Stress-induced domain dynamics and phase transitions in epitaxially grown VO ₂ nanowires

We demonstrate that surface stresses in epitaxially grown VO ₂ nanowires (NWs) have a strong effect on the appearance and stability of intermediate insulating M ₂ phases, as well as the spatial distribution of insulating and metallic domains during structural phase transitions. During the transition from an insulating M ₁ phase to a metallic R phase, the coexistence of insulating M ₁ and M ₂ phases with the absence of a metallic R phase was observed at atmospheric pressure. In addition, we show that, for a VO ₂ NW without the presence of an epitaxial interface, surface stresses dominantly lead to spatially inhomogeneous phase transitions between insulating and metallic phases. In contrast, for a VO ₂ NW with the presence of an epitaxial interface, the strong epitaxial interface interaction leads to additional stresses resulting in uniformly alternating insulating and metallic domains along the NW length.