Morphology of the as-grown CNWs displayed in the SEM images. (a) An SEM image of CNWs on a silicon substrate; primary beam incident kinetic energy was 30 keV. (b) CNWs uniformly distributed on the substrate over approximately 1 cm2. (c-e) The CNWs were quasi-transparent to the SEM electron beam. (f) The cluster of CNWs is "flower-like".