Reproducible Bipolar Resistive Switching Research Articles

High performance nonvolatile memory devices based on Cu2−xSe nanowires

We report on the rational synthesis of one-dimensional Cu 2−xSe nanowires (NWs) via a solution method. Electrical analysis of Cu 2−xSe NWs based memory device exhibits a stable and reproducible bipolar resistive switching behavior with a low set voltage (0.3–0.6 V), which can enable the device to write and erase data efficiently. Remarkably, the memory device has a record conductance switching ratio of 108, much higher than other devices ever reported. At last, a conducting filaments model is introduced to account for the resistive switching behavior. The totality of this study suggests that the Cu 2−xSe NWs are promising building blocks for fabricating high-performance and low-consumption nonvolatile memory devices.

Highly repeatable multilevel resistive switching characteristics of an Au/TiO2/Ti memory device

Development of a highly repeatable multilevel resistive switching Au/TiO2/Ti memory device is reported in this paper. Undoped rutile TiO2 thin film, having a thickness of 480 nm, was grown on high-purity Ti (99.5%) by in situ thermal oxidation technique at 600 °C. Au metal contact was used as a top electrode. The developed Au/TiO2/Ti memory device was electrically characterized for resistive random access memory applications and found to have extremely repeatable, reproducible and stable bipolar resistive switching characteristics. With very low ‘SET’ and ‘RESET’ voltage requirement, the device offered highly symmetric multilevel high- to low-resistance state transitions. The two pairs of ‘SET’ and ‘RESET’ voltages were ±0.26 V and ±0.64 V. As there is no requirement of electroforming voltages, low electric field operation of the device is ensured, which eventually leads to the avoidance of high field hazards. The effect of operating temperature on the performance of Au/TiO2/Ti memory devices was also investigated in the temperature range of 27–80 °C, and the device offered negligible shift in the characteristics, ensuring high-temperature stability. The multilevel switching phenomenon was explained by appropriate defect models.

Bipolar resistive switching characteristics in CuO/ZnO bilayer structure

Resistive switching characteristics in Cu/ZnO/AZO (Al-doped ZnO) were investigated. Reproducible bipolar resistance switching properties were observed in the single oxide layer (SL)-based device. To improve the switching performance, a CuO–ZnO bilayer (BL) was used to form a Cu/CuO/ZnO/AZO structure. RS characteristics such as retention time, endurance, variations of threshold voltage as well as distribution of resistance were investigated. The results demonstrated that the BL devices exhibit more excellent switching performance than SL devices. The conduction mechanisms of high and low resistance states can be explained by trap-controlled space charge limited current (SCLC) and Ohmic's Law, respectively. The CuO layer is proposed as a “reservoir” of oxygen ions in set process and acting as an oxygen ions “supplier” in reset process, which plays a critical role in recovery/rupture of filament paths and greatly improves the switching characteristics of the device.

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.

Bipolar resistive switching of solution processed TiO2–graphene oxide nanocomposite for nonvolatile memory applications

Abstract In this study, we report the observation of memory effect in TiO2–GO nanocomposite films. Electrical properties of the prepared Al/TiO2–GO composite/ITO devices have shown stable and reproducible bipolar resistive switching behavior. The TiO2–GO composite films were prepared using solution method by spin coating technique. Observed results have shown that the inclusion of GO in the TiO2 matrix have exhibited a significant role in the resistive switching mechanism. The device has exhibited an excellent memory characteristic with low operating voltages, good endurance up to 105 cycles and long retention time more than 5 × 10 3 s .

Electrical Performance and Scalability of Pt Dispersed SiO2Nanometallic Resistance Switch

Highly reproducible bipolar resistance switching was recently demonstrated in a composite material of Pt nanoparticles dispersed in silicon dioxide. Here, we examine the electrical performance and scalability of this system and demonstrate devices with ultrafast (<100 ps) switching, long state retention (no measurable relaxation after 6 months), and high endurance (>3 × 10(7) cycles). A possible switching mechanism based on ion motion in the film is discussed based on these observations.

Poly-NiO/Nb:SrTiO&lt;sub&gt;3&lt;/sub&gt; Based Resistive Switching Device for Nonvolatile Random Access Memory

The bipolar resistive switching characteristic of Ag/poly-NiO/Nb:SrTiO3/In device has been investigated in this letter. The current-voltage characteristics of the device shows reproducible and pronounced bipolar resistive switching after 2V forming process and the resistive switching ratio RHRS/RLRS can reach 104 at the read voltage -0.5V. Multilevel memories can be realized by changing the max reverse voltages and show well retention characteristic even after several sweeping cycles. The results have been discussed in terms of carrier injection process via defects at the interface of the poly-NiO and Nb:SrTiO3.

Bipolar resistive switching in an amorphous zinc tin oxide memristive device

The integration of amorphous zinc tin oxide (ZTO) into crossbar memristor device structures has been investigated where asymmetric devices were fabricated with Al (top) and Pt (bottom) electrodes. The authors found that these devices had reproducible bipolar resistive switching with high switching ratios &amp;gt;104 and long retention times of &amp;gt;104 s. Electrical characterization of the devices suggests that both filamentary and interfacial mechanisms are important for device switching. The authors have used secondary ion mass spectrometry to characterize the devices and found that significant interfacial reactions occur at the Al/ZTO interface.

Bipolar and tri-state unipolar resistive switching behaviors in Ag/ZnFe2O4/Pt memory devices

We report on the co-existence of bipolar and unipolar resistive switching behaviors in Ag/ZnFe2O4/Pt structures of which the ZnFe2O4 layer was fabricated by a chemical solution deposition method. The memory devices show reproducible and stable bipolar resistive switching, tri-state unipolar resistive switching under only applied negative bias voltage, and unipolar resistive switching transited from bipolar resistive switching with different electroforming conditions. Excellent switching cycling in both unipolar resistive switching and bipolar resistive switching is demonstrated. Based on the conducting filament model, electrochemical metallization effect has been proposed to explain the bipolar resistive switching behavior, whereas the unipolar resistive switching behavior is attributed to electrochemical metallization effect and thermochemical effect.

Bipolar Resistive Switching Characteristic of Epitaxial NiO Thin Film on Nb-Doped Substrate

Epitaxial NiO film was grown on 0.7% Nb-doped substrates by pulsed laser deposition. TheI-Vcharacteristics of Ag/NiO/Nb-/In device show reproducible and pronounced bipolar resistive switching without forming process which was induced by the NiO/Nb- junctions, and the resistive switching ratio can reach 103at the read voltage of −0.5 V. Furthermore, the resistance states can be controlled by changing the max forward voltage, reverse voltage, or compliance current, indicating multilevel memories. These results were discussed by considering the role of carrier injection trapped/detrapped at the interfacial depletion region of the heterojunction.

Bipolar resistive switching with self-rectifying effects in Al/ZnO/Si structure

We report the electrical characteristics of room-temperature-fabricated Al/ZnO/Si memory devices. Stable and reproducible clockwise bipolar resistive switching phenomena with self-rectifying effects in the low resistance state were observed in this complementary metal oxide semiconductor compatible memory structure. The current-voltage curve in different temperatures and the corresponding Arrhenius plot confirm the semiconducting conduction behavior of both the high resistance state and the low resistance state. The conduction mechanisms are explained by the Poole-Frenkel emission and space-charge-limited conduction mechanisms for the high resistance state and the low resistance state, respectively. It is proposed that the resistive switching originates from the formation and dissolution of the AlOx barrier layer which are induced by the migration of the oxygen ions.

Bipolar Resistive Switching in Al/HfO2/In0.53Ga0.47As MIS Structures

Reproducible bipolar resistive switching behavior observed in Metal-Insulator-Semiconductor (Al/HfO2/In0.53Ga0.47As) structures is reported. The resistive switching originates from the redox phenomenon at the Al gate electrode which is induced by the migration of the oxygen ions. Low-frequency noise measurement is used to study the current fluctuation mechanisms. Scanning tunneling microscopy results confirm the formation of conducting filaments during the SET process in the devices.

Bipolar Nonlinear $\hbox{Ni/TiO}_{2}\hbox{/}\hbox{Ni}$ Selector for 1S1R Crossbar Array Applications

A bipolar nonlinear selector to suppress the sneak current in the crossbar array has been fabricated using a simple Ni/TiO2/Ni metal-insulator-metal structure. The highly nonlinear current-voltage characteristics are realized by the Schottky emission over the Ni/TiO2 barriers. The series connection with an HfO2-resistive memory device shows reproducible bipolar resistive switching. The maximum array size with at least 10% read margin is projected to exceed megabits. This letter demonstrates the promise of the compact one selector-one resistor (1S1R) cell structure for high-density crossbar array applications.

Resistive switching mechanism of Ag/ZrO2:Cu/Pt memory cell

Resistive switching mechanism of zirconium oxide-based resistive random access memory (RRAM) devices composed of Cu-doped ZrO2 film sandwiched between an oxidizable electrode and an inert electrode was investigated. The Ag/ZrO2:Cu/Pt RRAM devices with crosspoint structure fabricated by e-beam evaporation and e-beam lithography show reproducible bipolar resistive switching. The linear I–V relationship of low resistance state (LRS) and the dependence of LRS resistance (RON) and reset current (Ireset) on the set current compliance (Icomp) indicate that the observed resistive switching characteristics of the Ag/ZrO2:Cu/Pt device should be ascribed to the formation and annihilation of localized conductive filaments (CFs). The physical origin of CF was further analyzed by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). CFs were directly observed by cross-sectional TEM. According to EDS and elemental mapping analysis, the main chemical composition of CF is determined by Ag atoms, coming from the Ag top electrode. On the basis of these experiments, we propose that the set and reset process of the device stem from the electrochemical reactions in the zirconium oxide under different external electrical stimuli.

Bipolar resistive switching in Cu/AlN/Pt nonvolatile memory device

Highly stable and reproducible bipolar resistive switching effects are reported on Cu/AlN/Pt devices. Memory characteristics including large memory window of 103, long retention time of &amp;gt;106 s and good endurance of &amp;gt;103 were demonstrated. It is concluded that the reset current decreases as compliance current decreases, which provides an approach to suppress power consumption. The dominant conduction mechanisms of low resistance state and high resistance state were verified by Ohmic behavior and trap-controlled space charge limited current, respectively. The memory effect is explained by the model concerning redox reaction mediated formation and rupture of the conducting filament in AlN films.

Highly Uniform Bipolar Resistive Switching With $ \hbox{Al}_{2}\hbox{O}_{3}$ Buffer Layer in Robust NbAlO-Based RRAM

The bipolar resistive switching characteristics of atomic-layer-deposited NbAlO-based devices have been investigated for nonvolatile memory applications. With the help of a thin Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> buffer layer, highly uniform and reproducible bipolar resistance switching cycles could be observed. Four typical multilevel operations, with resistances being at 1000, 350, 145, and 75 ¿, respectively, are also successfully demonstrated by varying the current compliance during the set process. The resistance ratios of high-resistance state to low-resistance state are more than 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> within 5000 cycles during the test without any degradation. Moreover, the estimated retention lifetime at room temperature is sufficiently long to fulfill the typical ten-year requirement. Considering its excellent memory switching behavior, a resistance switching device composed of a NbAlO film with a thin Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> buffer layer is a possible candidate to be integrated into future memory processes.

The Resistive Switching Mechanism of Ag/SrTiO[sub 3]/Pt Memory Cells

Reproducible and reliable bipolar resistive switching was obtained from Ag/SrTiO 3 (STO)/Pt memory cells. The current-voltage characteristic of the Ag/STO/Pt cells with a positive voltage applied to the Pt electrode and the results of X-ray photoelectron spectroscopy imply that the electrochemical reaction and the diffusion of Ag + ions play a critical role in the resistive switching effect. The temperature dependence of the on-state resistance, combined with the time dependence of the on- and off-state resistances under a constant voltage, provides further evidence that the resistive switching mechanism should be ascribed to the formation and dissolution of the metallic Ag nanofilaments.

Bipolar resistive switching behavior in Ti/MnO2/Pt structure for nonvolatile memory devices

This study examined the electrical properties of Ti/MnO2/Pt devices with stable and reproducible bipolar resistive switching behavior. The dependency of the memory behavior on the cell area and operating temperature suggest that the conducting mechanism in the low resistance states is due to the locally conducting filaments formed. X-ray photoelectron spectroscopy showed that nonlattice oxygen ions form at the MnO2 surface. The mechanism of resistance switching in the system examined involves the generation and recovery of oxygen vacancies with the nonlattice oxygen ions.

Conductance switching in Ag2S devices fabricated by in situ sulfurization

We report a simple and reproducible method to fabricate switchableAg2S devices.The α-Ag2S thin films are produced by a sulfurization process after silverdeposition on an Si substrate. Structure and composition of theAg2S are characterized using XRD and RBS. Our samples show semiconductor behaviour at lowbias voltages, whereas they exhibit reproducible bipolar resistance switching at higher biasvoltages. The transition between both types of behaviour is observed by hysteresis in theI–V curves, indicatingdecomposition of the Ag2S, increasing the Ag+ ionmobility. The as-fabricated Ag2S samples are a good candidate for future solid state memory devices, as they showreproducible memory resistive properties and they are fabricated by an accessible andreliable method.

Reproducible low-current resistive switching of metal/Pr0.7Ca0.3MnO3/Pt junctions with a point-contact top electrode

Current-voltage （I-V） and the electrical pulse induced resistive switching （EPIR）characteristics of metal/Pr0.7Ca0.3MnO3/Pt sandwich structures, where the metal is a point-contact Pt or W electrode, are investigated by using a home-made conductive AFM. The structures with both Pt and W tips behaves as rather reproducible bipolar resistive switching （RS） with an RS ratio larger than 100. However W/Pr0.7Ca0.3MnO3/Pt structures shows EPIR under a compliance current of 10 nA and reproducible bipolar RS under a compliance current of 100 pA，which is about three orders lower than the published values and shows the potential applications in low power memory device. Further analysis of I-V characteristics at different positions of sample，under different current compliances， with different contact areas of device suggests that an enhanced oxygen vacancy migration due to point contact induced local intense electrical field， gives rise to a stable RS for Pt/Pr0.7Ca0.3MnO3/Pt devices.