Local Ion Irradiation-Induced Resistive Threshold and Memory Switching in Nb₂O₅/NbO_<i>x</i> Films

Abstract

Resistive switching devices with a Nb₂O₅/NbO_<i>x</i> 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 NbO_<i>x</i> 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