Reduced Threshold Current in NbO₂ Selector by Engineering Device Structure

The leakage current scaling issues for NbO 2 selector devices are investigated. By introducing a rough Pt bottom electrode (BE) (RMS roughness ~2.5 nm) and inserting a 20-nm-thick dielectric layer (Nb 2 O 5 and HfO 2 ) between the BE and NbO 2 layer, we show that the threshold current for the insulator-metal-transition in microscale devices (~150 μm) can be reduced to ~20 μA, close to that realized in nanoscale (~10 nm) 3-D vertical ReRAM. This could be attributed to a thermal confinement effect caused by the presence of a permanent conductive filament in dielectric layer. The experimental results are supported by finite element simulation.