Voltage-triggered insulator-to-metal transition of ALD NbOx thin films for a two-terminal threshold switch†
We report two-terminal threshold devices that use niobium oxide (NbOx) thin films that were synthesized using atomic layer deposition (ALD) then pulsed-laser annealing. The ALD growth conditions for NbOx thin films were optimized using niobium(V) ethoxide and deionized water at 170 °C. As-deposited NbOx films were amorphous with Nb5+ valence state, but laser annealing led to partial conversion to NbO2 crystallites with Nb4+ valence states. This two-terminal device with ALD-NbOx exhibits excellent threshold switching with low off current ∼847 nA at 1 V, high on/off current ratio (∼103), high reliability, fast switching time (<20 ns) and high modulation frequency (>1 MHz).