Effect of Pt top electrode deposition on the valence state and resistance switching behavior of NbO_2-x

Resistive random-access memory (ReRAM) devices for cross-point array structures require selector elements to suppress the sneak current though neighboring cells. Niobium oxide is a promising candidate for one selector-one ReRAM (1S1R) device because of its diverse electrical characteristics such as resistance threshold switching in NbO₂ and resistance memory switching in Nb₂O₅. In this study, a new method to fabricate a self-formed 1S1R device is suggested, which uses the top electrode Pt sputtering process. During the Pt sputtering of the top electrode, it was observed that the Nb⁴⁺ in NbO_2-x layer was oxidized into Nb⁵⁺, resulting in Nb₂O₅-rich films. Such self-formed Nb₂O₅/NbO_2-x layer exhibits dissimilar resistance switching behaviors depending on the compliance current during memory operation. A switching model is proposed based on the resistance switching characteristics of the Nb₂O₅/NbO_2-x layer on the compliance current during memory operation.