Self-rectifying Resistive Switching Research Articles

Self-rectifying resistive switching in MAPbI3-based memristor device

A critical stage in developing high-density memristors is addressing the sneak current within the crossbar architecture. One of the effective strategies to endow the memristive cell with the ability to prevent sneak currents when it is in a low resistance state is to give it an inherent diode, known as a self-rectifying memristive cell. This study demonstrates the Schottky diode inside the MAPbI3-based memristive cell, a consequence of its interaction with the tungsten (W) electrode. The performance of memory devices is reliable with low-voltage operation, a resistance window having over ten of magnitude, and the retention time remains over 104 s. Prominently, the self-rectifying behavior is sustainable over 150 cycles and exhibits a rectification ratio of approximately 102 times. Density functional theory calculation reveals the presence of unoccupied gap states on an interfaced MAPbI3 surface, serving as electron trapping states during the charge transport across the W/MAPbI3 Schottky interface. Consequently, the conduction mechanism is primarily governed by an interfacial-controlled model, notably Schottky emission. This improvement promises to eliminate sneak currents in future crossbar array fabrication.

Self-Rectifying Resistive Switching Memory Based on Molybdenum Disulfide for Reduction of Leakage Current in Synapse Arrays

Resistive random-access memory has emerged as a promising non-volatile memory technology, receiving substantial attention due to its potential for high operational performance, low power consumption, temperature robustness, and scalability. Two-dimensional nanostructured materials play a pivotal role in RRAM devices, offering enhanced electrical properties and physical attributes, which contribute to overall device improvement. In this study, the self-rectifying switching behavior in RRAM devices is analyzed based on molybdenum disulfide nanocomposites decorated with Pd on SiO2/Si substrates. The switching layer integration of Pd and MoS2 at the nanoscale effectively mitigates leakage currents decreasing from cross-talk in the RRAM array, eliminating the need for a separate selector device. The successful demonstration of the expected RRAM switching operation and low switching dispersion follows the application of a Pd nanoparticle embedding method. The switching channel layer is presented as an independent (Pd nanoparticle coating and MoS2 nanosheet) nanocomposite. The switching layer length (4000 μm) and width (7000 μm) play an important role in a lateral-conductive-filament-based RRAM device. Through the bipolar switching behavior extraction of RRAM, the formation of the conductive bridges via electronic migration is explained. The fabricated Pd-MoS2 synaptic RRAM device results in a high resistive current ratio for a forward/reverse current higher than 60 at a low resistance state and observes a memory on/off ratio of 103, exhibiting stable resistance switching behavior.

Deep reservoir computing based on self-rectifying memristor synapse for time series prediction

Herein, a self-rectifying resistive switching memristor synapse with a Ta/NbOx/Pt structure was demonstrated for deep reservoir computing (RC). The memristor demonstrated stable nonlinear analog switching characteristics, with a rectification ratio of up to 1.6 × 105, good endurance, and high uniformity. Additionally, the memristor exhibited typical short-term plasticity and dynamic synaptic characteristics. Based on these characteristics, a deep memristor RC system was proposed for time series prediction. The system achieved a low normalized root mean square error (NRMSE) of 0.04 in the time series prediction of the Henon map. Even at 90 °C, deep RC retains good predictive power with an NRMSE of only 0.07. This work provides guidance for efficient deep memristive RC networks to handle more complex future temporal tasks.

The bipolar and self-rectifying resistive switching characteristics of UiO-66 modified with uric acid

The bipolar and self-rectifying resistive switching characteristics of UiO-66 modified with uric acid

Lithium incorporation enhanced resistive switching behaviors in lithium lanthanum titanium oxide-based heterostructure

• Self-rectifying resistive switching device based on lithium lanthanum titanium oxide. • The simplified device has a high rectification ratio and on/off ratio. • Schottky barrier assisted model explains the electronic bipolar resistive switching. • Li + migration accelerates electron injection and enhances the performance of the device. Resistive switching devices with a high self-rectifying ratio are important for achieving the crossbar memristor array that overcomes the sneak current issue. Herein, we demonstrate a single amorphous lithium lanthanum titanium oxide (LLTO) layer based Pt/LLTO/Pt device possessing a self-rectifying ratio higher than 1 × 10 4 that is comparable to the reported devices with complicated multi-layer stacking structures. Moreover, the device shows forming-free and highly uniform bipolar resistive switching (BRS) characteristic that facilitates the potential applications. The trap-controlled and trap-free space charge limited conductions are demonstrated to dominate the high and low resistance states of the device, respectively. The fast migration of lithium ions under external voltage accelerates the electron injection across the Pt/LLTO interface and also the space charge accumulation in the LLTO layer, and as a result, the high performance of the Pt/LLTO/Pt device was achieved. As demonstrated Pt/LLTO/Pt device sheds a light on the potential applications of the lithium ionic conductors in self-rectifying resistive switching devices.

Reliable resistive switching and synaptic plasticity in Ar+-irradiated single-crystalline LiNbO3 memristor

Typical filament-type memristors suffer from temporal and spatial variations in the resistive switching due to stochastic filament formation, which hinders the implementation of memristive synapses in neuromorphic computing. In this work, the memristor based on Ar+-irradiated single-crystalline LiNbO3 (SC-LNO) thin film is reported. The high-quality SC-LNO thin films contribute to the formation of more concentrated and robust oxygen vacancy channels (OVCs) and lead to reliable self-rectifying resistive switching behaviors with an ultra-low device-to-device variability of ∼2.80% and cycle-to-cycle variability of ∼2.25%, as well as long retention time at multilevel resistance states (>3 × 104 s), stable endurance performance (>105 cycles), excellent environmental stability (>6 months), and good analog switching linearity. Furthermore, abundant synaptic plasticity characteristics including paired-pulse facilitation (PPF), post-tetanic potentiation (PTP), long-term potentiation (LTP), long-term depression (LTD), spike-timing-dependent plasticity (STDP), and associative learning, are also successfully emulated using this device as an electronic synapse. The spontaneous decay process right after applied voltage pulses and the long-term nonvolatility characteristics in Ar+-irradiated SC-LNO memristor indicate the existence of residual OVCs, which serves to guide the reconstruction of OVCs during repeated switching and to further enhances the uniformity of device switching characteristics.

Analog-to-digital and self-rectifying resistive switching behavior based on flower-like δ-MnO2

Memristors can be divided into two types, analog and digital, according to the characteristics of current gradients and sudden changes. It is particularly important to realize analog and digital switching behaviors in the same device to facilitate the development of analog–digital circuits. In this work, the flower-like δ-MnO2 was prepared on fluorine doped tin oxide (FTO) substrate by chemical bath deposition method, and it can be used as dielectric layer of memristor. Analog and digital types of resistive switching behaviors were achieved in the same device with Ag/δ-MnO2/FTO structure by adjusting the applied voltage range on top electrode of memristor. Moreover, the digital type of resistive switching behavior with multi-level and self-rectifying properties was realized in this device. The charge transport and resistive switching mechanism of the device with analog to multi-level self-rectifying digital types was explained by analyze its current–voltage (I-V) curve. Therefore, this new type of memristive device with both analog and digital properties can simplify the circuit complexity, and the multilevel and self-rectification behavior can greatly improve the storage density and solve the misreading problem of memristive devices.

Self-rectifying and forming-free resistive switching behaviors in Pt/La2Ti2O7/Pt structure

In this work, we report the resistive switching behavior of an amorphous La2Ti2O7 (LTO) film as sandwiched between two Pt electrodes. The resistive switching is forming-free and highly uniform. Furthermore, it exhibits self-rectifying resistive switching behaviors owing to the Schottky contact and quasi-ohmic contact formed at the top and bottom interfaces, respectively. The mechanism of switching behavior in the device is attributed to the trapping/detrapping-mediated electronic bipolar resistance switching. By fitting the current-voltage characteristics, it indicates the coexistent conduction mechanisms of Schottky emission and space-charge-limited-conduction (SCLC), while the Schottky barrier modified by electron trapping/detrapping plays a dominating role in the resistive switching process.

A nonlinear resistive switching behaviors of Ni/HfO2/TiN memory structures for self-rectifying resistive switching memory

This work reports forming free/self-rectifying resistive switching characteristics and dependency of the top electrode (TE) of a crystalline HfO2-based resistive switching memory device. In the memory cells, nonlinear bipolar resistive switching characteristics, i.e., an asymmetric current-voltage curve like the Schottky diode, was observed. In addition, the device exhibits resistive switching behaviors without forming process, which makes it possible to switch the resistance state under ultra-low current levels of <10 nA. In addition, compared to the resistive switching of the proposed resistive switching memory devices with different TEs, the VSET was decreased when using TE with lower work function, and the height read margin was obtained in the sample with the Ni TE, covering over 56 × 56 arrays. Consequently, these results indicate that the interface control resistive switching properties in memory structures having the Schottky junction warrant the realization of selector-free resistive switching memory cells in a high-density crossbar array.

Retention enhancement through capacitance-dependent voltage division analysis in 3D stackable TaOx/HfO2-based selectorless memristor

Sneak path current generated by adjacent cells in three-dimensional (3D) memristor arrays must be curbed while securing the multi-bit storage capability of each cell to aid in the cost-effective increase in array size. For this purpose, a 3D stackable TaOx/HfO2-based selectorless memristor has been proposed and optimized via capacitance-dependent voltage division analysis. The proposed device utilizes the formation or rupture of conductive filaments for self-rectifying resistive switching operation, in contrast to nonfilamentary devices that often exploit the change in the charge state of the electron trap. This approach enables the reduction of the trapped charge leakage through the interface between the resistive switching and metal layers effectively, giving rise to excellent retention properties (>5 × 105 s). Furthermore, the proposed device exhibits a sufficiently high on/off ratio (~1.35 × 103), rectification ratio (~2.3 × 103), endurance (1.5 × 102 cycles), and low resistance variation (standard deviation <0.022). Moreover, multilevel operations are facilitated, making the proposed device suitable for high-density, nonvolatile memory applications.

Self-rectifying resistive switching characteristics of Ti/Zr3N2/p-Si capacitor for array applications

In this study, we present a self-rectifying resistive switching property observed in Ti/Zr3N2/p-Si and Ti/Zr2N/p-Si metal-insulator-semiconductor (MIS) capacitors for array applications. Compared to the Zr2N film, the Zr3N2 film has a higher trap density due to weaker bonding energy and a higher trap generation rate. In the experimental results for the Zr3N2 sample, we observed a higher on/off ratio, a larger read margin, more stable retention, and more stable DC cycling. In addition, both the trap concentrations increased at the LRS compared to of the common HRS, which was a result of analyzing the nitride trap density (Nnt) within the ZrxNy film and an interface trap (Nit) between the ZrxNy and the p-Si layers. Particularly, it is found in the Zr3N2 film that the Nnt is rapidly increased, which results in an increased current ratio and an increased read margin.

Self-rectifying resistive switching phenomena observed in Ti/ZrN/Pt/p-Si structures for crossbar array memory applications

In this Letter, the self-rectifying resistive switching (RS) behavior is demonstrated in Ti/ZrN/Pt/p-Si resistive random access memory (RRAM) devices. Compared to an RS characteristic of the conventional Ti/ZrN/Pt structures, the memory cell with a p-Si bottom layer shows a larger current ratio. However, a current-limited region is also more clearly obtained in a low voltage region, which can result in one diode-type RRAM with self-selecting properties. Consequently, these results infer that the proposed ZrN-based RRAM cells with a Pt/p-Si selector warrant the realization of the self-selecting RRAM cell without any additional peripheral elements to suppress a disturbance in the reading operation.

Self-Rectifying Resistive Switching and Short-Term Memory Characteristics in Pt/HfO2/TaOx/TiN Artificial Synaptic Device.

Here, we propose a Pt/HfO2/TaOx/TiN artificial synaptic device that is an excellent candidate for artificial synapses. First, XPS analysis is conducted to provide the dielectric (HfO2/TaOx/TiN) information deposited by DC sputtering and atomic layer deposition (ALD). The self-rectifying resistive switching characteristics are achieved by the asymmetric device stack, which is an advantage of the current suppression in the crossbar array structure. The results show that the programmed data are lost over time and that the decay rate, which is verified from the retention test, can be adjusted by controlling the compliance current (CC). Based on these properties, we emulate bio-synaptic characteristics, such as short-term plasticity (STP), long-term plasticity (LTP), and paired-pulse facilitation (PPF), in the self-rectifying I–V characteristics of the Pt/HfO2/TaOx/TiN bilayer memristor device. The PPF characteristics are mimicked by replacing the bio-stimulation with the interval time of paired pulse inputs. The typical potentiation and depression are also implemented by optimizing the set and reset pulse. Finally, we demonstrate the natural depression by varying the interval time between pulse inputs.

TiO x -based self-rectifying memory device for crossbar WORM memory array applications* *Project supported by the National Natural Science Foundation of China (Grant Nos. 61774079 and 61664001), the Science and Technology Plan of Gansu Province, China (Grant No. 20JR5RA307), and the Key Research and Development Program of Gansu Province, China (Grant No. 18YF1GA088).

Resistive switching with a self-rectifying feature is one of the most effective solutions to overcome the crosstalk issue in a crossbar array. In this paper, a memory device based on Pt/TiO x /W structure with self-rectifying property is demonstrated for write-once-read-many-times (WORM) memory application. After programming, the devices exhibit excellent uniformity and keep in the low resistance state (LRS) permanently with a rectification ratio as high as 104 at ± 1 V. The self-rectifying resistive switching behavior can be attributed to the Ohmic contact at TiO x /W interface and the Schottky contact at Pt/TiO x interface. The results in this paper demonstrate the potential application of TiO x -based WORM memory device in crossbar arrays.

Facile synthesis and nanoscale related physical properties of core-shell structured CuO/ZnO nanorods on Si substrate

Core-shell structured CuO/ZnO nanorods (NRs) consisting of monocrystalline p-type CuO core covered with the nanocrystalline n-type ZnO shell were directly fabricated on Si substrate through depositing ZnO on the as-grown CuO NRs. The in-situ current-voltage (I-V) characterization of CuO/ZnO NRs by conductive atomic force microscopy (C-AFM) revealed a novel p-type based self-rectifying resistive switching behavior, providing an effective solution to suppress sneak current issue for nonvolatile memory applications. The special switching characteristic and better rectification can be explained by the asymmetric back-to-back structure of C-AFM tip/ZnO and ZnO/CuO under different electric field directions due to the special core-shell structured p-n junction. Compared with bare CuO core, the red-shift and increased photoluminescence (PL) intensity for the CuO/ZnO NRs have been attributed to the deposited shell and special heterostructure. These results demonstrated that the electrical and optical properties of CuO NRs can be successfully tuned by introducing a ZnO shell, which is important for potential applications in functional nanodevices at room temperature.

Vacancy-modulated self-rectifying characteristics of NiOx/Al2O3-based nanoscale ReRAM devices

A vacancy-modulated self-rectifying resistive random access memory (ReRAM) with a Ti/NiOx/Al2O3/Pt structure is proposed in this study. Here, NiOx is used as a resistive switching layer, and Al2O3 is used as a tunnel barrier layer for producing self-rectifying behavior. The tunnel barrier thickness in the NiOx/Al2O3 interfacial region can be increased or decreased according to the movement of oxygen vacancies in the NiOx layer under positive or negative voltages, respectively, thereby leading to self-rectifying resistive switching behavior. As a result, the NiOx/Al2O3-based self-rectifying ReRAM exhibits a low operation current of ∼3 × 10−7 A, large ON/OFF ratio of ∼6 × 103, high rectification ratio of ∼5 × 102, long retention of 105 s, and forming-free and self-compliance characteristics, meeting the next generation ReRAM requirements. The Ti/NiOx/Al2O3/Pt-based self-rectifying structures can pave the way to develop high-density embedded memory applications in the future.

Engineering of self-rectifying filamentary resistive switching in LiNbO3 single crystalline thin film via strain doping

The abilities to fabricate wafer scale single crystalline oxide thin films on metallic substrates and to locally engineer their resistive switching characteristics not only contribute to the fundamental investigations of the resistive switching mechanism but also promote the practical applications of resistive switching devices. Here, wafer scale LiNbO3 (LNO) single crystalline thin films are fabricated on Pt/SiO2/LNO substrates by ion slicing with wafer bonding. The lattice strain of the LNO single crystalline thin films can be tuned by He implantation as indicated by XRD measurements. After He implantation, the LNO single crystalline thin films show self-rectifying filamentary resistive switching behaviors, which is interpreted by a model that the local conductive filaments only connect/disconnect with the bottom interface while the top interface maintains the Schottky contact. Thanks to the homogeneous distribution of defects in single crystalline thin films, highly reproducible and uniform self-rectifying resistive switching with large on/off ratio over four order of magnitude was achieved. Multilevel resistive switching can be obtained by varying the compliance current or by using different magnitude of writing voltage.

High-performance and self-rectifying resistive random access memory based on SnO2 nanorod array: ZnO nanoparticle structure

To develop high-density memory arrays, a self-rectifying resistive random access memory based on a Cu/SnO2 nanorod array: ZnO nanoparticle (NP)/fluorine-doped tin oxide (FTO) structure is proposed to avoid the sneak current. The proposed device exhibits transparent property and significant merits including high ON/OFF ratio, conspicuous endurance and superior data retention. A carrier transport model based on a SnO2/FTO Schottky barrier, ZnO NP trap effect and Cu filament is proposed to explain the self-rectifying resistive switching performance. This work provides a new method to effectively avoid sneak current and also shows promising prospects in constructing high-performance transparent memory arrays.

Self-rectifying resistive switching behavior observed in sodium copper chlorophyllin-polyvinyl alcohol composites on a flexible and transparent substrate

Sodium copper chlorophyllin (SCC)- polyvinyl alcohol (PVA) composites thin films have been prepared on flexible and transparent ITO/PET substrates using Ag as the top electrode. FE-SEM shows that the prepared SCC-PVA thin films are smooth and dense, SCC particles have embedded in PVA and formed nano-islands, which are distributed irregularly in the thin film. The optical transmittance spectrum demonstrates that Ag/SCC-PVA/ITO/PET can be used as a transparent electronic device. I–V characteristics of the Ag/SCC-PVA/ITO/PET show that the device exhibits self-rectifying resistive switching performance, which could be related to the forming/rapture of Ag conductive filaments induced by the migration of Ag ions. This study demonstrates the potential uses of SCC-PVA in low-cost, flexible and transparent resistive switching memory.

Self-rectifying and interface-controlled resistive switching characteristics of molybdenum oxide

The self-rectifying resistive switching (RS) characteristics of molybdenum oxide (MoOx) semiconductors are investigated in this paper. The MoOx RS layers are deposited by radio-frequency sputtering. By adjusting the O2 flow rate in the sputtering process to control the oxygen vacancy content in the MoOx layer, an Al/MoOx/Pt resistive random access memory (RRAM) with significant self-rectifying characteristics can be fabricated at room temperature (RT). The effect of the electrode size on the RRAM performance is examined. Both the high resistance state (HRS) and low resistance state (LRS) resistances decrease with increasing electrode size, which indicates that the Al/MoOx/Pt RRAM follows interface-controlled switching. The physical mechanisms of the self-rectifying, RS, and carrier conduction mechanisms are studied.