Multistep metal insulator transition in VO2 nanowires on Al2O3 (0001) substrates

We observed a temperature- and voltage-induced multistep metal-insulator transition (MIT) in vanadium dioxide nanowires fabricated on Al2O3 (0001) substrates. Nanowires with a width of 200 nm showed a multistep MIT that exhibited a resistivity change of nearly two orders of magnitude in a 0.5 K temperature step. These multistep resistivity jumps can be understood as a transition of a single domain, whose size is estimated to be around 50–70 nm from numerical calculation. We found that the temperature-induced isotropic conductive behavior of the nanowires becomes similar to the voltage-induced anisotropic one as their width decreases.