This paper investigates the origin of the threshold switching effect in niobium oxide based filamentary switching cells.

Resistive switching devices with a Nb2O5/NbOx bilayer stack combine threshold and memory switching. Here we present a new fabrication method to form such devices. Amorphous Nb2O5 layers were treated by a krypton irradiation. Two effects are found to turn the oxide partly into a metallic NbOx layer: preferential sputtering and interface mixing. Both effects take place at different locations in the material stack of the device; preferential sputtering affects the surface, while interface mixing appears at the bottom electrode. To separate both effects, devices were irradiated at different energies (4, 10, and 35 keV). Structural changes caused by ion irradiation are studied in detail. After successful electroforming, the devices exhibit the desired threshold switching. In addition, the choice of the current compliance defines whether a memory effect adds to the device. Findings from electrical characterization disclose a model of the layer modification during irradiation.

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Resistive switching effects in metal-insulator-metal (MIM) structures are strongly influenced by the electrode materials. In this work a platinum-free symmetric Al/Nb 2 O 5 /Al device is compared to a device with platinum bottom electrode. For the device with the platinum bottom electrode, filamentary based resistive switching with good data retention was observed up to 125 °C. For the Al/Nb 2 O 5 /Al device, an area dependent pure electronic based resistive switching was observed. Electron trapping at the bottom electrode interface is responsible for the observed analog switching behavior which makes an Al/Nb 2 O 5 /Al device suitable for neuromorphic applications.

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