Comparing micro- and nanoscale NbO2 devices for memristive applications*

Thin-film NbO2 is an attractive material as a memristor in neuromorphic computing due to its lost cost, low toxicity, and excellent switching behavior.  In this talk we compare the switching behavior of annealed nanoscale ($50 imes 50$ - $170 imes 170$ nm$^2$) devices and electroformed microscale ($2 imes 2$ - $20 imes 20$ $mu$m$^2$) cross-bar devices.  We show that electroformed devices using the microscale cross-bar pattern are uniform size filaments, have poor switching behavior, and are not good candidates for memristors.  In contrast, nanoscale devices annealed at 700 $^circ$C show bulk crystallization with resistances that scale with inverse area, $RsimA^{-1}$, and the nanoscale devices have excellent switching behavior, with differences between the threshold and hold voltages of more than 1 V ($V_{th} – V_h > 1$ V).  This indicates that annealed nanoscale devices are better candidates for memristors than the more common electroformed microscale cross-bar devices.