Hierarchical carbon nanostructure design: ultra-long carbon nanofibers decorated withcarbon nanotubes

Abstract

Hierarchical carbon nanostructures based on ultra-long carbon nanofibers (CNF)decorated with carbon nanotubes (CNT) have been prepared using plasma processes.The nickel/carbon composite nanofibers, used as a support for the growth ofCNT, were deposited on nanopatterned silicon substrate by a hybrid plasmaprocess, combining magnetron sputtering and plasma-enhanced chemical vapordeposition (PECVD). Transmission electron microscopy revealed the presence ofspherical nanoparticles randomly dispersed within the carbon nanofibers. The nickelnanoparticles have been used as a catalyst to initiate the growth of CNT by PECVD at600 °C. After the growth of CNT onto the ultra-long CNF, SEM imaging revealed the formationof hierarchical carbon nanostructures which consist of CNF sheathed with CNTs.Furthermore, we demonstrate that reducing the growth temperature of CNT to less than500 °C leads to the formation of carbon nanowalls on the CNF instead of CNT. This simplefabrication method allows an easy preparation of hierarchical carbon nanostructures over alarge surface area, as well as a simple manipulation of such material in order to integrate itinto nanodevices.