Microspectroscopic detection of local conducting areas generated by electric-pulse-induced phase transition in VO2 films

Insulator-metal phase transitions were induced in VO2/Al2O3 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 VO2 film, the multilevel switching was directly related to the formation of local conducting paths, which originated from sample inhomogeneity. (c) 2007 American Institute of Physics.