The intrinsic stochasticity of the memristor can be used to generate true random numbers, essential for non-decryptable hardware-based security devices. Here, we propose a novel and advanced method to generate true random numbers utilizing the stochastic oscillation behavior of a NbOx mott memristor, exhibiting self-clocking, fast and variation tolerant characteristics. The random number generation rate of the device can be at least 40 kb s−1, which is the fastest record compared with previous volatile memristor-based TRNG devices. Also, its dimensionless operating principle provides high tolerance against both ambient temperature variation and device-to-device variation, enabling robust security hardware applicable in harsh environments.

Valence change-type resistance switching behaviors in oxides can be understood by well-established physical models describing the field-driven oxygen vacancy distribution change. In those models, electroformed residual oxygen vacancy filaments are crucial as they work as an electric field concentrator and limit the oxygen vacancy movement along the vertical direction. Therefore, their movement outward by diffusion is negligible. However, this situation may not be applicable in the electroforming-free system, where the field-driven movement is less prominent, and the isotropic oxygen vacancy diffusion by concentration gradient is more significant, which has not been given much consideration in the conventional model. Here, we propose a modified physical model that considers the change in the oxygen vacancies’ charged state depending on their concentrations and the resulting change in diffusivity during switching to interpret the electroforming-free device behaviors. The model suggests formation of an hourglass-shaped filament constituting a lower concentration of oxygen vacancies due to the fluid oxygen diffusion in the thin oxide. Consequently, the proposed model can explain the electroforming-free device behaviors, including the retention failure mechanism, and suggest an optimized filament configuration for improved retention characteristics. The proposed model can plausibly explain both the electroformed and the electroforming-free devices. Therefore, it can be a standard model for valence change memristors.

NbO x -based Mott memristors exhibit fast threshold switching behaviors, making them suitable for spike generators in neuromorphic computing and stochastic clock generators in security devices. In these applications, a high output spike amplitude is necessary for threshold level control and accurate signal detection. Here, we propose a materialwise solution to obtain the high amplitude spikes by inserting Au nanodots into the NbO x device. The Au nanodots enable increasing the threshold voltage by modulating the oxygen contents at the electrode-oxide interface, providing a higher ON current compared to nanodot-free NbO x devices. Also, the reduction of the local switching region volume decreases the thermal capacitance of the system, allowing the maximum spike amplitude generation. Consequently, the Au nanodot incorporation increases the spike amplitude of the NbO x device by 6 times, without any additional external circuit elements. The results are systematically supported by both a numerical model and a finite-element-method-based multiphysics model.

Cu interconnects suffer from increased resistance and poor reliability at a sub-10 nm width. Ru and Mo have been highlighted recently as the next interconnection material candidate due to their various advantages over Cu; they have lower resistance than Cu at sub-10 nm, do not diffuse into SiO2, and are etchable. Here, we evaluated the electromigration (EM) reliability of Ru and Mo to confirm their feasibility for the next-generation interconnection. The activation energy for EM failure is calculated by measuring the mean time to failure (MTTF) of film and wire structures while factoring in temperature increases with thermal coefficient of resistance (TCR) measurements. In addition, we investigate the EM properties in terms of resistivity-increasing parameters that originate from geometry and additional fabrication processes. Furthermore, we evaluate the EM performance in terms of electrochemical potential. Our findings confirm the feasibility of Ru as a promising candidate for next-generation interconnection applications, providing enhanced reliability compared to conventional Cu interconnects.

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Heat dissipation is a natural consequence of operating any electronic system. In nearly all of computing, such heat is minimized by design and discarded via cooling, while some post-digital electronics (such as phase-change memories) utilize only the static electrical outcome of such heat dissipation within a single device to represent information. Thus, neither the naturally produced heat energy nor its dynamics are directly used for computing. Here we demonstrate electronic NbOx Mott neurons integrated on a biocompatible flexible organic substrate, designed to exploit both the thermal dynamics of the Mott transition and the dynamics of thermal interactions with the organic substrate, to exhibit 18 bio-mimetic neuronal behaviors and frequency-based nociception (sensing of noxious stimuli) within a single component. Further, multiple Mott neurons can spatiotemporally communicate purely via their thermal dynamics, which we use for graph optimization by consuming over 107× lower energy compared to the best digital processors. Thus, we show that naturally produced heat in electronic systems and its dynamics can be used directly to encode and process information, thereby enabling a higher-complexity energy efficient and radically novel mixed-physics computing primitive.

Energy-based computing is a promising approach for solving NP-hard problems. Probabilistic computing using pbits, which can be fabricated through the semiconductor process and integrated with conventional processing units, can be an efficient candidate for fulfilling these demands. Here, we propose a novel pbit unit comprising a NbOx mott memristor-based oscillator, capable of generating probabilistic bits in a self-clocking manner. The noise-induced mott transition causes the probabilistic behavior, which can be effectively modeled using a multi-noise-induced stochastic process around the mott transition temperature. We demonstrate a memristive Boltzmann machine based on our proposed pbit and validate its feasibility by solving NP-hard problems. Furthermore, we propose a streamlined operation methodology that considers the autocorrelation of individual bits, enabling energy-efficient high-performance probabilistic computing.

The intrinsic stochasticity of the memristor can be used to generate true random numbers, essential for non-decryptable hardware-based security devices. Here we propose a novel and advanced method to generate true random numbers utilizing the stochastic oscillation behavior of a NbOx mott memristor, exhibiting self-clocking, fast and variation tolerant characteristics. The random number generation rate of the device can be at least 40 kbs-1, which is the fastest record compared with previous volatile memristor-based TRNG devices. Also, its dimensionless operating principle provides high tolerance against both ambient temperature variation and device-to-device variation, enabling robust security hardware applicable in harsh environments.