylsiloxane flexible substrate to examine the biosynapse's functional performance under bending conditions. Finally, the memristor cell can be completely dissolved in deionized water. The hybrid biomemristor can open up a new route to improve the reliability of the biomemristor based on the overall device performance of the BSA:Au, which could significantly accelerate hybrid biomemristor practical applications in wearable, degradable, or implantable electronic systems.

Effect of deposition temperature on ultra-low voltage resistive switching behavior of Fe-doped SrTiO3 films

The effect of deposition temperature on the microstructures and resistive switching properties of Fe-doped SrTiO3 (Fe-STO) films deposited via magnetron sputtering has been investigated. The as-deposited Fe-STO films change from amorphous to polycrystalline when the deposition temperature increases to 600 °C, but 800 °C-deposited Fe-STO films exhibit cracked surface morphologies with Sr-rich nanosheet segregation. Fe-STO films deposited at ≤600 °C exhibit reversible bipolar resistive switching behaviors with ultra-low switching voltages of &amp;lt;±0.6 V, while 450 °C-deposited Fe-STO films retain an ON/OFF resistance ratio of ∼105 after more than 2500 endurance cycles and 600 °C-deposited Fe-STO films exhibit three different resistive switching patterns in sequence. Fe-assisted oxygen-vacancy conductive filaments are responsible for the ultra-low voltage resistive switching behaviors of Fe-STO films.

The evolution of resistive switching behaviors dependent on interface transition layers in Cu/Al/FTO nanostructure

Here, the Cu/Al/FTO layered nanostructure was designed and manufactured for investigating the roles of the interface transition layers in its resistive switching (RS) behaviors. The presence of the interface transition layers was confirmed by X-ray photoelectron spectroscopy (XPS) depth profile scans, indeed there is a very thin Al2O3 interface transition layer (interface 1, denoted as I1) produced by the natural oxidation within the Cu/Al interfaces, and a thicker interface transition layer (interface 2, denoted as I2, consisting of Al, Al2O3, SnO and SnO2) generated by interdiffusion and redox reaction between the Al/FTO interfaces. The test results showed that the device, with actual structure of Cu/I1/Al/I2/FTO, could show the evolution of resistive switching behaviors: from irreversible write-once-read-many-times (WORM) characteristics to reversible bipolar resistive switching (BRS) behaviors with negative differential resistance (NDR) effect and subsequent disappearance and recovery of the BRS. Correlation analysis suggests the observed RS behaviors strongly depend on the permanent rupture of pre-existing Al conductive filaments (Al-CFs) in the transition layer I2, and their evolution. This work gives an insight into the role of interface transition layers in RS behaviors and provides a simple way to design and build new sandwiched nanostructure using for nonvolatile memory.

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

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

Resistive switching behaviors in the BaTiO3/La0.7Sr0.3MnO3 layered heterostructure driven by external electric field

By controlling the polarization direction of BaTiO3 (BTO) layer, the nonvolatile and reversible resistive switching behavior of the BaTiO3/La0.7Sr0.3MnO3 (BTO/LSMO) layered heterostructure have been observed. Pulsed laser deposition (PLD) technique was used to prepare it on the (0 0 1) oriented single-crystal SrTiO3 (STO) substrate, and its magnetic and electric properties were studied. Moreover, the change of the resistivity and metal–insulator transition temperature (TMI) for the LSMO layer were found to be induced by the switching of the electric field direction. The resistivity is decreased while the TMI is increased for the accumulation state of hole carriers when a negative electric field is applied to the BTO layer. By contrast, the resistivity is increased while the TMI is decreased for the depletion state of hole carriers when a positive electric field is applied to the BTO layer. This result indicates a nonvolatile and reversible resistive switching behavior in the multiferroic heterostructure control through the external electric field on ferroelectric layer, which provides a platform to develop unique electronic devices, such as nonvolatile random-access memories, sensors and memristive devices, etc.

Resistive Switching in Semimetallic SrIrO3 Thin Films

Local electrical properties, measured by conductive atomic force microscopy, of semimetallic SrIrO3 thin films are reported. The appearance of an Anderson-type metal–insulator transition (MIT) triggered by disorder and spatial localization due to film thickness reduction is analyzed as well as their influence on the resistive switching behavior. For thin enough films (below ∼3 nm) samples are insulating with hysteretic I–V curves indicative of reversible resistive switching behavior between two states of clearly different resistance at room temperature. A sharp transition into a low resistance state (LRS), i.e., an abrupt increase of the current intensity, is detected above a well-defined threshold voltage indicative of localization of charge carriers. On the other hand, thicker samples exhibit a semimetallic character, and I–V curves show progressive changes of the local resistance without a clearly defined threshold voltage, thus evidencing the absence of a MIT transition with a well-defined resistance jump between the different resistance states.

Resistive switching in Si2Te3 nanowires

As a silicon-based chalcogenide, semiconducting Si2Te3 has recently attracted attention as an emerging layered 2D material. Here, single-crystalline Si2Te3 nanowires (NWs) are synthesized by chemical vapor deposition (CVD). The Si2Te3 NWs grow along the [0001] direction, which is perpendicular to the 2D layers. The NWs exhibit a unique reversible resistance switching behavior driven by an applied electrical potential, which leads to switching of the NWs from a high-resistance state to a low-resistance state. This switched state is stable unless the opposite potential is applied to switch the resistance back. It is also noted that the polarity of the initially applied potential along the NWs defines the switch on and off directions, which become permanent once set. In combination with theoretical calculations, the resistance switching is explained by an internal structural change resulting from the applied potential. This novel resistance switching property for the silicon-based 2D materials is not only interesting for fundamental exploration but also holds promise for applications in memory devices.As a silicon-based chalcogenide, semiconducting Si2Te3 has recently attracted attention as an emerging layered 2D material. Here, single-crystalline Si2Te3 nanowires (NWs) are synthesized by chemical vapor deposition (CVD). The Si2Te3 NWs grow along the [0001] direction, which is perpendicular to the 2D layers. The NWs exhibit a unique reversible resistance switching behavior driven by an applied electrical potential, which leads to switching of the NWs from a high-resistance state to a low-resistance state. This switched state is stable unless the opposite potential is applied to switch the resistance back. It is also noted that the polarity of the initially applied potential along the NWs defines the switch on and off directions, which become permanent once set. In combination with theoretical calculations, the resistance switching is explained by an internal structural change resulting from the applied potential. This novel resistance switching property for the silicon-based 2D materials is not only in...

Significantly-enhanced Stabilities in Flexible Hybrid Organic-Inorganic Perovskite Resistive Random Access Memories by Employing Multilayer Graphene Transparent Conductive Electrodes

Despite several reports on perovskite resistive random access memories (RRAMs), most of them are based on transparent conductive oxide electrodes, not suitable for high flexibility. We first employ multilayer-graphene (MLG) transparent conductive electrodes (TCEs) for flexible hybrid organic-inorganic perovskite RRAMs, showing reversible bipolar resistive switching behaviors with about 0.68 and −0.5 V as set and reset bias voltages, respectively. The low-resistance state (LRS) and high-resistance state (HRS) of the RRAMs are almost constant even by data retention, switching, and bending for >104 s, > 500 cycles, and > 1000 cycles, respectively. The I-V curve at the HRS during the set process is consistent with the Ohm’s law for small voltages, but is well described by the space-charge-limited conduction mechanism for large voltages. The Ohmic conduction is also observed at the LRS during the set process. These behaviors are similarly repeated during the reset process, and well explained based on defect migration and charge trapping. These results suggest that perovskite RRAMs can be remarkably stable enough for practical applications by employing MLG TCEs.

Microstructure evolution characteristics induced by oxygen vacancy generation in anatase TiO2 based resistive switching devices

In this work, first principle calculations are employed to study the microstructure characteristics of the anatase TiO2 resistive switching material associated with the generation of oxygen vacancy (Vo) based nanofilaments during the switching process. The calculations indicate that both the magnéli phase Ti4O7 and Vo-defect phase of anatase TiO2 may be formed with the generation of oxygen vacancies during the forming and SET processes. Based on the calculations, a new physical insight is proposed to clarify the microstructure evolution characteristics of the anatase TiO2 resistive switching material and the correlation with resistive switching behaviors. During the forming or SET process, the anatase TiO2 is first excited to a transition state with the generation of oxygen vacancies, then fully relaxes to a stable Vo-defect state. This Vo-defect state may either recover to the original state with the recombination of the oxygen vacancies, which causes the reversible resistive switching behavior, or further transform to a much more stable state—the magnéli phase Ti4O7, through a phase transition process with the generation of many more oxygen vacancies. The phase transition from Vo- defective anatase phase to magnéli phase Ti4O7 causes the failure of the resistive switching due to the significantly reduced possibility of the reversible phase transition from the magnéli phase to the anatase phase, compared with the possibility of the recombination from the Vo-defective anatase.