Switching mode and mechanism in binary oxide resistive random access memory using Ni electrode

Resistive-switching (RS) modes in different CMOS-compatible binary oxides have been shown to be governed by the interplay with the Ni top electrode. Unipolar RS and metallic low-resistance state in polycrystalline HfO₂ and ZrO₂ are distinct from the preferential bipolar RS and semiconductive low-resistance state in amorphous Al₂O₃ and SiO₂. Backside secondary ion mass spectrometry (SIMS) has shown the formation of Ni filaments in HfO₂, in contrast to the formation of oxygen-vacancy filaments in Al₂O₃. The differences have been explained by strong dependence of Ni migration on the oxide crystallinity. Additionally, the RS mode can be further tailored using bilayer structures. The oxide layer next to the Si bottom electrode and its tendency of forming Ni filaments play significant roles in unipolar RS in the bilayer structures, in support of the conical-shape Ni filament model where the connecting and rupture of filaments for unipolar RS occur at the smallest diameter near the bottom electrodes.