Good Cycling Endurance Research Articles

Robust Threshold-Switching Behavior Assisted by Cu Migration in a Ferroionic CuInP2S6 Heterostructure.

The two-dimensional layered material CuInP2S6 (CIPS) has attracted significant research attention due to its nontrivial physical properties, including room-temperature ferroelectricity at the ultrathin limit and substantial ionic conductivity. Despite many efforts to control its ionic conductance and develop electronic devices, such as memristors, improving the stability of these devices remains a challenge. This work presents a highly stable threshold-switching device based on the Cu/CIPS/graphene heterostructure, achieved after a comprehensive investigation of the activation of Cu's ionic conductivity. The device exhibits exceptional threshold-switching performance, including good cycling endurance, a high on/off ratio of up to 104, low operation voltages, and an ultrasmall subthreshold swing of less than 1.8 mV/decade for the resistance-switching process. Through temperature-dependent electrical and Raman spectroscopy measurements, the stable resistive-switching mechanism is interpreted with a drifting and diffusion model of Cu ions under the electric field, rather than the conventional conducting filament mechanism. These results make the layered ferroionic CIPS material a promising candidate for information storage devices, demonstrating a compelling approach to achieving high-performance threshold-switching memristor devices.

Exploring conductance modulation and implementation of convolutional neural network in Pt/ZnO/Al2O3/TaN memristors for brain-inspired computing

Oxide-based memristors have emerged as a promising electronic device for high-density memory and neuromorphic applications. In our study, we explored the tunable analog switching and biological synaptic functions of a Pt/ZnO/Al2O3/TaN memristive device. Using transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS), we confirmed the presence of a TaOxNy interface layer at the anode contact, believed to play a critical role in resistance transitions. The memristive device showed excellent performance, including a stable and reproducible analog switching memory with a low operating voltage (μ=̶2.0/+1.7V), good cycling endurance (2 × 102), a high on/off ratio (>103), and retention up to 104 s at 85 °C. Additionally, multi-state resistances were achieved by varying the reset voltage, enabling the creation of neuromorphic synapses and high-density memories. Direct-current mode set and reset transitions showed multi-state resistance changes similar to potentiation and depression behaviors in biological synapses. Further simulations, including long-term potentiation (LTP) and long-term depression (LTD), paired pulse facilitation (PPF), and convolutional neural network (CNN) simulations for handwritten digits, showed an accuracy of 86.5%. These results indicate that the memristive device is highly suitable for use in high-density memory and brain-inspired computer systems.

Ultrahigh overall-performance phase-change memory by yttrium dragging

Benefiting from the dragging effect of yttrium, an ultrahigh overall-performance phase-change memory is reported, including low resistance drift, high data retention, low power consumption, fast operating speed, and good cycling endurance.

Self-selective analogue FeOx-based memristor induced by the electron transport in the defect energy level

A Fe2O3 film homojunction was orderly prepared by magnetron sputtering and a hydrothermal method. The Fe2O3 homojunction-based memristor exhibits an obvious self-selective effect as well as a typical analogue resistive switching (RS) memory behavior. A desirable self-rectifying voltage range (−1 to 1 V), stable resistance ratio, good cycling endurance (>104 cycles), and long retention time (>104 s) can be obtained from the Fe2O3 homojunction-based memristor. Oxygen vacancies (Vo) are inevitably generated during the growth of the Fe2O3 film. The self-selective analogue RS memory behavior is ascribed to the electron tunneling behavior between the potential barrier generated by the FeOx contact and the electron filling dynamic in the Vo-based traps. This work provides a simple method to prepare a self-selective analogue memristor and lays the foundation for the core device of neuromorphic computing.

Screening of 193i and EUV lithography process options for STT-MRAM orthogonal array MTJ pillars

Spin-transfer torque magnetic random-access memory (STT-MRAM) is considered as the most promising candidate to replace the complementary metal-oxide-semiconductor (CMOS) based memories that are dominating the market in the last few decades. What makes STT-MRAM superior to other memories is the high read and write speeds, non-volatility, good cycling endurance and near-zero leakage. Moreover, with the perpendicular device topology and the single transistor cell configuration, it becomes a very promising candidate for further device scaling which is essential to increase the memory densities. This paper focuses on the experiments performed using different lithography approaches in order to explore the smallest printable pitches for orthogonal array magnetic tunnel junction (MTJ) pillars, which are the main components of the STT-MRAM. Considering the high impact of the MTJ patterning process on the robustness of the memory device, several post-litho performance parameters such as wafer critical dimension uniformity (WCDU), local critical dimension uniformity (LCDU) and pillar circularity have also been measured and compared.

Controlling filament growth mode in resistive random-access memory based on thermal flow

To use resistive random-access memory (ReRAM) in various attractive applications, the guidelines of the device structure are required for controlling memory characteristics. In this study, 3D simulation of oxygen vacancy (VO) diffusion was performed by adopting a combination of Soret and Fick diffusions as driving forces of VOs in NiO layers of Me/NiO/Me devices (Me = Pt, Ru, W). It was demonstrated that the reciprocating motion of VOs, accompanying resistive switching, could be reproduced consistently with good cycling endurance for unipolar-type ReRAM. Furthermore, our simulation revealed that the thermal flow from the NiO layer to the electrode (EL) caused VO migration in the vertical direction, and affected both SET and RESET switching in contrast to previous reports. Accordingly, it is clear that the three-dimensional thermal design of the device structure considering ELs is crucial for tuning memory characteristics by controlling the balance of Fick and Soret diffusions.

Reliable restriction of conductive filament in graphene oxide based RRAM devices enabled by a locally graphitized amorphous carbon layer

In this work, a locally graphitized amorphous carbon (LGAC) film was successfully prepared through catalytic graphitization process. Taking advantage of its locally conductive characteristic, we demonstrate an effective and repeatable method to improve the reliability of graphene oxide based RRAM devices. The above method is responsible for a fluctuation decrease of high/low resistance states (HRS/LRS) and SET/RESET voltage from 139.6%/76.9% to 31.4%/7.5% and 50.5%/47.7% to 7.7%/6.9%, respectively. The migration of oxygen ions during both the SET and RESET processes were well restrained within the narrow conductive areas thanks to the LGAC insertion layer. In addition, the optimized memory devices also showed pretty good cycling endurance and high temperature retention characteristics. This approach may be promising for developing reliable graphene oxide based RRAM devices.

One-step solution deposited all-inorganic perovskite CsPbBr3 film for flexible resistive switching memories

Halide perovskites have attracted a great deal of attention due to their remarkable performances in solar cells, photodetectors, lasers, light emitting diodes, and memories. However, the issue of low quality of the halide perovskite films still restricts their potential applications. Here, the all-inorganic perovskite CsPbBr3 films prepared by the one-step solution deposition method are adopted as the switching layer to fabricate the flexible resistive switching (RS) memory devices. The devices exhibit a typical bipolar RS behavior including long data retention, high ON/OFF ratio, and good cycling endurance under bending, indicating that the one-step solution deposited CsPbBr3 films are promising candidates for the RS memory devices. In addition, by controlling the compliance current and applied stop voltage, the flexible RS devices demonstrate the multilevel storage capability. This work opens up the opportunity for future flexible, high performance, and multibit storage capability RS devices based on all-inorganic perovskite CsPbBr3 films.

P-channel differential multiple-time programmable memory cells by laterally coupled floating metal gate fin field-effect transistors

In this paper, we present a new differential p-channel multiple-time programmable (MTP) memory cell that is fully compatible with advanced 16 nm CMOS fin field-effect transistors (FinFET) logic processes. This differential MTP cell stores complementary data in floating gates coupled by a slot contact structure, which make different read currents possible on a single cell. In nanoscale CMOS FinFET logic processes, the gate dielectric layer becomes too thin to retain charges inside floating gates for nonvolatile data storage. By using a differential architecture, the sensing window of the cell can be extended and maintained by an advanced blanket boost scheme. The charge retention problem in floating gate cells can be improved by periodic restoring lost charges when significant read window narrowing occurs. In addition to high programming efficiency, this p-channel MTP cells also exhibit good cycling endurance as well as disturbance immunity. The blanket boost scheme can remedy the charge loss problem under thin gate dielectrics.

Selection by current compliance of negative and positive bipolar resistive switching behaviour in ZrO2−x/ZrO2 bilayer memory

We report here a ZrO2−x/ZrO2-based bilayer resistive switching memory with unique properties that enables the selection of the switching mode by applying different electroforming current compliances. Two opposite polarity modes, positive bipolar and negative bipolar, correspond to the switching in the ZrO2 and ZrO2−x layer, respectively. The ZrO2 layer is proved to be responsible for the negative bipolar mode which is also observed in a ZrO2 single layer device. The oxygen deficient ZrO2−x layer plays the dominant role in the positive bipolar mode, which is exclusive to the bilayer memory. A systematic investigation of the ZrO2−x composition in the bilayer memory suggests that ZrO1.8 layer demonstrates optimum switching performance with low switching voltage, narrow switching voltage distribution and good cycling endurance. An excess of oxygen vacancies, beyond this composition, leads to a deterioration of switching properties. The formation and dissolution of the oxygen vacancy filament model has been proposed to explain both polarity switching behaviours and the improved properties in the bilayer positive bipolar mode are attributed to the confined oxygen vacancy filament size within the ZrO2−x layer.

Nonvolatile organic resistive switching memory based on poly(o-methoxyaniline) film

Resistive switching memories have attracted considerable attention for their potential applications in next-generation nonvolatile memory devices due to high switching speed, high volume storage, low power consumption, and non-destructive readout. In this paper, a controllable and nonvolatile rewritable bipolar organic memory based on the active poly(o-methoxyaniline) (POMA) film is demonstrated. The capacitive device structure of Al/POMA/ITO exhibits good bistable resistive switching characteristics with a high ON/OFF current ratio of ~103, low switching voltage, good cycling endurance, and long retention time of over 104s. The observed bipolar switching phenomena could be elucidated by the formation and annihilation of conductive filaments, which corresponded to oxidation and reduction of metal Al top electrode and/or POMA polymer molecule chains.

Modeling of conducting bridge evolution in bipolar vanadium oxide-based resistive switching memory

We investigate the resistive switching characteristics of a Cu/VOx/W structure. The VOx film is deposited by radio-frequency magnetron sputtering on the Cu electrode as a dielectric layer. The prepared VOx sample structure shows reproducible bipolar resistive switching characteristics with ultra-low switching voltage and good cycling endurance. A modified physical model is proposed to elucidate the typical switching behavior of the vanadium oxide-based resistive switching memory with a sudden resistance transition, and the self-saturation of reset current as a function of compliance current is observed in the test, which is attributed to the growth pattern of the conducting filaments. Additionally, the related conducting mechanism is discussed in detail.

Characteristics and mechanism of nano‐polycrystalline La2O3 thin‐film resistance switching memory

AbstractWe investigated the characteristics and the mechanism of Pt/La2O3/Pt resistance switching memory with a set of measurements. The La2O3 films were determined as nano‐poly‐crystalline (diameter of the nanocrystals 5–10 nm) by XRD and HRTEM analysis. The Pt/La2O3/Pt device exhibited excellent resistive switching properties, including low switching voltage (<2 V), large low/high resistance ratio (>108), and good cycling endurance property. The conduction mecha‐ nisms of the Pt/La2O3/Pt device were revealed with current–voltage characteristics, which are different in the low and high resistance states. Furthermore, XPS analysis and temperature‐dependent resistance measurement in the low resistance state showed that the conducting filaments in the Pt/La2O3/Pt device are mainly affected by oxygen defects rather than metallic La. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Resistive switching characteristics and mechanism of thermally grown WOx thin films

Resistive switching characteristics of thermally oxidized tungsten thin films and their switching mechanism were investigated, modifying thickness of the active layer (WOx) by varying oxidation conditions. Two types of switching were observed in Pt/WOx/W memory devices. Thinner film (t ≤ 15 nm) exhibits clockwise switching (CWS) with filamentary characteristics, whereas thicker film (t ≥ 25 nm) exhibits counter-clockwise switching (CCWS) with more homogeneous conduction. Both switching modes are highly reliable and show good cycling endurance. The conduction phenomena in two different switching modes were examined. In the case of CWS, the conduction mechanism changes from Schottky emission to ohmic conduction due to the local bypass of Schottky barrier formed at Pt/WOx interface by oxygen vacancies. Contrary to CWS, CCWS showed a completely different conduction mechanism. The high resistance state is dominated by the Schottky emission at low electric field and by Poole–Frenkel emission at high electric field, whereas the low resistance state exhibits the Schottky emission. Different types of switching behavior might be attributed to the non-homogenous defect distribution across the active layer. A possible conduction sketch for two types switching behaviors is also discussed.

Improved Resistive Switching Properties of Solution Processed TiO[sub 2] Thin Films

Resistive switching characteristics of low temperature sol-gel processed (250°C) TiO 2 thin films are investigated. The Pt/TiO 2 /Pt device exhibits bipolar switching with a uniform high resistance state compared to the low resistance state. Reliability and stability of the device is significantly improved by choosing a proper compliance current in the first set operation. The film shows excellent switching properties such as high on/off ratio ( > 20), good cycling endurance, and long retention ( > 10 4 s) at 85°C. The enhanced switching properties are explained by a physical model based on localized generation/recovery of oxygen vacancy defects near the bottom electrode interface.

Embedded TFT nand-Type Nonvolatile Memory in Panel

A new NAND-type nonvolatile memory with a field-enhancing tip structure embedded in low-temperature polycrystalline silicon (LTPS) panel was demonstrated on a glass substrate for the first time. A thin-film transistor (TFT) metal-oxide-nitride-oxide-silicon (MONOS) device based on sequential lateral solidification crystallization with a fully depleted poly-Si channel, an oxide-nitride-oxide stack gate dielectric, and a metal gate is integrated into a NAND array. A NAND test array based on p-channel LTPS TFTs exhibits good cycling endurance and data retention properties and negligible program and read disturbance. These results strongly support the claim that this TFT-MONOS device is a promising candidate for use in embedded nonvolatile memory for system-on-panel and 3-D IC applications

Hybrid silicon nanocrystal silicon nitride dynamic random access memory

This paper introduces a silicon nanocrystal-silicon nitride hybrid single transistor cell for potential dynamic RAM (DRAM) applications that stores charge in silicon nanocrystals or a silicon nitride charge trapping layer or both. The memory operates in the direct tunneling regime for the tunnel oxide and so presents the possibility of a DRAM with good cycling endurance. The silicon nanocrystals of this hybrid device present intermediate states that facilitate tunneling transport to and from the nitride layer. Short time measurements show that the hybrid silicon nanocrystal silicon nitride based DRAM cell programs and erases much faster than a plain SONOS implementation while offering better data retention, memory signal and longer refresh time than a silicon nanocrystal type DRAM.