Lithium ion trapping mechanism of SiO2 in LiCoO2 based memristors

Stable and Tunable Quantum Conductance in Spider-Silk-like Synaptic Device for Neurocomputing

The quantum conductance (QC) behaviors in synaptic devices with stable and tunable conductance states are essential for high-density storage and brain-like neurocomputing (NC). In this work, inspired by the discontinuous transport of fluid in spider silk, a synaptic device composed of a silicon oxide nanowire network embedded with silicon quantum dots (Si-QDs@SiOx) is designed. The tunable QC behaviors are achieved in both the SET and RESET processes, and the QC states exhibit stable retention time exceeding 104 s in the synaptic device and show stable reproducibility after an interval of two months. The synaptic plasticity, including long-term potentiation/depression and Pavlovian conditioning function, is simulated based on the tunable conductance. The mechanism of stable and tunable QC behaviors is analyzed and clarified by beading effect of spider silk in Si-QDs@SiOx nanowires structure. The digit recognition capability of the device is evaluated by simulation using an artificial neural network consisting of the Si-QDs@SiOx-based synaptic device. These results provide insights into the development of neurocomputing systems with high classification accuracy.

A conversion-type lithium artificial synapse with dispersed nano-silica fabricated by UV-curing method

The rapid growth of information puts forward new requirements for computer including denser memory capacity and faster response beyond the traditional von Neumann architecture. One promising strategy is to employ novel computing devices such as artificial synapses (AS). Here, an Au/LPSE-SiO₂/Si AS (LPSE-SiO₂AS) with a simple sandwich structure was fabricated by UV curing. LPSE-SiO₂AS emulated synaptic plasticity including excitatory postsynaptic current, paired-pulse facilitation, and spike-dependent plasticity. It also simulated the memory strengthening and forgetting analogue to biological system. The realization of synaptic plasticity is due to the homogeneously dispersed nano-silica in LPSE, which acts as lithium ions trapping center and conducts a reversible electrochemical conversion reaction with Li ions with pulse stimulation. These results indicate the potential for LPSE-SiO₂AS in future large-scale integrated neuromorphic networks.

Evidence of Biorealistic Synaptic Behavior in Diffusive Li-based Two-terminal Resistive Switching Devices

Following the recent advances in artificial synaptic devices and the renewed interest regarding artificial intelligence and neuromorphic computing, a new two-terminal resistive switching device, based on mobile Li⁺ ions is hereby explored. Emulation of neural functionalities in a biorealistic manner has been recently implemented through the use of synaptic devices with diffusive dynamics. Mimicking of the spontaneous synaptic weight relaxation of neuron cells, which is regulated by the concentration kinetics of positively charged ions like Ca²⁺, is facilitated through the conductance relaxation of such diffusive devices. Adopting a battery-like architecture, using LiCoO₂ as a resistive switching cathode layer, SiO_x as an electrolyte and TiO₂ as an anode, Au/LiCoO₂/SiO_x/TiO₂/p⁺⁺-Si two-terminal devices have been fabricated. Analog conductance modulation, via voltage-driven regulation of Li⁺ ion concentration in the cathode and anode layers, along with current rectification and nanobattery effects are reported. Furthermore, evidence is provided for biorealistic synaptic behavior, manifested as paired pulse facilitation based on the summation of excitatory post-synaptic currents and spike-timing-dependent plasticity, which are governed by the Li⁺ ion concentration and its relaxation dynamics.

Sputtered LiCoO2 Cathode Materials for All-solid-state Thin-film Lithium Microbatteries

This review article presents the literature survey on radio frequency (RF)-magnetron sputtered LiCoO₂ thin films used as cathode materials in all-solid-state rechargeable lithium microbatteries. As the process parameters lead to a variety of texture and preferential orientation, the influence of the sputtering conditions on the deposition of LiCoO₂ thin films are considered. The electrochemical performance is examined as a function of composition of the sputter Ar/O₂ gas mixture, gas flow rate, pressure, nature of substrate, substrate temperature, deposition rate, and annealing temperature. The state-of-the-art of lithium microbatteries fabricated by the rf-sputtering method is also reported.

Stability and Repeatability of a Karst-like Hierarchical Porous Silicon Oxide-Based Memristor

A memristor architecture based on porous oxide materials has the potential to be used in artificial synaptic devices. Herein, we present a memristor system employing a karst-like hierarchically porous (KLHP) silicon oxide structure with good stability and repeatability. The KLHP structure prepared by an electrochemical process and thermal oxidation exhibits high ON-OFF ratios up to 10⁵ during the endurance test, and the data can be maintained for 10⁵ s at a small read voltage 0.1 V. The mechanism of lithium ion migration in the porous silicon oxide structure has been discussed by a simulated model. The porous silicon oxide-based memristor is very promising because of the enhanced performance as well as easily accessed neuromorphic computing.