Microspectroscopic detection of local conducting areas generated by electric-pulse-induced phase transition in v O2 films

Insulator-metal phase transitions were induced in V O2 Al2 O3 films by applying a voltage pulse to a micrometric junction. We investigated the mechanism involved both spatially and temporally using midinfrared microspectroscopy. At the phase transition, we found that multilevel current switching occurred, a behavior typical of numerous compounds showing electric-pulse-induced resistance switching. We were able to demonstrate that in the case of our V O2 film, the multilevel switching was directly related to the formation of local conducting paths, which originated from sample inhomogeneity.