Vacancy-modulated self-rectifying characteristics of NiO_x/Al₂O₃-based nanoscale ReRAM devices

A vacancy-modulated self-rectifying resistive random access memory (ReRAM) with a Ti/NiO_x/Al₂O₃/Pt structure is proposed in this study. Here, NiO_x is used as a resistive switching layer, and Al₂O₃ is used as a tunnel barrier layer for producing self-rectifying behavior. The tunnel barrier thickness in the NiO_x/Al₂O₃ interfacial region can be increased or decreased according to the movement of oxygen vacancies in the NiO_x layer under positive or negative voltages, respectively, thereby leading to self-rectifying resistive switching behavior. As a result, the NiO_x/Al₂O₃-based self-rectifying ReRAM exhibits a low operation current of ∼3 × 10⁻⁷ A, large ON/OFF ratio of ∼6 × 10³, high rectification ratio of ∼5 × 10², long retention of 10⁵ s, and forming-free and self-compliance characteristics, meeting the next generation ReRAM requirements. The Ti/NiO_x/Al₂O₃/Pt-based self-rectifying structures can pave the way to develop high-density embedded memory applications in the future.