Resistive Switching Memory Research Articles

High endurance organic resistive switching memory based on 1, 2-dicyanobenzene and polymer composites

As the emerging data storage technology, organic resistive switching memory (ORSM) possesses numerous superiorities as the substitution for or the complementation of the traditional Si-based semiconductor memory. Poly(3-hexylthiophene) (P3HT) has been widely used as a polymer donor component of ORSMs due to its advantages of high mobility and high chemical stability. Up to now, ORSM based on P3HT has achieved high on/off current ratio (<i>I</i><sub>on/off</sub>), but the endurance still needs to be improved. Herein, high endurance ORSMs based on 1,2-dicyanobenzene (O-DCB) and P3HT composite are fabricated by spin coating and thermally evaporating, and exhibit non-volatile and bipolar memory characteristics. The ORSMs based on P3HT:15 wt.% O-DCB and P3HT:30 wt.% O-DCB exhibit the values of <i>I</i><sub>on/off</sub> exceeding 10<sup>4</sup> and 10<sup>3</sup> respectively, and both of them exert excellent endurance of 400 times, retention time of more than 10<sup>5</sup> s. The mechanism of the switching is explored by linear fitting of <i>I-V</i> curve and electrochemical impedance spectrum . The results indicate that the filling and vacant process of the charge traps induced by O-DCB and the inherent traps in P3HT bulk lead to a resistive switching effect. The negative or positive bias triggers off trapping and detrapping process, which leads the conductive way of charges to change, resulting in the resistive switching effect. The excellent endurance of ORSM is attributed to the uniform distribution of O-DCB in P3HT bulk because of the small molecular size and high solubility of O-DCB, resulting in well-distributed and stable charge traps. On the other hand, the out-bound planarity of O-DCB molecular promotes the close interaction with the conjugated chains of P3HT. This study enlightens an effective strategy to carry out high-endurance ORSM and facilitates their electronic applications in future.

Interface roughness effects and relaxation dynamics of an amorphous semiconductor oxide-based analog resistance switching memory.

The analog resistive switching properties of amorphous InGaZnOx (a-IGZO)-based devices with Al as the top and bottom electrodes and an Al-Ox interface layer inserted on the bottom electrode are presented here. The influence of the electrode deposition rate on the surface roughness was established and proposed as the cause of the observed unusual anomalous switching effects. The DC electrical characterization of the optimized Al/a-IGZO/AlOx/Al devices revealed an analog resistive switching with a satisfactory value for retention levels, but the endurance was found to decrease after 200 cycles. The predominant conduction mechanism in these devices was found to be thermionic emission. An in-depth analysis was performed to explore the relaxation kinetics of the device and it was found that the current has a lower decay rate. The current level stability was tested and found reliable even after 5 h. The cost-effective and precious metal-free nature of the a-IGZO memristor investigated in this study makes it a highly desirable candidate for neuromorphic computing applications.

2023: Year of Re‐Debut

2023: Year of Re‐Debut

Hexagonal Boron Nitride for Next-Generation Photonics and Electronics.

Hexagonal boron nitride (h-BN), an insulating 2D layered material, has recently attracted tremendous interest motivated by the extraordinary properties it shows across the fields of optoelectronics, quantum optics, and electronics, being exotic material platforms for various applications. At an early stage of h-BN research, it isexplored as an ideal substrate and insulating layers for other 2D materials due to its atomically flat surface that is free of dangling bonds and charged impurities, and its high thermal conductivity. Recent discoveries of structural and optical properties of h-BN have expanded potential applications into emerging electronics and photonics fields. h-BN shows a very efficient deep-ultraviolet band-edge emission despite its indirect-bandgap nature, as well as stable room-temperature single-photon emission over a wide wavelength range, showing a great potential for next-generation photonics. In addition, h-BN is extensively being adopted as active media for low-energy electronics, including nonvolatile resistive switching memory, radio-frequency devices, and low-dielectric-constant materials for next-generation electronics.

Multifunctional polyimides for resistive switching memory devices based on flexible transparent polyimide–silver nanowires hybrid electrodes

AbstractWith the quick development of flexible memory electronics, multifunctional organic materials have been the necessary for fabricating electronics. In this work, the highly transparent and flexible electrode was successfully prepared by coating the high‐performance silver nanowires (AgNWs) onto the colorless polyimide (PI) substrate. The prepared flexible PI–AgNWs electrodes exhibited a relatively low sheet resistance of 15 Ω/sq with the high transparency of 68% at the wavelength of 400 nm. A novel kind of polyimide TPC6FPI was successfully synthesized and characterized with the excellent thermostability and high glass transition temperature (Tg) above 250°C. Furthermore, a kind of flexible transparent PI–AgNWs/TPC6FPI/Al resistive memory device was prepared and exhibited good SRAM switching behavior with the threshold voltage of around 2.1 V and the ON/OFF current ratio of ˜104, which indicated that multifunctional PI‐based memory device showed the potential to the wearable devices.

Tracing the Si Dangling Bond Nanopathway Evolution ina-SiNx:H Resistive Switching Memory by the Transient Current

With the big data and artificial intelligence era coming, SiNx-based resistive random-access memories (RRAM) with controllable conductive nanopathways have a significant application in neuromorphic computing, which is similar to the tunable weight of biological synapses. However, an effective way to detect the components of conductive tunable nanopathways in a-SiNx:H RRAM has been a challenge with the thickness down-scaling to nanoscale during resistive switching. For the first time, we report the evolution of a Si dangling bond nanopathway in a-SiNx:H resistive switching memory can be traced by the transient current at different resistance states. The number of Si dangling bonds in the conducting nanopathway for all resistive switching states can be estimated through the transient current based on the tunneling front model. Our discovery of transient current induced by the Si dangling bonds in the a-SiNx:H resistive switching device provides a new way to gain insight into the resistive switching mechanism of the a-SiNx:H RRAM in nanoscale.

Resistive Switching Memory Cell Property Improvement by Al/SrZrTiO3/Al/SrZrTiO3/ITO with Embedded Al Layer.

The SrZrTiO3 (SZT) thin film prepared by sol-gel process for the insulator of resistive random-access memory (RRAM) is presented. Al was embedded in the SZT thin film to enhance the switching characteristics. Compared with the pure SZT thin-film RRAM, the RRAM with the embedded Al in SZT thin film demonstrated outstanding device parameter improvements, such as a resistance ratio higher than 107, lower operation voltage (VSET = -0.8 V and VRESET = 2.05 V), uniform film, and device stability of more than 105 s. The physical properties of the SZT thin film and the embedded-Al SZT thin-film RRAM devices were probed.

Polarization retention dependence of imprint time within LiNbO3 single-crystal domain wall devices

Ferroelectric LiNbO3 single crystals have wide applications in surface acoustic wave filters, pyroelectric sensors, and electro-optic modulators. Large-area LiNbO3 single-crystal thin films integrated on silicon are promising for high density integration of ferroelectric domain-wall resistance switching memories and transistors. However, the short-time operation of the memory often suffers from poor polarization retention due to the built-in imprint voltage. Here, we observed the strong polarization orientation-dependent imprint effect within either out-of-plane or in-plane LiNbO3 thin-film capacitors. The imprint effect can shift domain switching hysteresis loops toward positive/negative voltages seriously with written negative/positive polarizations that occur within a characteristic imprint time of 5.1 ms–360 s. Once the write time of the memory is shorter than the imprint time, the inverted domain is unstable and switches back into its previous orientation automatically after the termination of a write operation. However, the write failure can be avoided if the write time is longer than the imprint time, and the written domain can be deeply protected by the imprint field. A model of polarization-dependent charge injection at the interface is developed to explain the time-dependent imprint effect. For a mesa-like LiNbO3 memory cell in contact with two side electrodes fabricated at the film surface, the imprint time can be greatly shortened below 30 ns with the extension of one side electrode over the cell surface to screen the tail of the switched domain, enabling ferroelectric domain-wall resistance switching devices in excellent retention and high operation speeds.

Spray deposition of the nanostructured ZnO thin films for non-volatile resistive switching memory applications

Spray deposition of the nanostructured ZnO thin films for non-volatile resistive switching memory applications

Dimer-type Cs3Sb2I9: An efficient perovskite material for low operating voltage and high stability flexible resistive switching memory

All-inorganic perovskites have been taken as the promising functional materials in non-volatile resistive switching (RS) memory. Herein, the lead-free all-inorganic Cs3Sb2I9 perovskites with high stability are fabricated via hydrochloric acid (HCl) assisted solution method at low-temperature. The devices with a structure of Ag/polymethyl methacrylate (PMMA)/HCl-modified dimer-Cs3Sb2I9/ITO take on typical bipolar RS behavior and remarkable characteristics such as high ON/OFF ratio (≈66), low operating voltage (≈ −0.34 V/+0.25 V), excellent endurance property (≥120 cycles) and long data retention (≥104 s). Moreover, outstanding mechanical stability of the Cs3Sb2I9-based flexible memory devices are demonstrated under different bending angles and over consecutive 103 bending cycles. In addition, the Cs3Sb2I9-based memory devices show no obvious change in the RS behavior after over 10 days storage under an ambient atmosphere. This work will contribute to understanding the characteristics of low operating voltage and high stability RS behavior of the all-inorganic perovskites, and illuminate the great application potential of the lead-free antimony-based perovskite materials in next generation low power consumption non-volatile flexible memory devices.

Stacked One‐Selector‐One‐Resistive Memory Crossbar Array With High Nonlinearity and On‐Current Density for the Neuromorphic Applications (Adv. Electron. Mater. 12/2022)

Resistive Switching Memory The RuO2 electrode is used to suppress the selector degradation during the switching operation. The one selector-one resistive switching memory (1S1R) array using the selector with superior performance is fabricated to implement a hardware neural network. 1S1R effectively suppress sneak current through high nonlinearity of the selector. Three simple alphabets, “L”, “I”, and “X” are classified through the 1S1R array, and the proposed 1S1R device shows possibilities for neuromorphic applications. More details can be found in article number 2200656 by Cheol Seong Hwang and co-workers.

Advances in flexible non-volatile resistive switching memory based on organic poly (3, 4-ethylenedioxythio phene): Poly (styrenesulfonate) film

In this work, the resistive switching memory has been investigated in conducting polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) with aluminium (Al) and indium tin oxide (ITO) acting as electrodes. Current-voltage (I-V) characteristics of the fabricated Al/PEDOT:PSS/ITO flexible Polyethylene terephthalate substrate device reveal a non-volatile resistive switching behaviour. The memory device demonstrates resistive switching non-volatile memory with ION/IOFF current ratio between the high resistance state (HRS) and low resistance state (LRS) up to 104. Both the HRS and LRS of the memory devices are stable, showing no significant change in value of ION/IOFF current ratio, which is maintained at 104 in magnitude under continuous read-out testing for 100 cycles at 90º bending angle, and also retention time of 33 min that confirms the device durability and non-volatility. The charge transport mechanism of the fabricated non-volatile organic devices is governed by space-charge limited conduction. It is proposed that the reduction and oxidation of PEDOT:PSS film might be the switching mechanism. Interestingly, the performance of the memory device revealed no detectable degradation and remained identical even after bending the device from 70 to 160° angles, representing excellent flexibility. Besides, the lowest power and the critical compliant current for resistive switching are determined. The power density for 180° (without bending), 160°, 90° and 70° bending angles is ∼ 30 Wm−2. It demonstrates that for a small range of compliance current, our device showed more power capacity with lower voltage consumption, which makes it a potential candidate for low power consumption flexible non-volatile memory devices.

Enhanced Resistive Switching Performance through Air-Stable Cu2AgSbI6 Thin Films for Flexible and Multilevel Storage Application.

Herein, the lead-free halide perovskite films with different Cu-to-Ag ratios (Cu3-xAgxSbI6, x = 0, 1, 2, or 3) have been prepared by a spin-coating method at low temperature. The enhanced resistive switching (RS) performance of more uniform SET/RESET voltages and the endurance up to at least 1600 cycles are found in the RS memory with a device structure of Ag/PMMA/Cu2AgSbI6/ITO. The device performance is not degraded under different bending angles and after 103 bending cycles, which is beneficial for flexible memory applications. The appropriately increased activation energy of the perovskites with the partial substitution of Ag atoms, which would lead to a more robust filament formed, is proposed to explain the enhanced RS mechanism. Importantly, the effective size and number of filaments measured by conductive AFM are introduced to confirm the multilevel storage effect of Cu2AgSbI6. The multilevel storage characteristics with four resistance levels are demonstrated by various compliance currents. Moreover, the Cu2AgSbI6 memory devices still exhibit enhanced RS properties and multilevel storage after 75 days of exposure to ambient conditions. Our study provides a strategy for improving the stability and high-density storage applications of halide perovskite RS memory devices.

Atomic-scale observation of strain-dependent reversible topotactic transition in La0.7Sr0.3MnOx films under an ultra-high vacuum environment

Reversible topotactic phase transition between perovskite (PV) and oxygen-vacancy-ordered brownmillerite (BM) structures provides an effective platform for realizing the control of physical properties in complex transition metal oxides. However, such reversibility always requires extreme external conditions, that is, a high temperature and vacuum environment during the PV-BM transition, while an oxidizing atmosphere and relatively low temperature vice versa. Here, we experimentally observe the reversible process in strained La0.7Sr0.3MnOx films at atomic scale by using in-situ heating aberration-corrected scanning transmission electron microscopy (STEM). Apart from the conventional reduction reaction of creating oxygen-vacancy-ordered frameworks after heating in the TEM, the inverse process of BM-to-PV transition is unexpectedly discovered under such an ultra-high vacuum atmosphere (∼10−9 Torr) at room temperature. Moreover, this abnormal behavior is strain-dependent. The large compressive strain is found to be detrimental to the inverse phase transition. The density functional theory (DFT) calculations show that the high oxygen affinity of La0.7Sr0.3MnO2.5 is responsible for the reversible transitions. Our findings provide a new insight into the redox reactions of manganite and might be further utilized for potential applications in solid fuel cells, oxygen sensors or resistive switching memories.

Improved Performance of the Al2O3-Protected HfO2-TiO2 Base Layer with a Self-Assembled CH3NH3PbI3 Heterostructure for Extremely Low Operating Voltage and Stable Filament Formation in Nonvolatile Resistive Switching Memory.

Herein, we report intriguing observations of an extremely stable nonvolatile bipolar resistive switching (NVBRS) memory device fabricated using HfO2-TiO2 topologically protected by Al2O3 as a stacked base layer for a CH3NH3PbI3 (MAPI) electrolyte layer sandwiched between Ag and fluorine-doped tin oxide (FTO) electrodes. MAPI has been successfully synthesized by a rapid microwave-solvothermal (MW-ST) method within 10 min at 120 °C without requiring any inert gas atmosphere using low-cost precursors and solvents. Subsequently, MAPI powders are dissolved in aprotic solvents (DMF/DMSO = 8:2), and a spin-coated thin film is allowed to recrystallize upon annealing at 120 °C via a solution-based nanoscale self-assembly process. The fabricated memory device with the Ag/MAPI/Al2O3/TiO2-HfO2/FTO configuration shows an enhanced resistance ratio of 105 for >104 s at an extremely lower operating voltage (SET +0.2 V, RESET -0.2 V) when compared to that of the pristine MAPI device (±1 V, 102, 104 s). We show that the memory device also exhibits a remarkable endurance of ≥3500 cycles due to the Al2O3 robust coating on the HfO2-TiO2 layer, facilitating prompt heterojunction formation. Thus, the adopted innovative strategies to prepare structurally and optically stable (∼1.5 years) MAPI under high-humid conditions could offer enhanced performance of NVBRS memory devices for medical, security, internet of things (IoT), and artificial intelligence (AI) applications.

Effect of Temperature on Analog Memristor in Neuromorphic Computing

In this article, the influence of the temperature instability of resistive memory switching on potential neuromorphic computing applications is extensively studied using an Intel TaOx-based analog-type memristor as a synaptic weight modulator in a neural network. Evaluation results show that the effect of ambient temperature during training and interference can degrade the neural network’s accuracy due to inefficient weight updates and inevitable resistance or conductance drifting. Our results provide additional insights into device-level physical models and simple circuit-level design guidance for potential hardware-based neuromorphic computing applications.

Synaptic Device based on Resistive Switching Memory using Single-walled Carbon Nanotubes

Recently, research has been conducted on a biomimetic system called artificial neural networks (ANNs) to overcome the limits of Von Neumann’s system. Spiking neural networks (SNNs) in ANNs are hardware systems that implement NNs’ low-power parallel processing. The electrical characteristics of synaptic devices, which affect learning and memory, are important in SNN construction. Synaptic devices based on resistive switching are called memristors and have sufficient learning capabilities, such as spike-timing-dependent plasticity gradual switching [1]. However, memristors require high switching voltages and currents, resulting in high power consumption. To reduce the operation voltage of the synapse, new materials must be developed for the switching oxide and metal electrode. The conventional memristor structure comprises metal-oxide-metal (MOM) or metal-oxide-N+Si (MOS). This study proposes a synaptic device with single-walled carbon nanotubes (SWCNTs) with excellent electrical and mechanical properties to lower the switching voltage and fabricate a metal-oxide-SWCNTs-N+Si (MOCS)-structured synaptic device using SWCNTs as a metal electrode, as shown in Fig. 1 [2]. Finally, the electrical characteristics of MOM, MOS, and MOCS structures are analyzed and compared.

Recent Advances in Halide Perovskite Resistive Switching Memory Devices: A Transformation from Lead-Based to Lead-Free Perovskites.

Due to their remarkable electrical and light absorption characteristics, hybrid organic-inorganic perovskites have recently gained popularity in several applications such as optoelectronics, lasers, and light-emitting diodes. Through this, there has recently been an increase in the use of halide perovskites (HPs) in resistive switching (RS) devices. However, lead-based (Pb-based) perovskites are notorious for being unstable and harmful to the environment. As a result, lead-free (Pb-free) perovskite alternatives are being investigated in achieving the long-term and sustainable use of RS devices. This work describes the characteristics of Pb-based and Pb-free perovskite RS devices. It also presents the recent advancements of HP RS devices, including the selection strategies of perovskite structures. In terms of resistive qualities, the directions of both HPs appear to be identical. Following that, the possible impact of switching from Pb-based to Pb-free HPs is examined to determine the requirement in RS devices. Finally, this work discusses the opportunities and challenges of HP RS devices in creating a stable, efficient, and sustainable memory storage technology.

Resistive switching of two-dimensional NiAl-layered double hydroxides and memory logical functions

Two-dimensional NiAl layered double hydroxides (LDHs) were synthesized by urea hydrolysis method. Considering its unique layered structure and high-speed carrier transfer channel, NiAl-LDHs were applied to the active layer of memristor through spin coating process. It is found that the Al/NiAl-LDHs/Al memristor exhibits unipolar resistance switching characteristics, which resistive switching mechanism is attributed to formation and fusing of conductive filaments controlled by oxygen vacancies. Based on this Al/NiAl-LDHs/Al memristor, a D-type latch was constructed. A memtransistor with Si/SiO2/graphene oxide (GO)/Al/NiAl-LDHs/Al structure was built by connecting Al/NiAl-LDHs/Al memristor in series on the drain electrode of GO transistor. The memtransistor exhibits excellent gate controllability and resistive switching characteristics. Combined with its characteristics, we used the memtransistor to build a D-trigger and verify its memory logical function. The result shows the great potential of layered bimetallic hydroxide materials in the field of resistance switching memory and memory computing.

Biomaterial-based nonvolatile photonic memory

The emerging optoelectronic resistive switching memory are more attractive owing to their ability to combine the advantages of both photonics and electronics. However, currently proposed optoelectronic resistive switching memory are light erasing/writing only or photo-induced modulated. In this research, we report the optoelectronic resistive switching memory composed of a simple ITO/NiO nanoparticles-apple pectin (AP NiO)/Al structure. Due to the detraping/retrapping of electrons within the AP NiO layer, which effectively modulates the band bending at the Al/AP NiO region, thus leading to persistent photoresponse in the present devices. The results of using electrical writing and UV light writing exhibited different current transmission mechanisms, clearly confirming the uniqueness of the light-writing behavior. In addition, light erasing can be achieved during green light irradiation with a wavelength. Results on the correlation of the light writing/erasing with the transmission mechanisms will also be explored. The transmission mechanisms are summarized as follows: Type I (filament only), Type II (trap-assisted tunneling and trap–detrap domain) and Type III (hybrid path). The measurements of CAFM are particularly useful for construction of the mechanical model. Exploiting the dependence of different mechanism on the light writing/erasing may enable new design space for future bio-electronic applications.