Origin Of Resistive Switching Research Articles

Electrochemical Metallization Memristive Devices with Al Active Electrode Using Engineered Mixed Hexagonal/Orthorhombic Polycrystalline YMnO3

We report electrochemical metallization (ECM) resistive switching in polycrystalline YMnO3 memristive devices using Al as an active electrode. Al/YMnO3/Pt devices exhibit bipolar resistive switching with a high ROFF/RON ratio of 104, low operational voltages of VSet ≈ 1.7 V and VReset ≈ −0.36 V and good retention properties. The resistive switching is intimately linked to the coexistence of the orthorhombic and hexagonal YMnO3 phases. The characterization of these two nanocrystalline phases is realized not only by X‐ray diffraction – which is shown to be unable to reveal the presence of the orthorhombic phase – but also by a set of correlative microscopy and spectroscopy methods (scanning electron microscopy, optical microscopy, Raman spectroscopy and conductive atomic force microscopy). The origin of resistive switching is ascribed to an Al filament‐based electrochemical metallization mechanism that likely occurs along an oxygen‐deficient grain boundary between the hexagonal and orthorhombic nanocrystalline YMnO3 phases. The unique microstructure provided by the mixed polycrystalline phase films allows to use Al as an active electrode in YMnO3‐based ECM cells, and gives perspective for further miniaturization of the devices.

Origin of Resistance Switching and Regulation of the Resistance Stability by the Interface State Density on the Pt/Nb:SrTiO3 Interface

The surface defect and carrier concentrations of Nb‐doped SrTiO3 (NSTO) single crystals play an important role in its resistance switching (RS) properties. Herein, the RS of both 0.05 and 0.7 wt% Nb‐doped NSTO single crystals are studied. The hole defects on NSTO, which are characterized by electron paramagnetic resonance, increase with the enhanced Nb‐doping level. The hole defects with positive charges directly affect the RS characters of the Pt/NSTO junction by electron trapping/detrapping. The stability and discrimination of the resistance states are correlated with the interface state density and carrier concentration, which is controlled by the Nb‐doping level. The fundamental physical processes are proposed according to the experimental results.

On the resistive switching mechanism of parylene-based memristive devices

Abstract Parylene is a widely used polymer possessing such advantages as low cost and safety for the human body. Recently, several studies have been conducted showing that parylene can be used as a dielectric layer of memristors — new circuit design elements that are promising for the implementation of hardware neural networks. However, the mechanism of resistive switching of parylene-based memristors remains unclear. In this paper, we report the result of a comprehensive study of this mechanism for Metal/Parylene/ITO sandwich memristive devices. The obtained results clearly show that the origin of resistive switching in the devices is the formation of conductive metal bridges (filaments) from the top electrode (Cu, Ag or Al) to the bottom one (ITO). And furthermore, conductance quantization effect with both integer and half-integer multiples of the quantum of conductance G0 = 2e2/h has been observed in the samples, which also confirms the chosen switching model, and can be useful in the development of multilevel data memory cells.

Resistive switching and photovoltaic effects in ferroelectric BaTiO3-based capacitors with Ti and Pt top electrodes

We have comparatively studied the dielectric, ferroelectric, conduction, and photovoltaic properties of Ti/BaTiO3 (BTO)/SrRuO3 (SRO) and Pt/BTO/SRO capacitors. The resistive switching (RS) is observed in the Pt/BTO/SRO capacitor while it is absent in the Ti/BTO/SRO capacitor, which may be attributed to the interfacial layer existing between Pt and BTO and the Ti/BTO Ohmic interface, respectively. Further analyses on the conduction mechanisms suggest that the RS may be caused by the opening/closing of conduction paths in the Pt/BTO interfacial layer, whereas the polarization is ruled out as the origin of RS because of the inconsistency between the RS switching voltages and coercive voltages. On the other hand, it is observed that the photovoltaic effects (PVEs) in both Ti/BTO/SRO and Pt/BTO/SRO capacitors are electrically unswitchable and the open-circuit voltages of the two capacitors are similar in magnitude, implying that the PVE is driven by an internal bias field rather than the polarization-induced field. The existence of such an internal bias field is indicated by the self-polarization and imprint phenomena. Our study demonstrates that the interfacial layer and the internal bias field can be the major causes for the RS and PVE in certain ferroelectric capacitors, respectively, whereas the polarization may not necessarily play a role.

Design of Electrodeposited Bilayer Structures for Reliable Resistive Switching with Self-Compliance.

Programmable memory characteristics of electrodeposited CuOx-based resistive random access memory (ReRAM) can be significantly improved by adopting a bilayer structure with a built-in current limiter. To control the on-current and enhance the device uniformity, the bilayer structure of Pt/CuOx (switching layer)/CuOx (current limiter)/Pt is proposed. This structure is synthesized by controlling solution pH during electrochemical deposition (ECD). The bilayer structure of Pt/CuOx (synthesized at pH 9)/CuOx (synthesized at pH 11.5)/Pt exhibits reliable and uniform self-compliant resistive switching behavior. The origin of resistive switching is attributed to formation and rupture of conductive filaments in the CuOx (pH 9) layer. However, the CuOx (pH 11.5) layer acts as the resistor without resistive switching to control the overall resistance in ReRAM. Reversible "on" and "off" switching occurs with a switching time of 100 ns. Devices based on the bilayer structure showed long data retention and good endurance. This simple use of ECD to improve the memory characteristics of electrodeposited ReRAM offers the opportunity to realize reliable and self-compliant memory devices with low-cost solution processes.

Physical Mechanism and Performance Factors of Metal Oxide Based Resistive Switching Memory: A Review

This review summarizes the mechanism and performance of metal oxide based resistive switching memory. The origin of resistive switching (RS) behavior can be roughly classified into the conducting filament type and the interface type. Here, we adopt the filament type to study the metal oxide based resistive switching memory, which considers the migration of metallic cations and oxygen vacancies, as well as discuss two main mechanisms including the electrochemical metallization effect (ECM) and valence change memory effect (VCM). At the light of the influence of the electrode materials and switching layers on the RS characteristics, an overview has also been given on the performance parameters including the uniformity, endurance, the retention, and the multi-layer storage. Especially, we mentioned ITO (indium tin oxide) electrode and discussed the novel RS characteristics related with ITO. Finally, the challenges resistive random access memory (RRAM) device is facing, as well as the future development trend, are expressed.

Resistive switching and its suppression in Pt/Nb:SrTiO3 junctions.

Oxide-based resistive switching devices are promising candidates for new memory and computing technologies. Poor understanding of the defect-based mechanisms that give rise to resistive switching is a major impediment for engineering reliable and reproducible devices. Here we identify an unintentional interface layer as the origin of resistive switching in Pt/Nb:SrTiO3 junctions. We clarify the microscopic mechanisms by which the interface layer controls the resistive switching. We show that appropriate interface processing can eliminate this contribution. These findings are an important step towards engineering more reliable resistive switching devices.

Unravelling the Nature of Unipolar Resistance Switching in Organic Devices by Utilizing the Photovoltaic Effect

The origin of resistive switching in organic devices is studied by photovoltaic methods and impedance spectroscopy. The results show that the most commonly proposed charging/discharging mechanisms can be excluded as working mechanism. There is solid evidence that resistive switching is due to the formation/rupture of filaments. Further, it is shown that this is a universal property of metal/organic/metal thin-film devices.

High-Performance Nanocomposite Based Memristor with Controlled Quantum Dots as Charge Traps

We report a novel approach to improve the resistive switching performance of semiconductor nanorod (NR) arrays, by introducing ceria (CeO2) quantum dots (QDs) as surface charge trappers. The vertically aligned zinc oxide (ZnO) (NR) arrays were grown on transparent conductive glass by electrochemical deposition while CeO2 QDs were prepared by a solvothermal method. Subsequently, the as-prepared CeO2 QDs were embedded into a ZnO NR array by dip coating to obtain a CeO2-ZnO nanocomposite. Interestingly, such a device exhibits excellent resistive switching properties with much higher ON/OFF ratios, better uniformity, and stability over the pure ZnO and CeO2 nanostructures. The origin of resistive switching was studied and the role of heterointerface was discussed.

Analysis of interface switching for Nb doped SrTiO 3 single crystal device using complex impedance spectroscopy

To analyze the switching mechanism of Nb doped SrTiO 3 (Nb:STO) single crystal in a high resistive state (HRS) and low resistive state (LRS), we performed a complex impedance spectroscopy in the frequency domain. We demonstrated the domination of the oxygen vacancies to the resistive switching. Based on the impedance spectroscopy in the HRS and LRS, we concluded that the origin of resistive switching is due to the combination of Schottky junction and a generation of conduction electron from oxygen vacancies. The calculation of activation energies in each resistance state has been performed comparatively, which proposed that a first ionization of oxygen vacancies is responsible for the switching.