Fast, Highly Flexible, and Transparent TaO_x-Based Environmentally Robust Memristors for Wearable and Aerospace Applications

Abstract

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 TaO x /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 TaO x 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.

Negative effect of cations out-diffusion and auto-doping on switching mechanisms of transparent memristor devices employing ZnO/ITO heterostructure

“…22,23 Several reports on memristor devices that employ ITO materials suggest that indium (In) and tin (Sn) atoms originated from the ITO electrode may benefit the switching mechanism in memristor devices. [24][25][26][27][28][29][30] However, in our study, we found that an excessive out-diffusion species from the ITO electrode leads to unstable switching; moreover, in contrast to some of those reports, Sn is found to be immobile that may not have a significant role in the switching mechanism.…”

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

“…5 In CBRAM, metal ions originated from the top electrode diffuses into the switching layer and form a metallic bridge which serves as a conduction path of electrons. 6,7,8 On the other hand, the conduction path in OxRAM is attributed to the formation of oxygen vacancy conducting filament. 9 Nevertheless, the formation of a hybrid conducting bridge consisting of metal atoms and oxygen vacancies was also reported.…”

Conductive Silver Grid Electrode for Flexible and Transparent Memristor Applications

“…As shown in Figure S8 in the Supporting Information, these memory devices exhibited different bending endurance against different bending radius (i.e., 6, 5, 4, and 3 mm), respectively. For r = 3 mm, this memory device cannot work after ≈25 times repetitive bending due to the cracks formation in the memory cell, [ 5c ] which resulted from the low failure strain of the organic Ag grids/WO 3 film. Based on the above experimental results, the Au/WO 3 /Ag grids/PET device showed fascinating electrical and mechanical characteristics for flexible transparent memristors application.…”

“…[ 4 ] Therefore, efforts to prepare flexible transparent RRAM also have generated a lot of interest. [ 5 ]…”