Exploring the Bifunctionality of YSZ Thin Films in MOS Structures: Bridging the Gap between RRAM and Super-Pseudocapacitor Technologies

This investigation explores the resistive switching and energy storage capabilities of 100 nm yttria-stabilized zirconia (YSZ) thin films in a metal-oxide-semiconductor (MOS) configuration. Under soft voltage and temperature conditions, the device primarily functions as a conventional MOS capacitor with excellent insulating properties. However, upon exceeding a voltage threshold of 10.5 V, the resistive switching mechanisms are triggered. The multilevel memory properties of the device were investigated by employing triangular-shaped voltage pulses. The results showed excellent control of the resistance states through the intensity of the applied voltage. Furthermore, state retention experiments revealed a transition from short- to long-term data storage properties, holding promising characteristics for the development of neuromorphic materials. To gain a deeper understanding of the internal mechanisms in YSZ thin films, a combination of chronoamperometric and impedance spectroscopy analyses were performed. Through these results, we found that the induction of resistive switching mechanisms correlates with an increase in permittivity. This characteristic distinguishes them from traditional devices, where the capacitive properties typically decrease after the switching process. Additionally, we investigate the influence of temperature on the energy storage functionality of the device. Remarkably, as the temperature rises from 25 to 60 °C, the electrical response of the films resembles that of a supercapacitor. Furthermore, electrode/electrolyte reactions occur at temperatures from 60 to 100 °C, resulting in a pseudocapacitive performance comparable to commercial batteries in terms of energy and power densities.