Bipolar Resistive Switching Effect Research Articles

Preparation and patterning of HfO2 film via sol–gel method and resistive switching effect of Pt/HfO2/LaNiO3

Sol–gel method is a low-cost material preparation method; however, it is difficult to obtain a stable sol containing easily hydrolyzable metal ions via this method. In this study, a stable hafnium(IV) oxide (HfO2) sol was prepared by adding benzoyl acetone (BzAcH) modifier. Infrared absorption spectroscopy results showed that the BzAcH additive chelated with the Hf4+ ions in the sol, thus improving the hydrolysis resistance of the HfO2 sol, which in turn improved its stability. It was also found that the BzAcH-modified HfO2 gel film exhibited ultraviolet (UV) photosensitivity. After UV exposure, the film did not dissolve easily in organic solvents. Based on these properties, the micro processing of the HfO2 film was preliminarily explored, and HfO2 microstructures were successfully obtained. Additionally, the relative permittivity (εr) of HfO2 exhibited minimum (∼10.9) and maximum (∼20.6) values at heat-treatment (HT) temperatures of 350 and 450 °C, respectively. With the continuous increase in the HT temperature, εr first decreased and then increased slightly. Moreover, the current–voltage curves showed that the Pt/HfO2/LaNiO3 (LNO) structure exhibited a pronounced bipolar resistive switching (RS) effect, which was attributed to the fact that LNO could be used as an electrode and an oxygen vacancy (OV2+) storage layer for RS materials. Notably, the oxygen ions in HfO2 with a low degree of crystallinity are more likely to migrate within its body (which makes it easier to form OV2+s), therefore, the “Set” voltage of low-crystallinity HfO2 films is lower than that of high-crystallinity HfO2 films. The RS mechanism can be explained by the OV2+ conductive filament model. These results are of great practical significance for the low-cost preparation of HfO2 and the application of LNO as an oxide electrode.

Multi-level optical memory with logical operation modulated by surface barrier in a single CH3NH3PbI3 perovskite micro/nanowire device

CH3NH3PbI3 is a potential candidate for optical information storage because of its excellent photoelectric response and hysteresis effect. However, the interface mechanism of the CH3NH3PbI3-based memory is still controversial, and the precise control of the resistive switching effect requires an effective method. Here, single CH3NH3PbI3 micro/nanowire devices with symmetric Ag electrodes were constructed. The role of the reversible redox reaction on the Ag electrode to modulate the interfacial barrier has been proposed, and the hysteresis behavior of the device can be precisely controlled by adjusting the illumination intensity and bias polarity. For example, when strong light and high voltage are applied at the same time, the device exhibits a symmetrical negative differential resistance effect; after being subjected to strong light and high voltage, the device exhibits a bipolar resistive switching effect, and the polarity of the large voltage determines the I-V curve wrapping way. On this basis, the device obtains multi-level optical storage and logic operation functions. This work provides a new way to understand the synergistic memory effect of light and bias on halide perovskite, which is expected to be further applied in the integrated field of optical nonvolatile memory and logical.

Nonvolatile resistive switching in lead-free La2CoMnO6-based memory device

Dense and flat La2CoMnO6 films as the resistive switching functional layer were deposited on n-type Si substrates by sol–gel method. Excellent bipolar resistive switching performance was observed in the Au/La2CoMnO6/Si device for the first time. The high and low resistance states with a ratio of ∼105 could be maintained for more than 1.4 × 104 s and 750 cycles without significant degradation at room temperature. The bipolar resistive switching effect could be sustained within a wide temperature range of 220 K∼300 K. Electrical conduction analysis indicated that the resistive switching behavior in La2CoMnO6 films was primarily controlled by space-charge-limited current mechanism which originated from the change of oxygen vacancies. Density functional theory calculations indicated that the conductive ability of La2CoMnO6 films was promoted with increasing concentration of oxygen vacancies. Moreover, it is found that the modulation of the barrier located at the Au/La2CoMnO6 interface was responsible for the resistive switching under applied bias voltages.

Dielectric and bipolar resistive switching properties of Ag doped As–S–Se chalcogenide for non-volatile memory applications

In this study, dielectric and bipolar resistive switching properties of the chalcogenide from the Ag–As40S30Se30 system were investigated for potential application in non-volatile memory devices. Preparation of the glasses was done with the use of melt-quenching technique. Current–voltage (I–V) characteristics were determined at different temperatures, and stability of the Ag/chalcogenide sample/Ag structure through constant value of memory window was noticed. Namely, it was observed that a bipolar resistive switching effect is present in the prepared samples with noticeable transitions between high-resistance and low-resistance states when the voltage polarity was changed. Temperature dependent I–V measurements indicated that resistive switching voltage decreases as temperature increases suggesting thermally activated motion of charge carriers. The conduction model fitting results suggested that the Ohmic and space-charge limited current conduction are responsible for resistive switch. Based on the analysis of the obtained results, resistive switching mechanism was explained by using filamentary conduction. In addition, study of dielectrical properties indicated presence of space charge polarization. The presented results show that the synthesized material has properties that suggest them for potential application in non-volatile memory devices.

Polarized neutron reflectometry study on the modulation of resistance and magnetism in resistive switching cobalt ferrite thin films

In this work, the resistive switching and electrical-control of magnetization in Pt/CoFe2O4/Nb:SrTiO3 heterostructures have been investigated. The films exhibit a classic bipolar resistive switching effect with a maximum switch ratio of about 5 × 103 and good anti-fatigue performance. Associated with resistive switching, the saturated magnetization of the thin film at high resistance state is found to be larger than that at low resistance state. Meanwhile, polarized neutron reflectivity of the thin film under different resistance states was in situ measured. The results reveal that the interfacial migration of oxygen vacancies driven by an applied electric field plays an important role in the modulation of resistive and magnetism of CoFe2O4 resistive switching devices.

Self-rectifying effect in Au/Al2O3/Si resistive memory structure

To solve the crosstalk problem when the integration density of resistive random access memory (RRAM) devices increase, RRAM with self-rectifying function is required. Herein, the Au/10 nm Al2O3/heavily doped p-type Si (p++-Si) structure was fabricated, and bipolar resistive switching and self-rectifying effect were investigated. A rectification of 6.5 × 103 under ±5 V at low-resistive state (LRS) was observed. The rectifying effect is explained by the energy band diagrams of the structure and electrical conduction mechanism at LRS under negative bias is fitted by space charge limited conduction (SCLC) model. Finally, the endurance and retention properties of the structure were tested. This work would provide insights for further research on the RRAM device with self-rectifying effect, which can alleviate the crosstalk effect without additional switching elements in integrated circuit.

Unraveling the Effect of the Water Content in the Electrolyte on the Resistive Switching Properties of Self-Assembled One-Dimensional Anodized TiO2 Nanotubes.

The applied potential, time, and water content are crucial factors in the electrochemical anodization process because the growth of one-dimensional nanotubes can be accelerated by enhancing the corrosive effect. We investigated the effect of the water content on the resistive switching (RS) properties of Ti foils by anodizing the foils and varying the water content in an electrolyte (1-10 vol %). By increasing the water content, we facilitated a slow transition from nanopores to nanotubes and realized an increase in the tube wall diameter and tube length. All of the fabricated memristive devices exhibited a reliable and reproducible bipolar resistive switching effect. The optimized device exhibited bipolar RS properties with good dc endurance (104 cycles) and data retention capability (105 s). Our results suggest that as the water content increases to 5 vol %, the RS process improves; further increases in the water content impair the RS process.

Bipolar interface-type resistive switching effect in the MoS2–xOx film

Bipolar interface-type resistive switching effect in the MoS2–xOx film

Optical erasable bipolar resistive switching on TiO2 film in nanoscale

Controlling the resistive switching parameters by using external fields is of great importance in the application of the resistive memory devices. In this work, we investigate the effect of light illumination and oxygen atmosphere on the resistive switching of the anatase phase polycrystalline TiO2 thin film using the in-situ conductive atomic force microscopy and Kelvin probe force microscopy. A forming free bipolar resistive switching effect with ON/OFF ratio over 104 was achieved in nanoscale uniformly on the film. The conduction characteristics can be changed from the non-rectifying behavior in vacuum to the Schottky rectifying behavior in oxygen gas with nearly the same ON/OFF ratio. The reversible surface potential shift accompanied by the resistance switching was also observed. Furthermore, the resistance states and the surface potential contrast can be erased by 395 nm near-UV illumination, demonstrating a good optical erasing performance of the device. Combining the surface potential shift and the response to the illumination and oxygen gas, a charge trapping/detrapping mechanism was confirmed to account for the observed switching behavior. These results provide a new way to fabricate the controllable and optical erasable resistive switching devices in nanoscale.

Interfacial resistive switching of Ruddlesden–Popper phase strontium titanate thin film by charge-modulated Schottky barrier

Ruddlesden–Popper (RP) phase Sr2TiO4 thin film is deposited successfully on FTO/glass substrate by spin coating. X-ray diffraction (XRD) pattern shows high-intensity (00 l) (l = 2, 4, and 6) peaks. The device shows bipolar resistive switching (RS) effect. Analysis on current–voltage (I-V) characteristic shows that conduction mechanism is dominated by Schottky emission in both low resistive state (LRS) and high resistive state (HRS). A variation (~0.12 eV) in Schottky barrier height (SBH) is observed between HRS and LRS. Thus, RS at electrode-Sr2TiO4 interface is the main mechanism. In general, variation of SBH is induced by accumulation of interfacial charges. Polarization-voltage (P-V) measurement shows hysteresis loop, which indicates the accumulation of interfacial charges. Formation and migration of charged oxygen vacancies and ions is proposed to be a possible mechanism of interfacial charges accumulation. This study paves the avenue for exploring RS application based on RP phase Sr2TiO4 perovskite oxide.

Forming-free resistive switching in ferroelectric Bi 0.97 Y 0.03 Fe 0.95 Sc 0.05 O 3 film for RRAM application

Electromechanical and resistive switching properties were investigated in ferroelectric rhombohedral Bi 0.97 Y 0.03 Fe 0.95 Sc 0.05 O 3 (BYFSO) film, grown on fluorine-doped tin oxide coated glass substrate. Piezoforce microscopy images of the BYFSO film after the electrical writing indicates the ferroelectric domains were switched completely towards the upward and downward direction at ± 8 V DC bias voltage, which is analogous to the ferroelectric hysteresis curve. The resistive switching effect was investigated on the Ag/BYFSO/FTO RRAM device configuration through conventional I − V characteristics. The charge transport process in Ag/BYFSO/FTO resistive device is transformed from Ohmic to space charge limited current conduction mechanism. The endurance characteristics ensure a stable bipolar resistive switching effect with a large memory window of OFF/ON ratio about ∼100 for 50 repeatable testing cycles. From the impedance spectroscopy analysis, it is observed that the bulk resistance plays a significant role during the SET-RESET process, by large degradation of resistance from megaohm (high resistance state) to kiloohm (low resistance state). The oxygen vacancy induced conductive filaments are responsible for achieving the various resistive states in the device.

Electric control of exchange bias in Co/FeOx bilayer by resistive switching

Two types of electric control of exchange bias (EB) by resistive switching (RS), i.e. conductive-filament-RS (type I) and interface-barrier-RS (type II) were observed in the Si/SiO2Ti/Pt/FeOx/Co/ITO multilayer devices, which were fabricated by magnetron sputtering. It is difficult for the type I device to control EB, which may be due to that the quantity of conductive filaments is not enough to modify the antiferromagnetic structure of FeOx near the Co/FeOx interface. However, the electric control of EB can be accomplished in the type II device. Compared with low-resistance-state (LRS), the exchange bias field (HE) increases a little but the coercivity (HC) increases significantly at high-resistance-state (HRS). We consider that the migration of the oxygen vacancies under different voltages is able to mediate the interfacial barrier height, leading to the bipolar RS effect and the change of EB as well. This provides a way for designing new types of spintronic devices based on electric control.

Organic resistive switching device based on cellulose-gelatine microcomposite fibers

The present work demonstrates the non-volatile resistive switching behavior of cellulose-gelatine microcomposite fibers (CGMFs). The CGMFs were synthesized using the electrospinning technique and used as a switching layer for a resistive memory device. The morphological study reveals that the switching layer was composed of good quality of microcomposite fibers and possesses cross-link like morphology. The functional groups present in the switching layer were confirmed by Fourier-transform infrared spectroscopy technique. The CGMFs based device shows the bipolar resistive switching effect and requires low SET (+ 1.33 V) and RESET (− 1.42 V) voltages for the operation. The charge-magnetic flux relation of the device was calculated and memristive device like properties were observed from the results. The charge driving capability of the device was found to be ~ 1.3 × 10−2 C, which is sufficient to get the good resistive switching property. The non-volatile resistive switching behavior of the CGMFs based device suggested that the device has good performance in terms of endurance (500 cycles) and retention (2000 s). The uniformity and reliability of the device were confirmed by statistical calculations (standard deviation and coefficient of variation). The conduction model fitting results suggested that the space charge limited current (SCLC) and Ohmic conduction mechanisms were responsible for device operation during the high resistance state (HRS) and low resistance state (LRS), respectively. A possible resistive switching mechanism is presented by considering the formation and rupture of Ag conductive filament under the influence of external voltage.

Bipolar resistive switching, synaptic plasticity and non-volatile memory effects in the solution-processed zinc oxide thin film

The memristive devices are getting a lot of interest in recent years due to its applications in the field of resistive memory and brain-inspired computing. In the present work, we have developed a ZnO memristive device using the reflux method. We have demonstrated non-volatile memory properties and mimicked the basic synaptic properties of using Al/ZnO/FTO thin film device. The structural, morphological and compositional studies of ZnO thin film were carried out by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The co-existence of analog and digital resistive switching in a ZnO memristive device was achieved by properly tuning the external electrical stimulus. The developed ZnO memristive device mimics the basic synaptic properties such as potentiation-depression, symmetric Hebbian and antisymmetric Hebbian learning rules at a lower voltage bias (±1 V to ± 3 V). Whereas, non-volatile memory properties (endurance and retention) were achieved at a higher voltage bias (±4 V to ± 6 V). The Al/ZnO/FTO thin film memory device shows good resistive switching memory properties such as 104 endurance cycles and 104 s retention period with good uniformity during the cycle to cycle operation. The detailed analysis of I–V results suggested that the Schottky conduction model is responsible for the analog mode of operation, whereas, space charge limited current governs the device dynamics during the digital mode of operation. A possible resistive switching model is also presented.

Forming-free bipolar resistive switching and quantum conductance in NiO/FTO structures

Forming-free bipolar resistive switching and quantum conductance effects are reported for Au/NiO/FTO structures. The devices show multistep conductance changes during the RESET process for temperatures in the range from 295 to 373 K. Statistical histograms based on 650 switching cycles indicate that the conductivity changes are well represented by integer or half integer multiples of the quantum conductance G0. Temperature dependent I–V measurements below the switching voltages can be described using a Poole–Frenkel model. The mechanism of forming-free bipolar switching and the quantum conductance effect in the Au/NiO/FTO structure is interpreted by multiple quasi-filaments existing in as-grown NiO films and the numbers for the multiple conducting filaments decrease gradually in RESET processes when they rupture gradually.

Resistive Switching Effect with ON/OFF Current Relation up to 109 in 2D Printed Composite Films of Fluorinated Graphene with V2O5 Nanoparticles

AbstractComposite films consisting of fluorinated graphene flakes with vanadium oxide (V2O5) nanoparticles exhibit a stable bipolar resistive switching effect that depends on the size of the composite particles, on the proportion between the film components, on the heat‐treatment conditions of the films (or on the hydration degree of V2O5 nanoparticles), and on the area of the structures. The ON/OFF current ratio of printed crossbar structures reaches 106–109 for films 20–50 nm thick, with the switching voltage varying in the range from 1.5 to 3.7 V, 30 ns time for structure switching, and endurance characteristics up to 1.3 × 103 switching cycles without any changes in ON/OFF current ratio. A mechanism to describe the resistive switching effect implying the formation of sign‐alternating electric fields in a multibarrier structure is proposed. The investigated structures are of interest for the fabrication of nonvolatile memory cells, including memory cells for flexible and printed electronics.

Bipolar resistive switching effect and mechanism of solution-processed orthorhombic Bi2SiO5 thin films

Orthorhombic Bi2SiO5 thin films with dense surface were synthesized by using a chemical solution deposition method. The crystallized films were first utilized to implement resistive memory cells with Pt/Bi2SiO5/Pt sandwich architecture. It exhibited outstanding switching parameters including concentrated distributions of low and high resistance states, uniform switching voltages, cycling endurance, and long retention. Furthermore, the model of formation and rupture of conductive filaments consisted of oxygen vacancies was used to well explain resistive switching behavior. The results revealed that the solution-processed Bi2SiO5 thin film devices have great potential for forefront application in nonvolatile memory.

Resistive switching effect enhanced by light irradiation in C/BaTiO3/C memory structure

The Ta/[C/BaTiO3/C]/Si device was obtained. The resistive switching (RS) behaviors of the Ta/[C/BaTiO3/C]/Si device are studied in the dark and under white-light illumination with various power densities. The results show that the device displays bipolar RS effect, which can be modulated by the white light. And the RS memory device shows biggish resistance ratio, which is more than 105 under white-light irradiation with a power density of 40[Formula: see text]mW/cm2, and the ratio can stabilize at nearly 71 cycles. This work is helpful for the optical control non-volatile memory.

Back-to-back Interface diodes induced symmetrical negative differential resistance and reversible bipolar resistive switching in β-CuSCN trigonal pyramid micro/nanoarray

As a superior p-type wide bandgap semiconductor, β-CuSCN has a huge potential in optoelectronic device application, and however its conduction could intensively be affected by externally applied bias. Here, we demonstrate electrodeposited individual β-CuSCN trigonal micro/nanopyramids and their array films can show Cu+ trap-controlled bias dependence of electron transport. Before being subjected to a large reverse bias or a unidirectional bias, their cyclic IV curves are coincident resulted from bulk-trap related carrier hopping. At relatively large bidirectional operation bias, they can symmetrically present two large hysteresis loops with negative differential resistance (NDR), and meanwhile accompany with nonvolatile negative resistive switching (RS) feature. After being applied respectively a relatively large fixed bias in two opposite directions, more importantly, switchable classic asymmetrical bipolar RS can successfully be realized at a relatively low operation bias. The switchable formation of reversion and depletion layer, resulted from the minority carriers (electrons) injection into the traps of surface connected with negative electrode, plays a crucial role. Under relatively large bias, the synergistic effect of two surface trap-related back-to-back connected bipolar RS devices results in symmetrical negative RS with NDR. After being applied a relatively large fixed bias, the bipolar RS effect can be enhanced at the surface connected with negative electrode due to the presence of electron injection induced high and narrow barrier, and conversely it disappears at the surface connected with positive electrode due to hole injection-induced ohmic contact. Then, the devices can be set and reset by the filling and emptying of holes in the thin reversion and depletion layer at low reverse and forward voltages, respectively, showing switchable bipolar RS behavior. Due to superior stability, reversibility, nondestructive readout, and low operation bias as well as remarkable cycle performance, the bias-governed conduction with negative RS and switchable bipolar RS makes it a potential candidate in next-generation erasable nonvolatile RRAM devices.

Bipolar Resistive Switching Effect in BiFeO3/Nb:SrTiO3 Heterostructure by RF Sputtering at Room Temperature

The (001) oriented BiFeO3 thin film was deposited on the Nb: SrTiO3 substrate by radio frequency magnetron sputtering technology, and the bipolar resistive switching effect was observed in the BiFeO3/Nb: SrTiO3 heterostructure. The results showed that the ratio between the high resistance and low resistance was more than two orders at a reading pulse of -0.5 V and it exhibited excellent retention over 3600 s. The current density-voltage characteristic was dominated by the space-charge-limited conduction. The resistive switching effect of the structure was attributed to the trapping/detrapping of the charge carriers.