High-Performance Single-Active-Layer Memristor Based on an Ultrananocrystalline Oxygen-Deficient TiOx Film

Performance Regulation of a ZnO/WOx-Based Memristor and Its Application in an Emotion Circuit

The development of a memristor is very important for artificial intelligence and new electronic circuits. In this work, Ag(Al)/ZnO/WO_x/FTO memristors are fabricated by magnetron sputtering, and the device performance is further improved through annealing and oxygen supply during sputtering. The experimental data show that the FTO/WO_x/ZnO-O₂/Ag memristor has the largest high resistance state (HRS)/low resistance state (LRS) resistance ratio and the best durability. Through data fitting and analysis, the switching mechanism of memristors with different top electrodes is investigated. Furthermore, the physical model of the best performance memristor was established by Simulink, and an emotion-monitoring circuit was constructed on this basis. The circuit can be used to monitor and record the mood changes, and the feedback of the emotion monitoring can be fed back to the user to help them adjust the mood.

Induced Complementary Resistive Switching in Forming-Free TiOx/TiO2/TiOx Memristors

The undesirable sneak current path is one of the key challenges in high-density memory integration for the emerging cross-bar memristor arrays. This work demonstrates a new heterojunction design of oxide multilayer stacking with different oxygen vacancy contents to manipulate the oxidation state. We show that the bipolar resistive switching (BRS) behavior of the Pt/TiO_x/Pt cross-bar structure can be changed to complementary resistive switching (CRS) by introducing a thin TiO₂ layer in the middle of the TiO_x layer to obtain a Pt/TiO_x/TiO₂/TiO_x/Pt device architecture with a double-junction active matrix. In contrast to the BRS in a single-layer TiO_x matrix, the device with a double-junction matrix remains in a high-resistance state in the voltage range below the SET voltage, which makes it an efficient structure to overcome the sneak path constraints of undesired half-selected cells that lead to incorrect output reading. This architecture is capable of eliminating these half-selected cells between the nearby cross-bar cells in a smaller programming voltage range. A simplified model for the switching mechanism can be used to account for the observed high-quality switching performance with excellent endurance and current retention properties.

Transparent HfO x -based memristor with robust flexibility and synapse characteristics by interfacial control of oxygen vacancies movement

Hafnium oxides (HfO _x ) based flexible memristors were fabricated on polyethylene naphtholate (PEN) substrates to simulate a variety of bio-synapse functions. By optimizing the manufacturing conditions of electrode and active films, it is proved that the TiN/HfO _x /W/ITO/PEN bilayer device has robust flexibility and can still be modulated after 2000 times of bending. The memristor device exhibits better symmetrical and linear characteristics with excellent uniformity at lower programming power consumption (∼38 μW). In addition, the essential synaptic behaviors have further been achieved in the devices, including the transition from short-term plasticity to long-term plasticity and spike time-dependent plasticity. Through the analysis of I-V curves and XPS data, a switching mechanism based on HfO _x /W interface boundary drift is constructed. It is revealed that the redox reaction caused by W intercalation can effectively regulate the content of oxygen vacancy in HfO _x . At the same time, bias-induced interfacial reactions will regulate the movement of oxygen vacancies, which emulates bio-synapse functions and improves the electrical properties of the device.

Programmable, electroforming-free TiOx/TaOx heterojunction-based non-volatile memory devices

Electroforming-free resistive switching in memristors is essential to reliably achieving the performance of high switching speed, high endurance, good signal retention, and low power consumption expected for next-generation computing devices. Although there have been various approaches to resolve the issues observed with the electroforming process in oxide-based memory devices, most of them end up having high SET and RESET voltages and short lifetimes. We present a heterojunction interface of oxygen-vacancy-defect-rich ultrananocrystalline TiOx and TaOx films used as the switching matrix, which enables high-quality electroforming-free switching with a much lower programming voltage (+0.5-0.8 V), a high endurance of over 104 cycles and good retention performance with an estimated device lifetime of over 10 years. The electroforming-free switching behavior is governed by migration of oxygen vacancies driven by electric field localization that is imposed by the ultrananocrystalline nature of the TaOx film, serving as the switching matrix, with the TiOx film serving as an additional oxygen vacancy source to reduce the overall resistivity of TaOx and provide low-bias rectification. The ability to perform electroforming-free resistive switching along with excellent switching repeatability and retention capabilities for various digital and analog programmable voltages enables high scalability and large density integration of the cross-bar ReRAM framework.

Resistive Switching Memory Devices Based on Body Fluid of Bombyx mori L

Resistive switching memory devices are strong candidates for next-generation data storage devices. Biological memristors made from renewable natural biomaterials are very promising due to their biocompatibility, biodegradability, and ecological benignity. In this study, a nonvolatile memristor was fabricated using the body fluid of Bombyx mori as the dielectric layer. The developed Al/Bombyx mori body fluid film/indium tin oxide (ITO) biomemristor exhibited bipolar resistive switching characteristics with a maximum on/off current ratio greater than 10⁴. The device showed a retention time of more than 1 × 10⁴ s without any signs of deterioration, thus proving its good stability and reliability. The resistive switching behavior of the Al/Bombyx mori body fluid film/ITO biological memristor is driven by the formation and breakage of conductive filaments formed by the migration of oxygen ions. This study confirms that Bombyx mori body fluid, a 100% natural, inexpensive, and abundant material, is a potential candidate as a nonvolatile biomemristor material with broad application prospects.