Threshold switching polycrystalline NbO2: Decay and recovery of the on state at room and low temperatures and its relationship to trapping centers

Double pulse switching experiments, performed on polycrystalline NbO2 at 300 and 15 K, reveal properties strongly associated with electronic, nonthermal, threshold switching. The data indicate a trapped carrier lifetime of 200 ns, agreeing with our previous measurements on polycrystalline NbO2 devices (data that had been obtained by a different method). The study also shows the functional increase of on-state lifetime with increasing overvoltage and the effect of overvoltage on the on-state I-V characteristics during fast polarity reversal. These results, coupled to previous work, are explicable in terms of a trap-limited transition to a metal-like state induced by a critical electric field and carrier concentration.