Negative differential resistance effect and dual bipolar resistive switching properties in a transparent Ce-based devices with opposite forming polarity

In this work, we have fabricated a transparent Ce-based device with aluminum-zinc oxide (AZO) as semiconducting electrode by radio-frequency (RF) sputtering on a transparent ITO/glass substrate at room temperature (RT). The device transmittance in the visible region of 400 to 800 nm was measured to be ~92%. Studies on the AZO/CeO₂/ITO/glass device reveal a dual-mode bipolar resistive switching (RS) behavior. Transparent device is found to exhibit both positive-set/negative-reset and negative-set/positive-reset switching modes with very good repetitiveness in cycle-to-cycle (C2C) switching, excellent DC endurance (>10³ cycles) and long retention (>10⁴ s). In addition, negative differential resistance (NDR) was noted to arise during positive electroforming and set-processes, and its physical origin was explored. The physics behind the NDR and dual bipolar RS behaviors were explained by the rise and fall in the density of oxygen vacancies in the CeO₂ layer, as was analyzed via x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) techniques. We believe that Ce-based transparent device presented in this work can offer robust passivation for electronic devices.