Catalyst-free low-temperature growth of carbon nanofibers by microwave plasma-enhanced CVD

Abstract

Catalyst-free low-temperature growth of carbon nanofibers was performed by a microwave plasma-enhanced chemical vapor deposition using CO/Ar/O 2 system. At the optimum oxygen concentration of O 2/CO = 7/1000, vertically aligned CNFs can be synthesized at temperature as low as 180 °C without any catalyst materials, whose diameter is about 50–100 nm and growth rate is about 5 nm/s. It is concluded that the addition of a small amount of O 2 is the key for the synthesis of CNFs without catalyst, because it suppresses the isotropic deposition of amorphous carbon and assists the anisotropic linear growth of crystallized carbon deposits.