Self-catalysed growth of zinc oxide nanowires

Single-crystal nanowires of zinc oxide were prepared by a novel self-seeded vapour-liquid-solid (VLS) growth method using ultrasonic spray-assisted chemical vapour deposition, in which liquid Zn droplets were used as,catalysts'. In this approach, a nanocrystalline seed layer was first deposited, by direct decomposition of a zinc acetate precursor solution, onto a glass substrate at a temperature slightly below the melting point (420 degrees C) of Zn. ZnO nanowires were subsequently grown at a temperature above the melting point of Zn. From transmission electron microscopy, solidified Zn/ZnO droplets were observed on the ends of the ZnO nanowires. A novel mechanism for self-seeded growth of ZnO by the 'vapour (Zn acetate)-liquid (Zn)-solid (ZnO)' growth mechanism is described. The main advantage of the method is that it is clean, since growth occurs in the absence of a second phase catalyst.