Increased Yield and Uniformity of Vanadium Dioxide Nanobeam Growth via Two-Step Physical Vapor Transport Process

Single-crystal vanadium dioxide (VO2) nanobeams are attractive materials to investigate the influence of dimensions on the metal-insulator transition, so simple strategies to control yield and morphology are desirable. In a physical vapor transport process, three distinctive morphologies of VO2 nanostructures, nanoparticles, nanowires, and nanosheets, were observed depending on local source supersaturation and temperature. On the basis of these observations, a practical two-step synthetic approach was devised to modify the supersaturation during growth, separately optimizing nucleation density and nanobeam aspect ratio. Increased yield and uniformity in length associated with simultaneous nucleation could be achieved with modulation of oxygen flow or seeding the substrate with nuclei. The ability to lower the supersaturation while maintaining high densities of nanobeams also improved control over the morphology.