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 NbOx, 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 NbOx 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.