Electrical and Electrochemical Investigations on Copper Oxide-Based Monolayer and Bilayer Memristive Devices

Resistive switching (RS) devices are the best choice for nonvolatile memory storage and neuromorphic computing applications due to their ease of fabrication, low power consumption, and long stability. In the past, monolayer metal-oxide-based RS devices were studied to achieve the desired memory and artificial synaptic characteristics. However, very few studies were conducted on bilayer RS devices to get the desired RS characteristics. Given this, we fabricated bilayer metal oxide devices (ZnO/CuxO and NiO/CuxO) with low-cost and reliable electrochemical synthesis techniques. In the present study, we systematically investigated the RS properties of monolayer (CuxO, ZnO, and NiO) and bilayer (ZnO/CuxO and NiO/CuxO) devices. We observed that bilayer-switching devices show good RS properties as compared to monolayer devices. In particular, the ZnO/CuxO bilayer RS device showed good nonvolatile memory properties while the NiO/CuxO RS device mimicked various synaptic learning properties. To get clarity on the RS mechanisms, we probed the electrochemical impedance spectroscopy (EIS) technique for both kinds of devices. The EIS study confirms the type-II and type I memristive effects present in the ZnO/CuxO and NiO/CuxO devices, respectively. We found that the electrodeposited bilayer-switching layer has potential in RS applications.