Flexible Ta2O5/WO3-based memristor synapse for wearable and neuromorphic applications

In this letter, Ta 2 O 5 /WO 3 double-layer wearable memristor synapse has excellent recognition accuracy (97%) for just 12 epochs compared to the single-layer device (83%). The insertion of an ultra-thin WO 3 layer modulates the oxygen vacancy distribution in Ta 2 O 5 and induces digital-to-analog switching behavior. Excellent AC endurance of (>10 9 cycles) under 2 mm extreme bending, a rapid speed (25 ns), reliable bending endurance for 10 4 cycles with 4 mm bending, stable retention (>10 6 s) up to 200°C, and water-resistant behavior are achieved. The potentiation, and depression having outstanding nonlinearity (0.64) is obtained. The Ta 2 O 5 /WO 3 design is a promising candidate for wearable neuromorphic applications due to its wearability, flexibility, lightweight, low cost and environmental friendly fabrication

Transformation of digital to analog switching in TaO_x-based memristor device for neuromorphic applications

An oxidizable metal diffusion barrier inserted between the active metal electrode and the switching layer decreases the electroforming voltage and enhances the switching stability and synaptic performances in TaOx-based conducting bridge memristor devices. The TiW barrier layer avoids an excessive metal ion diffusion into the switching layer, while the TiWOx interfacial layer is formed between the barrier and the switching layer. It modulates the oxygen vacancy distribution at the top interface and contributes to the formation and rupture of the metal ion-oxygen vacancy hybrid conducting bridge. We observe that the device that relies upon non-hybrid (metal ions only) conducting bridge suffers from poor analogous performance. Meanwhile, the device made with the barrier layer is capable of providing 2-bit memory and robust 50 stable epochs. TaOx also acts as resistance for suppressing and a thermal enhancement layer, which helps to minimize overshooting current. The enhanced analog device with high linear weight update shows multilevel cell characteristics and stable 50 epochs. To validate the neuromorphic characteristic of the devices, a simulated neural network of 100 synapses is used to recognize 10 × 10 pixel images

Fast, highly flexible, and transparent TaO_x-based environmentally robust memristors for wearable and aerospace applications

Memristor devices that can operate at high speed with high density and nonvolatile capabilities have great potential for the development of high data storage and robust wearable devices. However, in real-time, the performance of memristors is challenged by their instability toward harsh working conditions such as high temperature, extreme humidity, photo irradiation, and mechanical bending. Herein, we introduce a TaOx/AlN-based flexible and transparent memristor device having stable endurance under extreme 2 mm bending (for more than 107 cycles) with an ON/OFF ratio of more than 2 orders of magnitude at 25 ns rapid switching. This device exhibits excellent flexibility under extreme bending conditions (bending radius of 2 mm) even with intense ultraviolet (UV) radiation. A thin AlN insertion layer having low dielectric and high thermal conductivity plays a crucial role in improving the switching stability and device flexibility. In particular, the devices exhibit excellent minimum switching fluctuations under UV irradiation, >106 s nonvolatility retention at high temperature (135 °C), various gas ambient, and damp heat test (humidity 95.5%, 83 °C) because of the indium metal drift during the switching process and high bonding energy of Ta–O. Most importantly, direct observation of indium metal strongly anchored in the TaOx switching layer during the switching process is reported for the first time via transmission electron microscopy, which provides clear insights into the switching phenomenon. Furthermore, the results of electrical and material analyses explain that our facile device design has excellent potential for wearable and aerospace applications