Ultra-long, free-standing, single-crystalline vanadium dioxide micro/nanowires grown by simple thermal evaporation

Recently, it was discovered that single-crystalline VO2 nanostructures exhibit unique, single-domain metal-insulator phase transition. They enable a wide range of device applications as well as discoveries of oxide physics beyond those can be achieved with VO2 bulk or thin films. Previous syntheses of these nanostructures are limited in density, aspect ratio, single-crystallinity, or by substrate clamping. Here we break these limitations and synthesize ultra-long, ultra-dense, and free-standing VO2 micro/nanowires using a simple vapor transport method. These are achieved by enhancing the VO2 nucleation and growth rates using rough-surface quartz as the substrate and V2O5 powder as the evaporation source.