Nonpercolative metal-insulator transition in VO₂ single crystals

Detailed temperature-dependent transport, optical microscopy, and synchrotron-based polychromatic x-ray microdiffraction measurements have been carried out in the vicinity of the metal-insulator transition (MIT) temperature of VO₂ single crystals. The formation and propagation of a real-space phase boundary along the rutile c axis is monitored during the transition. Pure metallic rutile R, as well as insulating monoclinic M1 phases, is observed at the onset of MIT. The two phases are separated by a sharp-phase boundary. Our findings suggest a nonpercolative nature of the MIT in VO_2.