Role of tantalum nitride as active top electrode in electroforming-free bipolar resistive switching behavior of cerium oxide-based memory cells

Electroforming-free cerium oxide-based bipolar resistive switching memory devices have been deposited using radio frequency magnetron sputtering technique. These devices demonstrate two types of forming-free cells: some in the low-resistance state and the others in high-resistance state. The transmission electron microscopy and X-ray diffraction analyses illustrate the formation of tantalum oxynitride layer between tantalum nitride (TaN) and cerium oxide (CeO_x), which looks to be responsible for the two types of cells as well as their memory performance. Ohmic and Poole-Frenkel conductionmechanisms are found to be responsible for charge transport in the low-and high-resistance states. The current-voltage characteristics and temperature dependence of resistance suggest that resistive switching mechanism in our TaN/CeO_x/Pt devices may be explained by the model of connection and disconnection of filamentary paths made of oxygen vacancies. The reliability characteristics of TaN/CeO_x/Pt devices indicate better endurance and stable retention performance at relatively lower programming voltages and larger memory window (OFF/ON resistance ratio ∼10³) at room temperature and at 100 °C.