Formation of carbon nanofibers from decacyclene by ion beam irradiation

Amorphous carbon nanofibers with lengths of 1-20 μm, uniform diameters of 20-100 nm were generated by ion beam-irradiation of decacyclene whiskers that were prepared on a flat plate of any material during vapor-deposition of decacyclene, a polycyclic aromatic compound, in vacuum for only a few minutes. The length of the whiskers did not depend on the duration of the vapor-deposition, whereas the number density of the whiskers increased with increasing the duration and reached 6.9 × 107 cm−2 at 4.5 min after starting the vapor-deposition. Irradiation of more than 1016 ions/cm2 with a 200 keV N+ ion beam converted the whiskers to carbon nanofibers with the electrical conductivity comparable to that of graphite. This novel method of preparation is advantageous for aligning the fibers on a desired location, since the fibers are generated only on the irradiated part at ambient temperature without catalyst.