Role of annealing temperature on the sol-gel synthesis of VO nanowires with characterization of their metal-insulator transition.

Among the techniques to create VO nanostructures, the sol-gel method is the most facile and benefits from simple, manipulable synthetic parameters. Here, by utilizing various TEM techniques, we report the sequential morphological evolution of VO nanostructures in a sol-gel film spin-coated on a customized TEM grid, which underwent oxygen reduction as the annealing temperature increased. TEM dark-field imaging and Raman spectroscopy allowed us to confirm the sharp phase transition behavior of an individual nanowire by illustrating the effect of electrode-clamping-induced tensile stress on the nucleation of the R phase from the M1 phase. The electrical transport properties of a single-nanowire device fabricated on a customized TEM grid showed excellent control of the stoichiometry and crystallinity of the wire. These results offer critical information for preparing tailored VO nanostructures with advanced transition properties by the sol-gel method to enable the fabrication of scalable flexible devices.