| Summary: | Resistive random-access memory (RRAM) devices are fabricated by utilizing silicon oxynitride (SiO<sub>x</sub>N<sub>y</sub>) thin film as a resistive switching layer. A SiO<sub>x</sub>N<sub>y</sub> layer is deposited on a p+-Si substrate and capped with a top electrode consisting of Au/Ni. The SiO<sub>x</sub>N<sub>y</sub>-based memory device demonstrates bipolar multilevel operation. It can switch interchangeably between all resistance states, including direct SET switching from a high-resistance state (HRS) to an intermediate-resistance state (IRS) or low-resistance state (LRS), direct RESET switching process from LRS to IRS or HRS, and SET/RESET switching from IRS to LRS or HRS by controlling the magnitude of the applied write voltage signal. The device also shows electroforming-free ternary nonvolatile resistive switching characteristics having R<sub>HRS</sub>/R<sub>IRS</sub> > 10, R<sub>IRS</sub>/R<sub>LRS</sub> > 5, R<sub>HRS</sub>/R<sub>LRS</sub> > 10<sup>3</sup>, and retention over 1.8 × 10<sup>4</sup> s. The resistive switching mechanism in the devices is found to be combinatory processes of hopping conduction by charge trapping/detrapping in the bulk SiO<sub>x</sub>N<sub>y</sub> layer and filamentary switching mode at the interface between the SiO<sub>x</sub>N<sub>y</sub> and Ni layers.
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