Semiconductor CdS hierarchical nanostructures have been fabricated through thermal evaporation with a mixture of CdS nanopowders, SnO2 nanopowders, and graphite powders. Sri nanoparticles are located at or close to the tips of the nanowires and the growth branches served as the catalyst for the growth of a vapor-liquid-solid mechanism. The morphology and microstructure of CdS axial nanowires and branches were measured by scanning electron microscopy and high-resolution transmission electron microscopy. The long and straight central axial CdS nanowires grow along the [0001] direction. Branched CdS nanoneedles are vertically aligned over the surface of the CdS axial nanowire in the radial direction. The hierarchical nanostructures could be a candidate for building ultrahigh sensitivity sensors due to the unique structure. (c) 2006 Elsevier B.V. All rights reserved.