Unipolar Resistive Switching Characteristics of a $\hbox {ZrO}_{2}$ Memory Device With Oxygen Ion Conductor Buffer Layer

Oxygen ion migration is an important factor in the formation and rupture of a conducting filament to cause resistive switching (RS) behavior. A calcium oxide-doped zirconium oxide (CaO:ZrO₂) oxygen ion conductor buffer layer is introduced between the Ti/ZrO₂ interface of conventional Ti/ZrO₂/Pt memory devices to improve their unipolar RS properties. Increasing the CaO doping concentration to 2 mol% introduces higher oxygen vacancy content within the CaO:ZrO₂ buffer layer, leading to higher oxygen ion conductivity. This allows more oxygen ions to migrate from the oxygen reservoir laterally and vertically across the 2-mol% CaO:ZrO₂ buffer layer to the region where the conducting filament forms and ruptures. Therefore, the Ti/2-mol% CaO:ZrO₂/ZrO₂/Pt device in this letter exhibits good endurance, high-speed switching (50 ns) without soft errors, stubborn nondestructive readout, and stable retention at 150°C.