Artificial Neural Synapses Based on Microfluidic Memristors Prepared by Capillary Tubes and Ionic Liquid.

Neuromorphic simulation, i.e., the use of electronic devices to simulate the neural networks of the human brain, has attracted a lot of interest in the fields of data processing and memory. This work provides a new method for preparing a 1,3-dimethylimidazolium nitrate ([MMIm][NO3]:H2O) microfluidic memristor that is ultralow cost and technically uncomplicated. Such a fluidic device uses capillaries as memory tubes, which are structurally similar to interconnected neurons by simple solution treatment. When voltage is applied, the transmission of anions and cations in the tube corresponds to the release of neurotransmitters from the presynaptic membrane to the postsynaptic membrane. The change of synaptic weights (plasticity) also can be simulated by the gradual change of conductance of the fluid memristor. The learning process of microfluidic memristors is very obvious, and the habituation and recovery behaviors they exhibit are extremely similar to biological activities, representing its good use for simulating neural synapses.

CuxS nanosheets with controllable morphology and alignment for memristor devices.

In electrochemical metallization memristor, the performance of resistive switching (RS) is influenced by the forming and fusing of conductive filaments within the dielectric layer. However, the growth of filaments, mostly, is unpredictable and uncontrollable. For this reason, to optimize ions migration paths in the dielectric layer itself in the Al/CuxS/Cu structure, uniform CuxS nanosheets films have been synthesized using anodization for various time spans. And the Al/CuxS/Cu devices show a low operating voltage of less than 0.3 V and stable RS performance. At the same time, a reversible negative differential resistance (NDR) behavior is also demonstrated. And then, the mechanism of repeatable coexistence of RS effect and NDR phenomenon is investigated exhaustively. Analyses suggest that the combined physical model of space-charge limited conduction mechanism and conductive filaments bias-induced migration of Cu ions within the CuxS dielectric layer is responsible for the RS operation, meanwhile, a Schottky barrier caused by copper vacancy at the CuxS/Cu interface is demonstrated to explain the NDR phenomenon. This work will develop a new way to optimize the performance of non-volatile memory with multiple physical attributes in the future.

Low-temperature liquid phase reduced TiO2 nanotube arrays: synergy of morphology manipulation and oxygen vacancy doping for enhancement of field emission.

The partially reduced TiO(2) nanotube arrays (TNAs) are prepared via an uncomplicated and low-cost liquid phase reduction strategy using NaBH(4) as the reducing agent. By controlling and adjusting the reduction temperatures from 30 to 90 °C, the reduction treatment can not only change their surface morphology but also introduce oxygen vacancies into them, resulting in an optimized morphology, elevated Fermi-level, reduced effective work function and improved conductivity of the TNAs. Meanwhile, the thermal and long-term stability of oxygen vacancy are also investigated, indicating that the oxygen vacancies retain long-term stability from room temperature up to 150 °C. More interesting, partially reduced TNAs show drastically enhanced field emission (FE) performances including substantially decreased turn-on field from 18.86 to 1.53 V µm(-1), a high current density of 4.00 mA cm(-2) at 4.52 V µm(-1), and an excellent FE stability and repeatability. These very promising results are attributed to the combination of the optimized morphology and introduced oxygen vacancies, which can increase FE sites, reduce effective work function and increase conductivity.

Enhanced field emission from hydrogenated TiO2 nanotube arrays.

The field emission (FE) properties of TiO(2) nanotube arrays (TNAs) synthesized by anodization are dramatically improved after hydrogenation at various temperatures in a range of 400-550 °C. Compared with pristine TNAs, the turn-on fields of hydrogenated TNAs (H:TNAs) are significantly decreased from 18.23 to 1.75 V µm(-1), and closely related to hydrogenation temperature. Importantly, the optimized sample of H:TNAs prepared at 550 °C shows excellent FE performances involving both a low turn-on field of 1.75 V µm(-1), a high current density of 4.0 mA cm(-2) at 4.50V µm(-1), and a remarkable FE stability over 480 min. The substantially enhanced FE properties can be attributed to the combination of a typical tubular morphology, a reduced work function and the improved conductivity of H:TNAs.