Morphological transition of vertically aligned one-dimensional zinc oxide

Vertically aligned 1D ZnO nanostructures have been synthesized on Si (100) substrates by thermal evaporation of zinc oxide powders without using a catalyst. The morphology and size of the as-grown ZnO nanorods gradually change as the distance between the substrate and the source increases. All of the nanorods are synthesized not on the Si substrate, but on the ZnO buffer layer, which forms on Si substrate during the growth process. The as-grown ZnO nanostructures show a morphological transition from nanorods with an abrupt tip to nanorods with a blunt tip, to nanonails with a cap, and finally to ZnO quantum dots as the temperature of the Si substrate decreases.