Enhancement in neuromorphic NbO2 memristive device switching at cryogenic temperatures

TL;DR

This study investigates NbO₂ memristive devices at cryogenic temperatures, showing enhanced switching behavior and increased threshold voltage, with implications for improving device performance by reducing leakage current.

Contribution

The paper demonstrates that NbO₂ memristive devices exhibit improved switching characteristics at cryogenic temperatures, highlighting the role of temperature in device performance enhancement.

Findings

Threshold voltage increases by over 3 times at cryogenic temperatures.

Hold voltage remains below threshold voltage during fast voltage sweeps.

Lower activation energy (~1.4 eV) compared to other NbO₂ devices.

Abstract

The electrical properties and performance characteristics of niobium dioxide (NbO$_\mathrm{2}$)-based memristive devices are examined at cryogenic temperatures. Sub-stoichiometric Nb$_\mathrm{2}$O$_\mathrm{5}$ was deposited via magnetron sputtering and patterned in microscale (2$\times$2 - 15$\times$15 $\mu$m$^2$) cross-bar Au/Ru/NbO$_\mathrm{x}$/Pt devices and electroformed at 3-5 V to make NbO$_\mathrm{2}$ filaments. At cryogenic temperatures, the threshold voltage ($V_\mathrm{th}$) increased by more than a factor of 3. The hold voltage ($V_\mathrm{h}$) 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 non-volatile Nb$_\mathrm{2}$O$_\mathrm{5}$ in the filament. The devices have an activation energy of $E_a \approx 1.4$ eV, lower than other NbO$_\mathrm{2}$ devices reported. Our works shows that even nominally ``bad" memristive devices can be improved by reducing the leakage current and increases the sample resistance at cryogenic temperatures.