Ideal Memristor Research Articles

A new memristor-based fractional-order chaotic system

In this paper, a new four-dimensional incommensurate fractional-order system is proposed by introducing an ideal flux-controlled memristor into a three-dimensional chaotic system, and combining it with fractional-order calculus theory, which is solved by using the Adomian decomposition method (ADM). Through theoretical analysis we found the system has numerous equilibrium points. Compared with the original system, the modified system exhibits richer dynamical behaviors. The main manifestations are: (i) Antimonotonicity varying with the initial value. (ii) Three kinds of transient transition behaviors: transient asymptotically-period (A-period), transient chaos, and tri-state transition (chaos-A-period-chaos). (iii) Initial offset boosting behavior. (iv) Hidden extreme multistability. (v) As the order q changes, the system is capable of generating a variety of asymptotically periodic attractors and chaotic attractors. These behaviors above are analyzed in detail by means of numerical simulations such as phase diagram, bifurcation diagram, Lyapunov exponent spectrum (LEs), time-series diagram, and attraction basin. Finally, the system is implemented with a hardware circuit based on a digital signal processor (DSP), which in turn proved the correctness of the numerical analysis simulations and the physical realizability of the system.

Memristor Circuits for Simulating Neuron Spiking and Burst Phenomena.

Since the introduction of memristors, it has been widely recognized that they can be successfully employed as synapses in neuromorphic circuits. This paper focuses on showing that memristor circuits can be also used for mimicking some features of the dynamics exhibited by neurons in response to an external stimulus. The proposed approach relies on exploiting multistability of memristor circuits, i.e., the coexistence of infinitely many attractors, and employing a suitable pulse-programmed input for switching among the different attractors. Specifically, it is first shown that a circuit composed of a resistor, an inductor, a capacitor and an ideal charge-controlled memristor displays infinitely many stable equilibrium points and limit cycles, each one pertaining to a planar invariant manifold. Moreover, each limit cycle is approximated via a first-order periodic approximation analytically obtained via the Describing Function (DF) method, a well-known technique in the Harmonic Balance (HB) context. Then, it is shown that the memristor charge is capable to mimic some simplified models of the neuron response when an external independent pulse-programmed current source is introduced in the circuit. The memristor charge behavior is generated via the concatenation of convergent and oscillatory behaviors which are obtained by switching between equilibrium points and limit cycles via a properly designed pulse timing of the current source. The design procedure takes also into account some relationships between the pulse features and the circuit parameters which are derived exploiting the analytic approximation of the limit cycles obtained via the DF method.

A Novel Memristor Chaotic System with a Hidden Attractor and Multistability and Its Implementation in a Circuit

By introducing an ideal and active flux-controlled memristor and tangent function into an existing chaotic system, an interesting memristor-based self-replication chaotic system is proposed. The most striking feature is that this system has infinite line equilibria and exhibits the extreme multistability phenomenon of coexisting infinitely many attractors. In this paper, bifurcation diagrams and Lyapunov exponential spectrum are used to analyze in detail the influence of various parameter changes on the dynamic behavior of the system; it shows that the newly proposed chaotic system has the phenomenon of alternating chaos and limit cycle. Especially, transition behavior of the transient period with steady chaos can be also found for some initial conditions. Moreover, a hardware circuit is designed by PSpice and fabricated, and its experimental results effectively verify the truth of extreme multistability.

A Flux Controlled Memristor using 90nm Technology

A flux-controlled memristor using complementary metal–oxide–(CMOS) structure is presented in this study. The proposed circuit provides higher power efficiency, less static power dissipation, lesser area, and can also reduce the power supply by using CMOS 90nm technology. The circuit is implemented based on the use of a second-generation current conveyor circuit (CCII) and operational transconductance amplifier (OTA) with few passive elements. The proposed circuit uses a current-mode approach which improves the high frequency performance. The reduction of a power supply is a crucial aspect to decrease the power consumption in VLSI. An offered emulator in this proposed circuit is made to operate incremental and decremental configurations well up to 26.3 MHZ in cadence virtuoso platform gpdk using 90nm CMOS technology. proposed memristor circuit has very little static power dissipation when operating with ±1V supply. Transient analysis, memductance analysis, and dc analysis simulations are verified practically with the Experimental demonstration by using ideal memristor made up of ICs AD844AN and CA3080, using multisim which exhibits theoretical simulation are verified and discussed.

A Flux Controlled Memristor using 90nm Technology

A flux-controlled memristor using complementary metal–oxide–(CMOS) structure is presented in this study. The proposed circuit provides higher power efficiency, less static power dissipation, lesser area, and can also reduce the power supply by using CMOS 90nm technology. The circuit is implemented based on the use of a second-generation current conveyor circuit (CCII) and operational transconductance amplifier (OTA) with few passive elements. The proposed circuit uses a current-mode approach which improves the highfrequency performance. The reduction of a power supply is a crucial aspect to decrease the power consumption in VLSI. An offered emulator in this proposed circuit is made to operate incremental and decremental configurations well up to 26.3 MHZ in cadence virtuoso platform gpdk using 90nm CMOS technology. proposed memristor circuit has very little static power dissipation when operating with ±1V supply. Transient analysis, memductance analysis, and dc analysis simulations are verified practically with the Experimental demonstration by using ideal memristor made up of ICs AD844AN and CA3080, using multisim which exhibits theoretical simulation are verified and discussed.

A flexible BiFeO3-based ferroelectric tunnel junction memristor for neuromorphic computing

Ferroelectric tunnel junctions (FTJs) as the artificial synaptic devices have been considered promising for constructing brain-inspired neuromorphic computing systems. However, the memristive synapses based on the flexible FTJs have been rarely studied. Here, we report a flexible FTJ memristor grown on a mica substrate, which consists of an ultrathin ferroelectric barrier of BiFeO3, a semiconducting layer of ZnO, and an electrode of SrRuO3. The obtained flexible FTJ memristor exhibits stable voltage-tuned multi-states, and the resistive switchings are robust after 103 bending cycles. The capability of the FTJ as a flexible synaptic device is demonstrated by the functionality of the spike-timing-dependent plasticity with bending, and the accurate conductance manipulation with small nonlinearity (−0.24) and low cycle-to-cycle variation (1.77%) is also realized. Especially, artificial neural network simulations based on experimental device behaviors reveal that the high recognition accuracies up to 92.8% and 86.2% are obtained for handwritten digits and images, respectively, which are close to the performances for ideal memristors. This work highlights the potential applications of FTJ as flexible electronics for data storage and processing.

The impact of memristive coupling initial states on travelling waves in an ensemble of the FitzHugh–Nagumo oscillators

A ring of the FitzHugh–Nagumo (FHN) oscillators coupled via memristive elements is studied. The impact of the memristive element initial states on the travelling wave characteristics is established for the self-oscillatory and excitable dynamics of the individual oscillators. It is shown that the initial state effect is especially evident in the excitable regime. In such a case the initial distribution of the memristive element states affects on the wave spatial profile as well as on the frequency of the pulse excitation. The study of the ensemble with ideal memristor coupling is complemented by the exploration of the model implying the interaction through the memristor characterized by ‘forgetting’ the initial states over time. It is demonstrated through this approach that the dependence of the oscillation characteristics on the memristor initial states persists in the presence of the weak memristor imperfectness.

Floating Memristor and Inverse Memristor Emulators with Electronic Tuning

The work reports two different configurations to emulate the floating memristor and inverse memristor behavior. The presented circuits are based on a modified concept of active element VDTA (Voltage Differencing Transconductance Amplifier) termed as MVDTA. The reported floating memristor employs only a single MVDTA and single grounded capacitance. On the other end, the floating emulation circuit of inverse memristor emulator is based on two MVDTAs and single grounded capacitance. The behavior of the realized element for both the configurations can be tuned electronically through biasing voltage. Also, there is no employment of any commercial IC or external circuitry for multiplication of analogue voltages which is generally required to implement memristive elements. Along with the circuit implementations, mathematical properties of ideal memristor and inverse memristor considering both symmetric as well as nonsymmetric models are discussed. All the emulation circuits are verified by executing simulations using CMOS 0.18[Formula: see text]um process technique under PSPICE environment. The reported circuits are also realized using commercially available IC LM13700 and results are presented.

Resonant activation of resistive switching in ZrO2(Y) films

Local resistive switching (RS) in ZrO2(Y) films on conductive substrates has been studied using Conductive Atomic Force Microscopy (CAFM). Switching was performed by triangle voltage pulses with superimposed a high-frequency (HF) sinusoidal signal applied to the contact of the CAFM probe to the ZrO2(Y) film (together constituting a nanometer-sized virtual memristor). Earlier, the enhancement of the RS performance has been observed when the HF signal was superimposed onto the switching pulses. The effect was attributed to the resonant activation of the migration of oxygen ions via oxygen vacancies by an external alternating electric field. In the present study, this assumption was confirmed by measuring the frequency dependence of the difference between the probe currents in the low-resistance and high-resistance states with a maximum at about 5 kHz. This frequency corresponds to the characteristic one of the jumps of oxygen ions onto adjacent oxygen vacancies in ZrO2(Y) at 300 K. The experimental results were compared with the results of simulation based on the Chua model of an ideal memristor.

Suppression of ferroresonance using passive memristor emulator

Power system inherently consists of capacitance and inductance in its components. Equipment with saturable inductance and circuit capacitance provides circumstances of generating ferroresonance, resulting in overvoltage and overcurrent in the connected system. The effects of ferroresonance result in insulation failure and hence damage to the equipment is unavoidable. Though many devices are proposed for mitigating such circumstances, a promising technology of using memristors may provide better performance than others in the future. A memristor emulator using the N-channel JFET J310 is used in this work. Unlike other electronic components that replicate memristor properties, the chosen memristor emulator is a passive device since it does not need any external power supply. Simulation and experimental results verify the design of a memristor emulator and the characteristics of an ideal memristor. Experimental results prove that the memristor emulator can suppress the fundamental ferroresonance induced in a prototype single phase transformer. The results of the harmonic analysis also validate the memristor performance against the conventional technique.

Resistorless Memristor Emulator Using CFTA and Its Experimental Verification

This article presents a novel charge-controlled memristor emulator circuit. The proposed memristor emulator utilizes a single Current Follower Transconductance Amplifier (CFTA) as an active current mode analog building block and a grounded capacitor as a passive element. The circuit presented follows all the fingerprints of an ideal memristor. It operates in both incremental as well as decremental mode. The functional performance of the emulator circuit is verified at different operating frequencies and performs well up to 9 MHz . The theoretical and non-ideal analyses are verified for the proposed emulator. Moreover, Monte Carlo sampling and non-volatility analysis are performed to investigate the robustness of the emulator circuit. The functionality of the proposed model has been verified through PSPICE simulation using TSMC 0.18 $\mu m$ CMOS technology at the supply voltage of $\pm 1.2~V$ . The experimental confirmation of the presented circuit is also performed by building a breadboard micromodel using ICs CA3080 and AD844AN. Memristor based Chua’s circuit model is included as one of its applications.

Dynamic Analysis and Circuit Realization of a Novel No-Equilibrium 5D Memristive Hyperchaotic System with Hidden Extreme Multistability

In this paper, a novel no-equilibrium 5D memristive hyperchaotic system is proposed, which is achieved by introducing an ideal flux-controlled memristor model and two constant terms into an improved 4D self-excited hyperchaotic system. The system parameters-dependent and memristor initial conditions-dependent dynamical characteristics of the proposed memristive hyperchaotic system are investigated in terms of phase portrait, Lyapunov exponent spectrum, bifurcation diagram, Poincaré map, and time series. Then, the hidden dynamic attractors such as periodic, quasiperiodic, chaotic, and hyperchaotic attractors are found under the variation of its system parameters. Meanwhile, the most striking phenomena of hidden extreme multistability, transient hyperchaotic behavior, and offset boosting control are revealed for appropriate sets of the memristor and other initial conditions. Finally, a hardware electronic circuit is designed, and the experimental results are well consistent with the numerical simulations, which demonstrate the feasibility of this novel 5D memristive hyperchaotic system.

AN APPLICATION OF R-HiPIMS METHOD FOR TiO2- AND TiO2:Cu-BASED MEMRISTORS: CONTROLLING Cu DOPING USING DC PULSE METHOD

Nowadays, the High-Power Impulse Magnetron Sputtering (HiPIMS) as an additional technique to plasma-based sputtering, is applied to depositing or coating of thin films. HiPIMS is based on applying high-power and low-duty-cycle unipolar pulses to the magnetron target by a low repetition frequency, which are produced from the high ionization part of sputtered atoms by high discharge power. By applying voltage to substrate and bombarding it in the presence of an inert gas such as Ar, the growth of the film is controlled by the acceleration of the sputtered material across the highly dense plasma. To deposit compound materials, metal targets are sputtered with gases such as CH4, N2, O2, etc. or by Reactive HiPIMS (R-HiPIMS) techniques. The transparent metal oxide (TiO[Formula: see text] film depositions by R-HiPIMS are denser and have flatter surfaces due to a higher degree of crystallinity than other sputtering methods. The applicable potential of TiO2thin films and similar metal oxides on the ultra-high-density electronic devices due to the presence of oxygen deficiency, leads them to be chosen for memristor devices. As theory predicted, a current-controlled memristor is possible with metal–TiO2–metal structures. But stability and repeatability with high ON/OFF ratios remain as problems. A high ON/OFF ratio due to filament formation is revealed by Cu doping of TiO2thin films which leads to two state functions to be applicable for the traditional digital electronics. On the other hand, an ideal memristor has a potential for gray scale with no limitation. This approach has a big potential impact on data storage and computation in electronics. A new spotlight for this prediction is recognized by the high mobility of transition elements such as Cu in semiconductors. In this work, a nano-scale memristor based on Cu-doped TiO2is fabricated from metallic targets (i.e. Ti and Cu) by the R-HiPIMS method. Cu doping is synchronously controlled by using pulsed DC sputtering onto the TiO2structure. DC pulse duration and its frequency are used for adjusting the Cu doping concentration during the growth time of TiO2. The memristor properties of Cu–Pt–TiO2–p[Formula: see text]Si–Al and Cu–Pt–TiO2:Cu–p[Formula: see text]Si–Al devices are considered. The electrode change effect on the memristive properties and performance of Cu-doped memristor is investigated. The [Formula: see text]–[Formula: see text] characteristic of the Cu-doped memristor with Cu top electrode is recognized to be asymmetric in comparison with Cu-doped TiO2-based memristor with Pt top electrode. The structural, optical and electrical characterizations are carried out and preliminary findings are given in detail.

Ideal memristor based on viscous magnetization dynamics driven by spin torque

We show that ideal memristors—devices whose resistance is proportional to the charge that flows through them—can be realized using spin torque-driven viscous magnetization dynamics. The latter can be accomplished in the spin liquid state of thin-film heterostructures with frustrated exchange, where the memristive response is tunable by proximity to the glass transition, while current-induced Joule heating facilitates non-volatile operation and second-order memristive functionality beneficial for neuromorphic applications. Ideal memristive behaviors can be achieved in other systems characterized by viscous dynamics of physical, electronic, or magnetic degrees of freedom.

An Experimental Proof that Resistance‐Switching Memory Cells are not Memristors

AbstractIt has been suggested that all resistive‐switching memory cells are memristors. The latter are hypothetical, ideal devices whose resistance, as originally formulated, depends only on the net charge that traverses them. Recently, an unambiguous test has been proposed to determine whether a given physical system is indeed a memristor or not. Here, such a test is experimentally applied to both in‐house fabricated Cu‐SiO2 and commercially available electrochemical metallization cells. The results unambiguously show that electrochemical metallization memory cells are not memristors. Since the particular resistance‐switching memories employed in the study share similar features with many other memory cells, the findings refute the claim that all resistance‐switching memories are memristors. They also cast doubts on the existence of ideal memristors as actual physical devices that can be fabricated experimentally. The results then lead to formulate two memristor impossibility conjectures regarding the impossibility of building a model of physical resistance‐switching memories based on the memristor model.

Flux-Controlled Memristor Emulator and Its Experimental Results

A flux-controlled memristor emulator built with off-the-shelf electronic devices and based on a TiO2 model is presented in this article. The circuit proposed in this article uses the current mode approach based analog building blocks such as a second-generation current conveyor (CCII) and an operational transconductance amplifier (OTA) as an active element with few passive elements. The circuit shows a clear fingerprint of an ideal memristor. The offered emulator circuit can be made to operate in incremental and decremental modes and functions well up to 26.3 MHz. Nonvolatility, Monte Carlo sampling, and corner analysis simulations are executed to verify the robustness of the circuit. The functional verification of the presented circuit is performed using the 0.18- $\mu \text{m}$ CMOS parameter at a supply voltage of ±1.2 V. The experimental demonstration is carried out by making a prototype on a breadboard using ICs AD844AN and CA3080, which exhibits a good agreement with theoretical and simulation results. The layout of the circuit, which requires a total chip area of $75\times 70\,\,\mu \text{m}^{2}$ , is also created. Single/parallel combinations of a memristor, a high-pass filter, and a chaotic system are presented to demonstrate its application.

Microtubules as Sub-Cellular Memristors

Memristors represent the fourth electrical circuit element complementing resistors, capacitors and inductors. Hallmarks of memristive behavior include pinched and frequency-dependent I–V hysteresis loops and most importantly a functional dependence of the magnetic flux passing through an ideal memristor on its electrical charge. Microtubules (MTs), cylindrical protein polymers composed of tubulin dimers are key components of the cytoskeleton. They have been shown to increase solution’s ionic conductance and re-orient in the presence of electric fields. It has been hypothesized that MTs also possess intrinsic capacitive and inductive properties, leading to transistor-like behavior. Here, we show a theoretical basis and experimental support for the assertion that MTs under specific circumstances behave consistently with the definition of a memristor. Their biophysical properties lead to pinched hysteretic current–voltage dependence as well a classic dependence of magnetic flux on electric charge. Based on the information about the structure of MTs we provide an estimate of their memristance. We discuss its significance for biology, especially neuroscience, and potential for nanotechnology applications.

Tunable Memristor Emulator using Off-The-Shelf components

Abstract Emerging memristor technology is as of late drawing broad consideration due to its potential for several applications. But, the non-availability of solid-state memristive devices puts a practical limitation. So, this paper proposed the concept and design of a practical memristor emulator, which can be used to imitate the behaviour of the well-known ideal memristor model developed by the HP Lab. This circuit contains off-the-shelf components such as AD844, AD633, voltage variable resistor (VVR) and few passive components. This circuit provides voltage tunability, an additional advantage over current tunability, which requires a complex circuitry. All the fingerprints of nano-scale memristor behavior are validated by the derived mathematical relations and simulation verification. Further, the robustness of the circuit has been demonstrated for statistical (10% deviation in passive components) and environmental variations (10% deviation in supply voltages). Also, the proposed circuit has been tested for a wide temperature range. Eventually, the proposed circuit is compared with the previously published emulators to illustrate the advantages of the proposed design.

Periodically varied initial offset boosting behaviors in a memristive system with cosine memductance

A four-dimensional memristive system is constructed using a novel ideal memristor with cosine memductance. Due to the special memductance nonlinearity, this memristive system has a line equilibrium set (0, 0, 0, δ) located along the coordinate of the inner state variable of the memristor, whose stability is periodically varied with a change of δ. Nonlinear and one-dimensional initial offset boosting behaviors, which are triggered by not only the initial condition of the memristor but also other two initial conditions, are numerically uncovered. Specifically, a wide variety of coexisting attractors with different positions and topological structures are revealed along the boosting route. Finally, circuit simulations are performed by Power SIMulation (PSIM) to confirm the unique dynamical features.

Analysis and electronic implementation of an absolute memristor autonomous Van der Pol-Duffing circuit

In this paper, a memristor-based chaotic circuit is built by replacing the nonlinear resistor of a unified Van der Pol-Duffing circuit by an ideal and active flux-controlled memristor with an absolute value nonlinearity. The equilibrium points of the mathematical model describing the proposed absolute memristor Van der Pol-Duffing circuit are determined and their stabilities are analyzed thank to the Routh-Hurwitz criteria. The numerical simulations reveal that the proposed absolute memristor circuit exhibits reverse period-doubling to chaos, bistable one-scroll chaotic attractors, double-scroll chaotic attractor, bistable periodic attractors and antimonotonicity phenomenon. Moreover the proposed absolute memristor circuit is implemented in PSIM software package. The results found using the PSIM software package have a good qualitative agreement with those found during the numerical simulations.