The structure and growth mechanism of VO2 nanowires

Single crystalline VO2 nanowires grown on the surface of amorphous silica showed interesting growth behaviors. Due to the strong affinity between the vanadium oxide nanocrystals and silica surfaces, all VO2 nanowires grew along the substrate surface without the aid of any catalysts. The growth of VO2 nanowires was interpreted by the oxide-assisted growth mechanism based on the study of the special nanowire tip structures. Because the vanadium oxides at the growth tip and the nanowire body had different melting temperatures, and VO2 crystals had a very different thermal expansion coefficient in comparison with silica, the growth tips separated from the nanowires during cooling of the substrate. Under the electron-beam irradiation, the reversible phase transition between the monoclinic and tetragonal structures in VO2 nanowires was investigated at atomic level by high-resolution transition electron microscopy.