Diode-less bilayer oxide (WOx-NbOx) device for cross-point resistive memory applications

The combination of a threshold switching device and a resistive switching (RS) device was proposed to suppress the undesired sneak current for the integration of bipolar RS cells in a cross-point array type memory. A simulation for this hybrid-type device shows that the matching of key parameters between switch element and memory element is an important issue. Based on the threshold switching oxides, a conceptual structure with a simple metal-oxide 1-oxide 2-metal stack was provided to accommodate the evolution trend. We show that electroformed W-NbOx-Pt devices can simultaneously exhibit both threshold switching and memory switching. A qualitative model was suggested to elucidate the unique properties in a W-NbOx-Pt stack, where threshold switching is associated with a localized metal-insulator transition in the NbOx bulk, and the bipolar RS derives from a redox at the tip of the localized filament at the WOx-NbOx interface. Such a simple metal-oxide-metal structure, with functionally separated bulk and interface effects, provides a fabrication advantage for future high-density cross-point memory devices.