Nanodiamond-coated carbon nanotubes: Early stage of the CVD growth process

A series of deposits formed by single-walled carbon nanotube (SWNT) bundles coated by nanocrystalline diamond (NCD) are produced using a modified CVD reactor. The nanocylindrical structures are deposited on Si substrates using carbon nanopowders and atomic H as reactants. The nanocrystalline coating obtained from short-time runs lasting up to 6 min are analyzed by micro-Raman and cathodoluminescence (CL) techniques, in order to obtain information on the structural evolution of the material during the first steps of the growth process. The morphological investigation performed by field emission scanning electron microscopy (FESEM) indicates that the nanocrystalline coating generated by a process lasting 46 min is formed by protruding embryo diamond crystallites with a needle-like shape. Thereafter the shape of the diamond phase evolves giving rise to elongated and better faceted diamond grains'well anchored on the nanotube bundle surfaces.