Controllable high-performance memristors based on 2D Fe2GeTe3oxide for biological synapse imitation.

Memristors are an important component of the next-generation artificial neural network, high computing systems, etc. In the past, two-dimensional materials based memristors have achieved a high performance and low power consumption, though one at the cost of the other. Furthermore, their performance can not be modulated frequently once their structures are fixed, which remains the bottleneck in the development. Herein, a series of forming free memristors are fabricated with the same Cu/Fe3GeTe2oxide/Fe3GeTe2/Al structure, yet the On/Off ratio and set voltage is modulated continuously by varying the oxidation time during fabrication. With an optimal oxidation time, a large On/Off ratio (1.58 × 103) and low set voltage (0.74 V) is achieved in a single device. The formation and rapture of Al conductive filaments are found to be responsible for the memristors, and the filaments density and the cross-section area increase with the increase of current compliance, which achieves a higher On/Off ratio. The memristor can imitate basic biological synaptic functions using voltage pulses, demonstrating the potential for low-power consuming neuromorphic computing applications.

Tunable asymmetric magnetoresistance in an Fe3GeTe2/graphite/Fe3GeTe2 lateral spin valve.

van der Waals (vdW) ferromagnetic heterojunctions, characterized by an ultraclean device interface and the absence of lattice matching, have emerged as indispensable and efficient building blocks for future spintronic devices. In this study, we present a seldom observed antisymmetric magnetoresistance (MR) behavior with three distinctive resistance states in a lateral van der Waals (vdW) structure comprising Fe3GeTe2 (FGT)/graphite/FGT. In contrast to traditional spin valves governed by the magnetization configurations of ferromagnetic electrodes (FEs), this distinct feature can be attributed to the interaction between FGT and the FGT/graphite interface, which is primarily influenced by the internal spin-momentum locking effect. Furthermore, modulation of the MR behavior is accomplished by employing the coupling between antiferromagnetic and ferromagnetic materials to adjust the coercive fields of two FEs subsequent to the in situ growth of an FGT oxide layer on FGT. This study elucidates the device physics and mechanism of property modulation in lateral spin valves and holds the potential for advancing the development of gate-tunable spintronic devices and next-generation integrated circuits.

Proximity Effect-Induced Magnetoresistance Enhancement in a Fe3GeTe2/NbSe2/Fe3GeTe2 Magnetic Tunnel Junction.

The coupling between van der Waals-layered magnetic and superconducting materials holds the possibility of revealing novel physical mechanisms and realizing spintronic devices with new functionalities. Here, we report on the realization and investigation of a maximum ∼17-fold magnetoresistance (MR) enhancement based on a vertical magnetic tunnel junction of Fe3GeTe2 (FGT)/NbSe2/FGT near the NbSe2 layer's superconducting critical temperature (TC) of 6.8 K. This enhancement is attributed to the band splitting in the atomically thin NbSe2 spacer layer induced by the magnetic proximity effect on the material interfaces. However, the band splitting is strongly suppressed by the interlayer coupling in the thick NbSe2 layer. Correspondingly, the device with a thick NbSe2 layer displays no MR increase near TC but a current dependent on transport properties at extremely low temperatures. This work carefully investigates the mechanism of MR enhancement, paving an efficient way for the modulation of spintronics' properties and the achievement of spin-based integrated circuits.

Toward Controlled Electrical Stimulation for Wound Healing Based on a Precision Layered Skin Model.

Bioelectricity performs vital functions in the human body. When skin is damaged, the endogenous electric field will orient toward the center of wounds, guiding the migration of relevant cells and stimulating the secretion of growth factors. A large number of experiments have indicated that external electric stimuli have significant positive influences on wound healing. However, the mechanism of this therapy remains unclear, and the current selection of parameters for electric stimuli tends to be arbitrary or empirical, making it inefficient and ineffective. From the perspective of bioelectricity and electrochemistry, the mechanism of electric stimuli is investigated in detail based on a sectioned multilayer model in this work, and an electric stimuli window is obtained in terms of frequency, duty cycle, voltage, and electric charge and verified experimentally. This model provides general guidance for the optimization of electrical stimuli therapy for wound healing.

Liquid metal-based electrical interconnects and interfaces with excellent stability and reliability for flexible electronics.

Stable and reliable electrical properties of interconnects and interfaces between flexible/stretchable and rigid materials/components are essential for the practical applications of flexible electronic devices and systems; traditional metal thin films and hard solder interconnects and interfaces can no longer meet these requirements. As an emerging soft conductive material, liquid metal has the advantages of high stretchability, flexibility, etc. over other soldering materials, and it has been used in interconnects and interfaces for some flexible electronics. In this study, we report a detailed investigation on the reliability and stability of liquid metal-based interconnects/interfaces under various mechanical deformations, including extension, bending, torsion, high frequency vibration and high temperature operation; we also compared the results with those of interconnects and interfaces using silver paste, the most commonly used solder for flexible electronics. The results show that liquid metal interconnects and interfaces maintain high conductivity under severe elongation up to 95% and 130%, upon bending with a curvature radius as low as ∼1.5 mm, and upon twisting up to 360°; meanwhile, interconnects and interfaces with silver paste filler lose electrical conductivity at elongations of 0.6% and 60%, respectively. Liquid metal interconnects and interfaces show superior performance to silver paste interconnects and interfaces because liquid metal can be re-shaped to make good contact with objects, while the silver paste becomes solid and rigid once dried and thus loses contact with other objects under deformation.