Localized Conduction Channels in Memristors.

Since the early 2000s, the impending end of Moore's scaling, as the physical limits to shrinking transistors have been approached, has fueled interest in improving the functionality and efficiency of integrated circuits by employing memristors or two-terminal resistive switches. Formation (or avoidance) of localized conducting channels in many memristors, often called "filaments", has been established as the basis for their operation. While we understand some qualitative aspects of the physical and thermodynamic origins of conduction localization, there are not yet quantitative models that allow us to predict when they will form or how large they will be.

Enhancing Uniformity, Read Voltage Margin, and Retention in Three-Dimensional and Self-Rectifying Vertical Pt/TaO/AlO/TiN Memristors.

This study introduces a TaO-based self-rectifying memristor (SRM) with an AlO interfacial layer adopted to improve switching uniformity, read voltage margin, and long-term retention. The Pt/TaO/AlO/TiN (PTAT) device exhibits a 10 rectification ratio, 10 on/off ratio, 2 × 10 endurance, and retention of 10 s at 150 °C. A 3-layer 4 × 4 vertical resistive random access memory structure exhibits uniform switching parameters.

Memristors with Tunable Volatility for Reconfigurable Neuromorphic Computing.

Neuromorphic computing promises an energy-efficient alternative to traditional digital processors in handling data-heavy tasks, primarily driven by the development of both volatile (neuronal) and nonvolatile (synaptic) resistive switches or memristors. However, despite their energy efficiency, memristor-based technologies presently lack functional tunability, thus limiting their competitiveness with arbitrarily programmable (general purpose) digital computers. This work introduces a two-terminal bilayer memristor, which can be tuned among neuronal, synaptic, and hybrid behaviors.

True random number generation using the spin crossover in LaCoO.

While digital computers rely on software-generated pseudo-random number generators, hardware-based true random number generators (TRNGs), which employ the natural physics of the underlying hardware, provide true stochasticity, and power and area efficiency. Research into TRNGs has extensively relied on the unpredictability in phase transitions, but such phase transitions are difficult to control given their often abrupt and narrow parameter ranges (e.g.

Implementation of Bayesian networks and Bayesian inference using a CuTe/HfO/Pt threshold switching memristor.

Bayesian networks and Bayesian inference, which forecast uncertain causal relationships within a stochastic framework, are used in various artificial intelligence applications. However, implementing hardware circuits for the Bayesian inference has shortcomings regarding device performance and circuit complexity. This work proposed a Bayesian network and inference circuit using a CuTe/HfO/Pt volatile memristor, a probabilistic bit neuron that can control the probability of being 'true' or 'false.

Tunable stochastic memristors for energy-efficient encryption and computing.

Information security and computing, two critical technological challenges for post-digital computation, pose opposing requirements - security (encryption) requires a source of unpredictability, while computing generally requires predictability. Each of these contrasting requirements presently necessitates distinct conventional Si-based hardware units with power-hungry overheads. This work demonstrates CuTe/HfO ('CuTeHO') ion-migration-driven memristors that satisfy the contrasting requirements.

2Memristor-1Capacitor Integrated Temporal Kernel for High-Dimensional Data Mapping.

Compact but precise feature-extracting ability is core to processing complex computational tasks in neuromorphic hardware. Physical reservoir computing (RC) offers a robust framework to map temporal data into a high-dimensional space using the time dynamics of a material system, such as a volatile memristor. However, conventional physical RC systems have limited dynamics for the given material properties, restricting the methods to increase their dimensionality.

Heterogeneous reservoir computing in second-order TaO/HfO memristors.

Multiple switching modes in a TaO/HfO memristor are studied experimentally and numerically through a reservoir computing (RC) simulation to reveal the importance of nonlinearity and heterogeneity in the RC framework. Unlike most studies, where homogeneous reservoirs are used, heterogeneity is introduced by combining different behaviors of the memristor units. The chosen memristor for the reservoir units is based on a TaO/HfO bilayer, in which the conductances of the TaO and HfO layers are controlled by the oxygen vacancies and deep/shallow traps, respectively, providing both volatile and non-volatile resistive switching modes.

Time-varying data processing with nonvolatile memristor-based temporal kernel.

Recent advances in physical reservoir computing, which is a type of temporal kernel, have made it possible to perform complicated timing-related tasks using a linear classifier. However, the fixed reservoir dynamics in previous studies have limited application fields. In this study, temporal kernel computing was implemented with a physical kernel that consisted of a W/HfO/TiN memristor, a capacitor, and a resistor, in which the kernel dynamics could be arbitrarily controlled by changing the circuit parameters.

Electroforming-Free Bipolar Resistive Switching in GeSe Thin Films with a Ti-Containing Electrode.

Chalcogenide materials have been regarded as strong candidates for both resistor and selector elements in passive crossbar arrays owing to their dual capabilities of undergoing threshold and resistance switching. This work describes the bipolar resistive switching (BRS) of amorphous GeSe thin films, which used to show Ovonic threshold switching (OTS) behavior. The behavior of this new functionality of the material follows filament-based resistance switching when Ti and TiN are adopted as the top and bottom electrodes, respectively.

Atomic layer deposition of GeSe films using HGeCl and [(CH)Si]Se with the discrete feeding method for the ovonic threshold switch.

The ovonic threshold switch (OTS) based on the voltage snapback of amorphous chalcogenides possesses several desirable characteristics: bidirectional switching, a controllable threshold voltage (V ) and processability for three-dimensional stackable devices. Among the materials that can be used as OTS, GeSe has a strong glass-forming ability (∼350 °C crystallization temperature), with a simple binary composition. Described herein is a new method of depositing GeSe films through atomic layer deposition (ALD), using HGeCl and [(CH)Si]Se as Ge and Se precursors, respectively.