Memristive Switching Behavior Research Articles

Memristive switching in Cu/Si/Pt cells and its improvement in vacuum environment

Memristive switching in materials attracts intensive attention due to its potential application for nonvolatile memories. The environmental effect on the switching stability is of crucial importance to the fabrication and performance of a real memory devices. In this work, a solid state electrochemical cell with Cu/Si/Pt sandwich structure has been investigated. The cell shows a forming-free and gradual memristive switching behavior. The environmental atmosphere has significant effect on the switching behavior. We suggest that Cu electrode is oxidized by the atmosphere, forming a CuOx layer at the Cu/Si interface. The memristive switching can be attributed to the redox reaction between the CuOx and Si layers with an equilibrium of oxygen exchange between the cell and the environment. By pre-fabricating a CuOx layer during the cell preparation, the oxygen exchange with the environmental atmosphere is avoided and the switching degradation in vacuum condition is improved. These results provide a fundamental insight into improvement of memristive devices close to a real service condition.

Hydrothermal synthesis and memristive switching behaviors of single-crystalline anatase TiO2 nanowire arrays

A facile one-step hydrothermal method has been reported to prepare the single-crystalline anatase TiO2 nanowire arrays with (101) preferentially oriented on the FTO substrate. The as-prepared Au/TiO2 NWAs/FTO based device exhibits the nonvolatile bipolar memristive switching behaviors with a high HRS/LRS resistance ratio of about three orders of magnitude. The memristive switching behaviors of the device have been elucidated by the Ohmic conduction mechanism and the trap-controlled space charge limited current conduction mechanism. Furthermore, the Schottky barriers modulated by the oxygen vacancies at the Au/TiO2 interface have been suggested to dominate the bipolar memristive switching behaviors of the device. This work demonstrates that the Au/TiO2 NWAs/FTO based device may be a promising candidate for memristor applications.

A facile hydrothermal synthesis and memristive switching performance of rutile TiO2 nanowire arrays

A facile one-step hydrothermal method has been reported to prepare the single crystalline rutile TiO2 nanowire arrays with (101) preferred orientation on the FTO substrate at a low temperature of 120 °C for 4 h. The as-prepared Au/TiO2 NWAs/FTO based device indicates a nonvolatile bipolar memristive switching behavior. The current ratio between low-resistance state and high-resistance state exceeds two orders of magnitude at −0.5 V. The memristive switching behaviors of the device have been elucidated by the Ohmic conduction mechanism and the trap-controlled space charge limited current conduction mechanism. Furthermore, the Schottky barriers modulated by the oxygen vacancies at the Au/TiO2 interface have been suggested to dominate the bias voltages-controlled bipolar memristive switching behaviors of the device. This work indicates that the Au/TiO2 NWAs/FTO based device may be a promising candidate for the memristor applications.

Memristive Switching in Bi(1-x)Sb(x) Nanowires.

We investigated the memristive switching behavior in bismuth-antimony alloy (Bi(1-x)Sb(x)) single nanowire devices at 0.1 ≤ x ≤ 0.42. At 0.15 ≤ x ≤ 0.42, most Bi(1-x)Sb(x) single nanowire devices exhibited bipolar resistive switching (RS) behavior with on/off ratios of approximately 10(4) and narrow variations in switching parameters. Moreover, the resistance values in the low-resistance state (LRS) were insensitive to x. On the other hand, at 0.1 ≤ x ≤ 0.15, some Bi(1-x)Sb(x) single nanowire devices showed complementary RS-like behavior, which was ascribed to asymmetric contact properties. Transmission electron microscopy and elemental mapping images of Bi, Sb, and O obtained from the cross sections of the Bi(1-x)Sb(x) single nanowire devices, which were cut before and after RS, revealed that the mobile species was Sb ions, and the migration of the Sb ions to the nanowire surface brought the switch to LRS. In addition, we demonstrated that two types of synaptic plasticity, namely, short-term plasticity and long-term potentiation, could be implemented in Bi(1-x)Sb(x) nanowires by applying a sequence of voltage pulses with different repetition intervals.

Polymer Side Chain Modification Alters Phase Separation in Ferroelectric-Semiconductor Polymer Blends for Organic Memory.

Side chain modification of a semiconducting polythiophene changes the resulting phase separation length scales when blended with a ferroelectric polymer for use in organic ferroelectric resistive switches. The domain size of the semiconducting portion of blends of poly[3-(ethyl- 5-pentanoate)thiophene-2,5-diyl] (P3EPT) and poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) in thin film blends are smaller than previously reported and easily controllable in size through simple tuning of the weight fraction of the semiconducting polymer. Furthermore, P3EPT has a relatively high degree of crystallinity and bimodal crystallite orientations, as probed by wide-angle X-ray scattering. Resistive switches fabricated from blends of P3EPT and PVDF-TrFE show memristive switching behavior over a wide range of polythiophene content and good ON/OFF ratios.

Gradual electroforming and memristive switching in Pt/CuOx/Si/Pt systems

We report a memristive switching effect in Pt/CuOx/Si/Pt devices prepared by the rf sputtering technique at room temperature. Differently from other Cu-based metal filament switching systems, a gradual electroforming process, marked by a gradual increase of the device resistance and a gradual decrease of the device capacitance, was observed in the current–voltage and capacitance characteristics. After the gradual electroforming, the devices show a uniform memristive switching behavior. By Auger electron spectroscopy analysis, a model based on the thickness change of the SiOx layer at the CuOx/Si interface and Cu ion migration is proposed for the gradual electroforming and uniform memristive switching, respectively. This work should be meaningful for the preparation of forming-free and homogeneous memristive devices.

ZrO2 flexible printed resistive (memristive) switch through electrohydrodynamic printing process

Electrohydrodynamic (EHD) printing technique has been deployed to fabricate flexible printed resistive (memristive) switch in a metal–insulator–metal sandwich structure of Ag/ZrO2/Ag on a polyimide substrate under normal room conditions. The top and bottom electrodes were deposited through the jetting of EHD printing and the active layer of ZrO2 between two electrodes was deposited through the atomization of EHD printing process. The achieved dimensions of the printed device were around 100μm×100μm with the thickness of the bottom electrode, switching layer and top electrode were around 230nm, 680nm and 420nm respectively. The fabricated device showed stable bipolar memristive switching behavior around ±3V. The reversible resistive switching behavior was measured with the high OFF/ON ratio of 100:1. The device kept on exhibiting memristive characteristics after being physically flexed over 500 times that shows its viability for flexible electronics applications.

Memristive switching behavior in Pr0.7Ca0.3MnO3 by incorporating an oxygen‐deficient layer

AbstractWe propose a homogeneous nanoscaled (∅︁ 250 nm) bilayered Pr0.7Ca0.3MnO3 (PCMO)‐based memory device that exhibits low power and good memristive switching behavior. Accurate control of the oxygen‐deficient (PCMO3–x) layer thickness promotes oxygen migration between PCMO3–x and stoichiometric PCMO (PCMO3). The bilayered PCMO structure was confirmed by X‐ray photoelectron spectroscopy analysis. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)