arXiv subjects

N. G. Koudafokê

Publications and source records attributed to N. G. Koudafokê.

4 recordsLinked to original sources

arXiv2026

Electrothermal Compact Drift Model of TiO$_2$ Memristors: Verilog-A Implementation and Dimensionless Regime Mapping

Compact models of titanium-dioxide memristors used in circuit simulation commonly follow the drift formulation of Strukov \textit{et al.} and assume a constant ionic mobility, although oxygen-vacancy migration is thermally activated and Joule self-heating is unavoidable. We present ATDM (Arrhenius Thermally Activated Drift Model), a minimal electrothermal compact model that couples the drift equation to a lumped heat balance through an Arrhenius mobility. It adds one thermal state while preserving the electrical state variable, the relation $v=iR(x)$, and the isothermal limit. The model is implemented in \textsc{Verilog-A}, compiled with OpenVAF, and simulated as a device in \texttt{ngspice}, where it reproduces an independent reference implementation within $0.009\,\%$ of the peak voltage and recovers the isothermal excursion at zero activation energy. A dimensionless formulation introduces a thermal lag $\varepsilon$ and an effective switching number $Θ$. Across $2.5\times10^{5}$ simulations, $Θ$ orders the state-variable excursion over the tested quasi-static domain with a robust relative scatter of $4\,\%$ and no fitted constant, and the $(\varepsilon,Θ)$ regime map quantifies when the quasi-static thermal reduction remains valid. Under current drive, the stroboscopic map of the reduced model is proved to be strictly increasing, which excludes period-doubling and chaos in that reduction. Within the sampled ranges, a variance-based sensitivity analysis identifies the effective thermal resistance as a first-order contributor to self-heating, while separate capacitance sweeps show a weak influence of the thermal capacitance in the quasi-static regime. The results characterize the specified model with representative, uncalibrated parameters.

cond-mat.mtrl-sci↗

arXiv2026

Current-Gated Nonlinear Dynamics of a Self-Heating Memristor: an Electrothermal Extension of the Pickett Filamentary Model

Self-heating couples the electrical and thermal states of filamentary memristors. However, the widely used Pickett compact model of $TiO_2$ resistive switching is isothermal and therefore cannot capture the resulting electrothermal dynamics. We introduce the Arrhenius-Thermal Filamentary Model (ATFM), which extends Pickett's tunneling-gap kinetics by incorporating a dynamic heat balance and an Arrhenius-activated switching rate. The resulting electrothermal feedback produces a sharp current-gated transition: below a critical drive current, the tunneling gap undergoes a non-returning ratchet drift, whereas above it, exponential locking of the filament kinetics establishes a bounded, drive-locked electrothermal oscillation. Using a stroboscopic Poincaré map and the Floquet multipliers of the resulting period-$1$ orbit, we characterize this onset as a threshold-like orbit contraction rather than a classical local bifurcation. In the limit $E_a\to0$, ATFM recovers the isothermal Pickett dynamics to numerical precision, as verified against an independent reference implementation over amplitude, frequency, and activation-energy sweeps. A variance-based Sobol' analysis with bootstrap confidence intervals identifies the excitation amplitude as the dominant control parameter and the thermal resistance $R_{th}$, rather than the thermal capacitance $C_{th}$, as the leading thermal contributor. A geometry-dependent temperature constraint further reveals a non-monotonic operating window in which an intermediate active area maximizes the switching excursion. The predicted trajectories are reproduced by both a fully behavioral SPICE netlist and a Verilog-A/OSDI device implementation, making ATFM directly suitable for circuit simulation. Overall, ATFM reveals and realizes a self-heating-driven dynamical regime within the widely used Pickett filamentary framework.

nlin.CD↗

arXiv2026

Thermal Control of Hysteresis and Deterministic Chaos in a Memristive MEMS Resonator

We investigate the nonlinear dynamics of a thermo-electro-mechanically coupled memristive resonator comprising a doubly clamped Euler--Bernoulli microbeam, an RLC circuit, and a TiO$_2$ memristor with temperature-dependent ionic mobility governed by Mott and Efros--Shklovskii hopping conduction. The dynamics are analyzed using two-dimensional parameter-space maps, bifurcation diagrams, Lyapunov exponents, reconstructed attractors, Poincaré sections, Grassberger--Procaccia correlation-dimension analysis, empirical mode decomposition, the Hilbert--Huang spectrum, and electro-memristive hysteresis. Parameter-space maps reveal predominantly quasi-periodic and deterministic chaotic regimes without stable phase-locked periodic states. Bifurcation analyses show that the beam length and excitation frequency govern the dynamics through the frequency ratio $r_ω=ω_0/ω_b$, whereas the excitation current mainly controls the oscillation amplitude and chaotic intensity. Under fixed operating conditions, the asymptotic regime depends on the initial conditions, and complementary diagnostics identify the thermo-memristive subsystem as the primary source of the nonlinear complexity, subsequently transmitted to the microbeam through electromechanical coupling. Temperature continuously reorganizes the electro-memristive hysteresis through the chain $T \to σ(T) \to M(w,T) \to i_m(t) \to w(t)$. The hysteresis area evolves non-monotonically with temperature, revealing a configuration-dependent optimal thermo-memristive operating point. These findings highlight temperature, beam length, and electrical excitation as complementary control parameters for tailoring thermo-memristive memory, deterministic chaos, and nonlinear dynamics in thermo-active MEMS, with potential applications in neuromorphic sensing and chaos-based secure communication.

nlin.CD↗

arXiv2026

Characterization of Chaotic and Homogeneous coexisting dynamics of a Memristive Thermo-Controlled MEMS

This work presents the mathematical modeling and numerical investigation of a thermo-controlled Micro-Electro-Mechanical System (MEMS) obtained by coupling an HP memristor with mechanical and electrical resonators. Using the linear drift HP memristor model, the nonlinear electromechanical dynamics are analyzed through Lyapunov exponents, bifurcation diagrams, phase portraits, recurrence plots, Poincaré sections, and Fourier spectra. The results reveal parameter-dependent transitions between quasi-periodic and chaotic oscillations, as well as signatures of coexisting dynamical regimes. A systematic investigation of the intrinsic memristor parameters, namely the ON-state resistance Ron, the OFF-state resistance Roff, the oxide thickness D, and the ionic mobility μ_v, demonstrates that memristive effects strongly influence oscillation amplitudes, resonance frequencies, and nonlinear transitions within the coupled thermo-electro-mechanical system. The state-dependent memristance dynamically modulates the electromechanical coupling and redistributes energy between the electrical and mechanical resonators, thereby generating complex oscillatory responses. In addition, the influence of temperature-sensitive memristive parameters is qualitatively examined through variations of the ionic mobility and resistive states. The results indicate that thermal variations can modify both oscillation amplitudes and dynamical regimes, potentially inducing transitions between quasi-periodic and chaotic behaviors. A comparative discussion with Josephson-junction-based MEMS architectures highlights the operational flexibility and room-temperature compatibility of the HP memristor model for thermo-electro-mechanical applications. These findings suggest promising prospects for adaptive nonlinear oscillators, thermo-sensitive sensors, and chaos-driven electromechanical systems.

nlin.CD↗