Diamond Nanocrystals Growth on Carbon Nanotubes

Aiming at the growth of diamond nanowires on carbon nanotubes we have studied carbon nanotubes for treatment in pure hydrogen in Hot‐Filament assisted chemical vapour deposition reactor (HFCVD). Purified multiwalled carbon nanotubes were dispersed onto silicon substrates, and annealed in pure hydrogen in HFCVD reactor. Important parameters were substrate temperature (650 to 870° C), nanotube density, annealing time (1 to 4 hours), hot‐filament temperature (HFVCD, 1900 to 2350° C), and gas pressure (30 to 70 Torr). No catalyst was used, and no methane was introduced in the chamber. Annealed samples were studied by Field Emission SEM and EDX analysis. Results show that for a filament temperature of 2000 to 2350° C, carbon nanotubes are rather stable in atomic hydrogen environment. For higher filament temperatures (>2350° C) nanotubes are converted into microcrystalline graphite, and for lower temperatures (1900–1950° C) nanotubes are etched away. In the conditions in which nanotubes are stable, growth of nano‐objects were observed on the surface of nanotubes, in particular nanocrystals (3 to 5 nm in diameter). In some cases growth of nanowires (5 to 10 nm in diameter and 100 to 200 nm in length) was also observed.