Effect of the On/Off Cyclic Modulation Time Ratio of C₂H₂/H₂ Flow on the Low Temperature Deposition of Carbon Nanofilaments

Low temperature (less than 600 °C) deposition of carbon nanofilaments (CNFs) could be achieved on the silicon oxide substrate by thermal chemical vapor deposition system. We used Fe(CO)₅ as the catalyst precursor for CNFs formation. For the enhancement of CNFs formation density, the source gas flow was intentionally manipulated as the cyclic on/off modulation of C₂H₂/H₂ flow during the initial deposition stage. The CNFs formation density on silicon oxide substrate could be much enhanced by the cyclic modulation process having the higher growing/etching time ratio (180/30 s). Furthermore, the lattice structures of CNFs developed into carbon nanotubes at the higher growing/etching time ratio (180/30 s) case. The solely hydrogen gas feeding (C₂H₂ flow off) time during the initial deposition stage seems to play an important role for the variation in the CNFs formation characteristics by the cyclic modulation process.