Complementary Resistive Switching Research Articles

Implication Logic Circuit Based on a Graphene Oxide Complementary Resistive Switching Device

AbstractThe logic circuit is the main component of an integrated circuit chip that dictates the operation and performance of the chip. The logic circuit based on a memristor can improve the integration and operation speed of the existing integrated circuit and reduce the chip size and the number of devices used by a single logic circuit. However, most of the research on logic circuits based on memristors has focused only on simulations, and research on the realization of logic circuits by hardware using actual memristors is limited. In this paper, a memristor based on graphene oxide with stable complementary resistive switching characteristics is fabricated, a logic circuit is built by using this device, and the logic functions of “IMP,” “AND,” and “NOR” are successfully realized. The complementary resistive switching device can alleviate the severe power loss caused by the memory separation of the von Neumann architecture. Moreover, its unique structure enables it to realize material logic independently without the use of multiple memristors and resistors, providing a new scheme for the physical realization of logic circuits. It also opens up a new path for integrated chips to break through von Neumann architecture.

The Resistance Analysis Attack and Security Enhancement of the IMC LUT Based on the Complementary Resistive Switch Cells

The resistive random access memory (RRAM) based in-memory computing (IMC) is an emerging architecture to address the challenge of the “memory wall” problem. The complementary resistive switch (CRS) cell connects two bipolar RRAM elements anti-serially to reduce the sneak current in the crossbar array. The CRS array is a generic computing platform, for the arbitrary logic functions can be implemented in it. The IMC CRS LUT consumes fewer CRS cells than the static CRS LUT. The CRS array has built-in polymorphic characteristics because the correct logic function cannot be distinguished based on the circuit layout. However, the logic state of every CRS cell can be readout after each operation. It helps the attacker to recover the correct function of the IMC CRS LUT. This work discusses the resistance analysis attack of the IMC LUT based on the CRS array. The proposed resistance analysis attack method is able to be applied to different computation styles based on the CRS array, such as the CRS IMPLY, CRS NOR-OR/NAND-AND, and so on. The attacker can recover the logic function of the LUT by tracing the states of CRS cells. Furthermore, an improved IMC CRS LUT method is proposed and discussed to enhance security. The simulation and analysis results show that the improved IMC CRS LUT can resist various attacks, and it maintains the polymorphic characteristics of the IMC CRS LUT. And the N-bit full adder circuit based on the improved IMC CRS NOR-OR LUTs achieves the best performance compared with the previous counterparts.

Understanding the complementary resistive switching in egg albumen-based single sandwich structure with non-inert Al electrode

The concept of complementary resistive switching (CRS) has been proposed as a potential solution for mitigating the unwanted sneak path current intrinsic to large-scale crossbar memory arrays. In this study, CRS devices based on egg albumen are fabricated using non-inert Al layers as the top electrodes (TE). The Al/Albumen/indium tin oxide (ITO) single sandwich structure achieves stable and reproducible CRS behavior without requiring a forming process. The application of a compliance current leads to an evolution from CRS to bipolar resistive switching (BRS). Furthermore, the BRS analog switching feature enables the emulation of synaptic functions, like paired-pulse facilitation (PPF) and paired-pulse depression (PPD). Our systematic and in-depth analyses demonstrate that the CRS is due to the interfacial Schottky barriers originating from the Al electrode oxidation. Consequently, the resistance switching behavior in the albumen-based cells with inert Pt top electrodes can further validate this model. These findings provide significant insight into the role of non-inert electrodes and contribute to a comprehensive understanding of the CRS mechanism, which may facilitate the development of high-performance CRS biodevices.

Complementary bipolar resistive switching behavior in lithium titanate memory device

In this paper, we report the coexistence of usual bipolar and unique complementary bipolar resistive switching behaviors in an Ag/Li x Ti5O12/Pt memory device. The SET and RESET polarities of the complementary bipolar resistive switching mode were found to be opposite to those of the usual bipolar resistive switching mode. The two bipolar switching modes can be freely converted without altering the compliance current. Based on the conducting filament model, the normal bipolar resistive switching mode is explained by an Ag filament and electrochemical metallization mechanism. Whereas, the complementary bipolar resistive switching behavior is ascribed to Li diffusion and phase transition between Li x Ti5O12 and conducting lithium-rich Li x Ti5O12.

Transition between resistive switching modes in asymmetric HfO2-based structures

We claim that the evolution of conductive filaments (CF) in bipolar resistive switching (BRS) and complementary resistive switching (CRS) is similar in HfO2-based structures with one active layer. The difference in the observed I-V characteristics is explained by the presence of a non-Ohmic contact at the interface with the injection electrode, with the higher barrier at the BRS. In order to describe the transition between BRS and CRS in the asymmetric structure, we form Pt/HfO2(2 nm)/HfOXNY (4 nm)/TiN structure. The active layer of the structure and part of the active electrode were formed via plasma-enhanced atomic layer deposition. Top Pt-electrode was formed via sputtering throughout a shadow mask and area of top electrodes was equal to 0.0360 ± 0.0015 mm2. Pulse and DC measurements of I-V characteristics were carried out. A self-compliance RS with a current lower than 10 mA was found. The primary conduction mechanism in the low-resistance state for both RS modes was estimated as space-charge limited current (SCLC). For BRS, the unusual transition from trap-limited conduction to charge-carrier saturation (I ∼ V1.14) is found to be at 0.35 V in positive bias polarity. Charge-carrier saturation was not found at negative bias polarity. We attribute this to the higher injection barrier on the active electrode side (TiN). We attribute the increase in the barrier height to the accumulation of positive vacancies near the electrode interface.

Resistive Switching Characteristic of Cu Electrode-Based RRAM Device

The conductive bridge random access memory (CBRAM) device has been widely studied as a promising candidate for next-generation nonvolatile memory applications, where Cu as an electrode plays an important role in the resistive switching (RS) process. However, most studies only use Cu as one electrode, either the top electrode (TE) or the bottom electrode (BE); it is rarely reported that Cu is used as both TE and BE at the same time. In this study, we fabricated CBRAM devices by using Cu as both the TE and BE, and studied the RS characteristic of these devices. With Al2O3 as the switching layer (5~15 nm), the devices showed good bipolar RS characteristics. The endurance of the device could be as high as 106 cycles and the retention time could be as long as 104 s. The Al2O3 thickness influences the bipolar RS characteristic of the devices including the initial resistance, the forming process, endurance, and retention performance. The Cu electrode-based RRAM devices also present negative bias-suppressed complementary resistive switching (CRS) characteristics, which makes it effective to prevent the sneak path current or crosstalk problem in high-density memory array circuits.

Charge transport and low-frequency conductance noise in metal-nanoparticle embedded one-dimensional conducting polymer nanotubes: multiple resistive switching phenomena

Metal-nanoparticle embedded benzene tetracarboxylic acid-doped polyaniline (MBDP) nanotubes have been investigated by charge transport measurements and low-frequency 1/f conductance noise spectroscopy for resistive switching (RS) applications. To improve the RS properties, MBDP nanotubes are prepared by in-situ reduction of silver ions (Ag+) on the surface of the benzene tetracarboxylic acid-doped polyaniline (BDP) nanotubes with the silver nanoparticles (Ag NPs). The Ag NPs act like conformal active materials inside BDP nanotubes to effectively control the charge transport by modifying electron-phonon and electron-electron interactions. The RS device on the optimized MBDP (in Ag/MBDP/Ag – configuration) shows a considerable OFF/ON ratio with excellent RS characteristics. The transport results and conductance noise spectroscopy indicate that RS phenomena originated from current-driven space charge limited carrier drift and Columb blocked in transport channels. The RS devices exhibit no noticeable change in RS characteristics even after eighteen months of storage in ambient conditions. Furthermore, the MBDP samples significantly reveal two unipolar switching under varying applied currents and can be used to implement diverse functionalities, including symmetric complementary resistive switching (CRS). This work suggests a suitable route for advancing symmetric CRS characteristics for conducting polymer-based RS memory devices.

Investigation of lithium (Li) doping on the resistive switching property of p-Li:NiO/n-β-Ga2O3 thin-film based heterojunction devices

Li-doped NiO/β-Ga2O3 polycrystalline bilayer thin-film pn-heterojunctions with different Li-doping concentrations are grown on Si-substrates using the pulsed laser deposition technique. Resistive switching property of these devices has been investigated in detail. This study shows that the Li-doping concentration in NiO layer significantly influences the performance of these devices. For an optimum Li-doping of 1.5%, a stable memory window of ∼102 with endurance of more than 100 cycles and long retention time can be achieved. The coefficient of variation (Cv) of SET and RESET voltages also found to ∼ 20% and ∼ 40%, respectively, satisfying the acceptability benchmark. A transition from complementary resistive switching (CRS) to bipolar resistive switching (BRS) after multiple sweeping operations has been observed in devices with intermediate Li-doping concentrations. Observation of CRS has been explained in terms of the formation of Li-rich metallic layer at the NiO/Ga2O3 interface as a result of out-diffusion of Li. Redistribution of the Li-ions from the Li-rich interfacial zone to whole of the NiO layer after first few sweeping cycles must be the reason for CRS-to-BRS transition. Results further suggest that return to high resistive state via Poole–Frenkel (PF) pathway during the RESET process might be the key to achieve high performance in p–n junction based resistive switching devices. This study, thus, presents Li-doping as a possible route to modulate the resistive switching property of bilayer Li:NiO/Ga2O3 based memory devices.

Complementary Resistive Switching in ZnO/Al2O3 Bi-Layer Devices

This paper reports the complementary resistive switching (CRS) characteristics exhibited by Au/ZnO/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> /Fluorine doped tin oxide (FTO) bilayer device for the first time, where both ZnO and 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> are active switching layers exhibiting resistive switching properties. The I-V characteristics of the device initially show bipolar resistive switching (BRS) for a few cycles (∼12) before permanently switching to CRS with the extension of SET voltage. The stable CRS state of the device exhibits a high current of ∼500 μA during the ON-state and low current of 3x10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> A during OFF-state at low input voltages (-0.5 V to 0.5V) enables the proposed device suitable to use in crossbar array to mitigate the sneak path current. The device performance to write and read processes is evaluated with pulses of magnitudes ∼|2.5| V and 1.3 V, respectively, and showed a ∼ 60μA difference in read-out current between data bits 0 and 1. Similarly, the device's power consumption is also measured to elucidate that the device is suitable to use as a memory unit with power consumption in the order of microwatts (μW). Further, the possible switching mechanism is demonstrated based on oxygen vacancies migration.

Effect of long chain fatty acids on the memory switching behavior of tetraindolyl derivatives.

Non-volatile memory devices using organic materials have attracted much attention due to their excellent scalability, fast switching speed, low power consumption, low cost etc. Here, we report both volatile as well as non-volatile resistive switching behavior of p-di[3,3'-bis(2-methylindolyl)methane]benzene (Indole2) and its mixture with stearic acid (SA). Previously, we have reported the bipolar resistive switching (BRS) behavior using 1,4-bis(di(1H-indol-3-yl)methyl)benzene (Indole1) molecules under ambient conditions [Langmuir 37 (2021) 4449-4459] and complementary resistive switching (CRS) behavior when the device was exposed to 353 K or higher temperature [Langmuir 38 (2022) 9229-9238]. However, the present study revealed that when the H of -NH group of Indole1 is replaced by -CH3, the resultant Indole2 molecule-based device showed volatile threshold switching behaviour. On the other hand, when Indole2 is mixed with SA at a particular mole fraction, dynamic evolution of an Au/Indole2-SA/ITO device from volatile to non-volatile switching occurred with very good device stability (>285 days), memory window (6.69 × 102), endurance (210 times), data retention (6.8 × 104 s) and device yield of the order of 78.5%. Trap controlled SCLC as well as electric field driven conduction was the key behind the observed switching behaviour of the devices. In the active layer, trap centers due to the SA network may be responsible for non-volatile characteristics of the device. Observed non-volatile switching may be a potential candidate for write once read many (WORM) memory applications in future.

Thermal stable and low current complementary resistive switch with limited Cu source in amorphous carbon

In this Letter, we report a complementary resistive switch (CRS) with good thermal stability and low ON current. The device is constructed with a bilayer structure composed of sputtered amorphous carbon (a-C) and thermal annealed Cu doped a-C (a-C:Cu). The Cu atoms in a-C:Cu can agglomerate to form nanosized active electrodes by thermal annealing. The Cu species can migrate and redistribute to form conductive filaments within the a-C and a-C:Cu layer through an electrochemical redox reaction. The depletion of Cu species in the a-C:Cu or a-C layer produces complementary resistive switching behaviors. Benefiting from the high thermal stability of a-C and a-C:Cu, the device works stable at a high temperature of up to 300 °C with an endurance of 104 switching cycle and narrow cycle-to-cycle distribution of threshold voltages. Furthermore, the effects of the Cu content in the a-C:Cu layer and the thickness ratio of a-C:Cu/a-C on the ON state current were studied. By limiting the content of Cu in the a-C:Cu layer, a low ON state current of 5 μA was obtained, which is among the lowest in the reported CRSs. Furthermore, a “stateful” material implication logic with the “0” and “1” states represented by a distinct combination of the resistance of each layer was implemented. The CRS is a potential and promising device for low power memory/computing applications and harsh electronics.

Influence of non-inert electrode thickness on the performance of complementary resistive switching in AlOxNy-based RRAM

This Letter investigates the effect of non-inert electrode thickness on the performance of complementary resistive switching (CRS). Five devices with different Ta electrode thicknesses (0, 2, 5, 10, and 20-nm) are fabricated. For devices with 2, 5, and 10-nm electrode thicknesses, CRS behavior can be obtained through an evolution process, while devices with 0 and 20-nm Ta electrode thicknesses always maintain stable bipolar resistive switching behavior. By analyzing the evolution process and current conduction mechanisms, the influence of non-inert electrode thickness on the performance of CRS is studied, and different oxidation degrees of a non-inert electrode are used to explain the different resistive switching performance in these devices. Aside from that, the model is verified by applying an asymmetric voltage sweeping method. This paper further clarifies the physical mechanism of CRS behavior in non-inert electrode resistive random access memory and provides a way to optimize the performance of CRS behavior.

Enhancement of resistive switching behavior of organic resistive random access memory devices through UV-Ozone treatment

We fabricated organic resistive random-access memory (RRAM) devices using a low-cost solution-process method. All the processes were performed at temperatures below 135 °C under ambient atmospheric conditions. The RRAM resistive switching layer was formed from a polymer-fullerene bulk heterojunction using poly(3-hexylthiophene-2,5-diyl) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM). The fabricated organic RRAM device exhibited typical nonvolatile bipolar resistive switching behavior with an ON/OFF ratio of ∼40, but it provided a low endurance of 27 cycles. Therefore, for enhanced stability, simple UV–Ozone (UVO) treatment was applied to the P3HT:PCBM organic bulk heterojunction layer. The organic RRAM device with UVO treatment exhibited an enhanced performance with an ON/OFF ratio of ∼400 and an endurance of 47 cycles. In addition, complementary resistive switching behavior was observed. The conduction mechanisms of the organic RRAM device were investigated by fitting the measured I–V data to numerical equations, and Schottky emission and Ohmic conduction were the main conduction mechanisms for the high-resistance and low-resistance states for the RRAM device with or without UVO treatment.

Complementary Resistive Switching Behavior in Tetraindolyl Derivative-Based Memory Devices.

Complementary resistive switching (CRS) devices are more advantageous compared to bipolar resistive switching (BRS) devices for memory applications as they can minimize the sneak path problem observed in the case of BRS having a crossbar array structure. Here, we report the CRS behavior of 1,4-bis(di(1H-indol-3-yl)methyl)benzene (Indole1) molecules. Our earlier study revealed that Au/Indole1/Indium tin oxide (ITO) devices showed BRS under ambient conditions. However, the present investigations revealed that when the device is exposed to 353 K or higher temperatures, dynamic evolution of the Au/Indole1/ITO device from BRS to CRS occurred with a very good memory window (∼103), data retention (5.1 × 103 s), stability (50 days), and device yield (∼ 60%). This work explores the application possibility of indole derivatives toward future ultradense resistive random access memory.

An improved reconfigurable logic in resistive random access memory

Emerging non-volatile devices have shown great potential in computing in-memory (CIM). This work proposes a logic design method based on the complementary resistance switching (CRS) structure, which is connected by two anti-serially memristors. Three logics including AND, OR, and NIMP can be implemented in one step. Moreover, XOR logic can be implemented in two steps. Based on the proposed design, a 1-bit full adder is implemented with the fewer number of memristors and operation steps compared with existing works. The feasibility and correctness of our design are verified by the SPICE simulations with the Voltage Threshold Adaptive Memristor (VTEAM) model. In addition, we evaluate the ISCAS’85 benchmark circuit based on the proposed logic. Compared with existing methods, the performance and area overhead have been improved by the proposed method.

In-Memory Hamming Error-Correcting Code in Memristor Crossbar

This article proposes an in-memory Hamming error-correcting code (ECC) in the memristor crossbar array (CBA). Based on the unique <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}{-}{V}$ </tex-math></inline-formula> characteristic of complementary resistive switching (CRS) memristor, this work discovers that a combination of three memristors behaves as a stateful EXCLUSIVE-OR (XOR) logic device. In addition, a two-step (build-up and fire) current-mode CBA driving scheme is proposed to realize a linear increment of the build-up voltage that is proportional to the number of low-resistance state (LRS) memristors in the array. Combining the proposed XOR logic device and the driving scheme, we realize a complete stateful XOR logic, which enables a fully functional in-memory Hamming ECC, including parity bit generation and storage followed by syndrome vector calculation/readout. The proposed technique is verified by a simulation program with integrated circuit emphasis (SPICE) simulations, with a Verilog-A CRS memristor model and a commercial 45-nm CMOS process design kit (PDK). The verification results prove that the proposed in-memory ECC perfectly detects error regardless of data patterns and error locations with enough margin.

A complementary resistive switching neuron

The complementary resistive switching (CRS) memristor has originally been proposed for use as the storage element or artificial synapse in large-scale crossbar array with the capability of solving the sneak path problem, but its usage has mainly been hampered by the inherent destructiveness of the read operation (switching ‘1’ state to ‘ON’ or ‘0’ state). Taking a different perspective on this ‘undesired’ property, we here report on the inherent behavioral similarity between the CRS memristor and a leaky integrate-and-fire (LIF) neuron which is another basic neural computing element, in addition to synapse. In particular, the mechanism behind the undesired read destructiveness for storage element and artificial synapse can be exploited to naturally realize the LIF and the ensuing spontaneous repolarization processes, followed by a refractory period. By means of this biological similarity, we demonstrate a Pt/Ta2O5−x /TaO y /Ta CRS memristor that can exhibit these neuronal behaviors and perform various fundamental neuronal operations, including additive/subtractive operations and coincidence detection. These results suggest that the CRS neuron, with its bio-interpretability, is a useful addition to the family of memristive neurons.

Low power memristive gas sensor architectures with improved sensing accuracy

Memristive devices, traditionally considered for memory, logic, and neuromorphic systems, are exhibiting many interesting properties for applications in a variety of areas, such as in sensing chemicals. However, any realistic approach based on these devices must take into account their susceptibility to process and parametric variations. When used for sensing purposes this, together with wire resistance, can significantly degrade their sensing accuracy. To this end, we propose novel memristive gas sensor architectures that can significantly reduce these effects in a predictable manner, while improving accuracy and overall power consumption. Additionally, we show that in the absence of gasses this architecture can also be configured to realize multifunction logic operations as well as Complementary Resistive Switch with low hardware overhead, thereby enhancing resource reusability. We also present a method for further improving power consumption and measurability by manipulating a device’s internal barrier. Our results show that the proposed architecture is significantly immune to process and parametric variations compared to a single sensor and almost unaffected by wire resistance, while offering much higher accuracy and much lower power consumption compared to existing techniques.

Dynamic evolution process from bipolar to complementary resistive switching in non-inert electrode RRAM

At present, the physical mechanism of complementary resistive switching (CRS) devices remains controversial. In this Letter, stable CRS can be achieved in Pt/AlOxNy/Ta resistive random access memory (RRAM). A dynamic evolution from bipolar resistive switching to CRS can be evidently observed in non-inert electrodes RRAM. The causes of CRS behavior are analyzed in detail, and these phenomena are attributed to the different oxidation degrees of the top electrode and propose that the transition state can be used as a signal for the emergence of CRS behavior. Moreover, the model is partially supported by measured switching behavior of the Pt/AlOxNy/TaOx device. This research contributes to the understanding of the CRS behavior physical mechanism in non-inert electrodes RRAM devices.

SPICE model for complementary resistive switching devices based on anti-serially connected quasi-static memdiodes

This paper reports the use of the Quasi-static Memdiode Model (QMM) for simulating Complementary Resistive Switching (CRS) devices. CRS arises from the anti-serial connection of two memristors and it is used for generating low and high-resistance regions in the I-V characteristic with the aim of mitigating the sneak-path conduction problem in crossbar arrays. Here, the use of the QMM for CRS in the form of a six terminal subcircuit is explored. While two terminals of the subcircuit correspond to the conventional input and output pins of the CRS structure, the rest provide information about the voltage at the central node, the low-voltage conductance of each device, and the low-voltage conductance of the whole structure. Special attention is paid to the simulation of the so-called table with legs hysteresis loop (resistance at fixed bias vs. write voltage), which is often invoked in connection with devices that exhibit switching activity at the two interfaces of a single dielectric layer. Because of the internal potential drop distribution, the switching process takes place alternately at one side of the structure or the other giving rise to a pseudo-CRS behavior. The flexibility of the proposed approach is demonstrated through a series of fitting exercises that involve experimental data reported in the literature. The model script for the SPICE simulator is also provided.