This paper reports an abnormal coexistence of different resistive switching behaviors including unipolar (URS), bipolar (BRS), and threshold switching (TRS) in an Al/NiO/indium tin oxide (ITO) structure fabricated by chemical solution deposition. The switching behaviors have been strongly dependent on compliance current (CC) and switching processes. It shows reproducible URS and BRS after electroforming with low and high CC of 1 and 3 mA, respectively, which is contrary to previous reports. Furthermore, in the case of high-forming CC, TRS is observed after several switching cycles with a low-switching CC. Analysis of current-voltage relationship demonstrates that Poole-Frenkel conduction controlled by localized traps should be responsible for the resistance switching. The unique behaviors can be dominated by Joule heating filament mechanism in the dual-oxygen reservoir structure composed of Al/NiO interfacial layer and ITO. The tunable switching properties can render it flexible for device applications.

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The n-ZnO/p-NiO junctions have been fabricated by sol-gel method using Al as top electrodes and ITO as bottom electrodes for applications in resistive switching devices. Such devices exhibit homogenous and filamentary characteristics depending on the amplitude of applied bias. The two switching types show different switching polarities and transport mechanisms. Under a higher bias, the filamentary behavior is dominated by Ohmic conduction at low resistance state and trap related Poole-Frenkel conduction at high resistance state, while under a lower bias the homogenous switching exhibits diode conduction at high resistance state and space charge limited current at low resistance state. The homogenous switching shows selfrectifying effect with a good endurance. It may open up a simple route to suppress the sneak current in a p-oxide/noxide device while maintaining reasonable good resistive switching and self-rectifying properties. Graphical AbstractKeywords Resistive random access memory • Resistive switching • Self-rectifying • n-ZnO/p-NiO

We investigated the bipolar resistive switching (BRS) properties of Mn-doped NiO thin films by sol–gel spin-coating.