Enhancement in neuromorphic NbO2 threshold switching at cryogenic temperatures.

The electrical properties and performance characteristics of niobium dioxide (NbO 2)-based threshold switching devices are examined at cryogenic temperatures. Substoichiometric Nb 2 O 5 was deposited via magnetron sputtering and patterned in microscale (2 × 2 − 15 × 15 μ m 2) crossbar Au/Ru/NbO x /Pt devices and electroformed at 3–5 V to make NbO 2 filaments. At cryogenic temperatures, the threshold voltage (V th ) increased by more than a factor of 3. The hold voltage (V h ) was significantly lower than the threshold voltage for fast voltage sweeps (200 ms per measurement). If the sample is allowed to cool between voltage measurements, the hold voltage increases, but never reaches the threshold voltage, indicating the presence of nonvolatile Nb 2 O 5 in the filament. The devices have an activation energy of E a ≈ 1.4 eV, lower than other NbO 2 devices reported. Our work shows that even nominally "bad" selector devices can be improved by reducing the leakage current and increasing the sample resistance at cryogenic temperatures. [ABSTRACT FROM AUTHOR]