Evidence of field-induced nucleation switching in opal: VO2 composites and VO2 films

We show that electrical switching in opal-VO2 composites is governed by the electric field rather than voltage or current. This makes it similar to switching in chalcogenide glasses with the underlying mechanism identified as the field induced nucleation. However, the observed bias dependence of switching delay time is found to be noticeably different from that of standard VO2 films on "smooth" substrates. This difference is attributed to the disorder effects in polycrystalline structures. The model of field induced nucleation is shown to apply when properly modified to account for that disorder.