Room temperature fabricated NbOx/Nb2O5 memory switching device with threshold switching effect

In this work, we present for the first time the coexistence of memory and threshold switching in a room temperature fabricated niobium oxide single layer, sandwiched in between metallic electrodes. The threshold switching effect, originating from substoichiometric NbO_x, increases the on/off resistance ratio between selected and unselected cells in a cross bar arrangement by a factor of 10. We disclose that an inevitable oxygen gradient can be induced in the active layer either by designed deposition of amorphous Nb₂O₅ and NbO_x using reactive dc magnetron sputtering or by the adoption of reactive Al top electrodes. The bottom electrode was always made from Pt. In 6 nm thin Nb₂O₅ layer with aluminum as reactive top electrode, bipolar resistive switching was verified in the voltage range of ± 1V. In contrast, no bipolar switching was observed if an inert platinum electrode was used. Purposeful sputter deposition with an oxygen gradient between Nb₂O₅ and Pt restored the bipolar switching characteristics of the device.