Mechanistic study of cobalt catalyzed growth of carbon nanofibers in a confined space by plasma-assisted chemical vapor deposition

Carbon nanofibers (CNFs) were grown in the porous anodic aluminum oxide (AAO) thin film grown on the Si wafer by electron cyclotron resonance chemical vapor deposition using cobalt as the catalyst. A larger Co particle electrodeposited in the AAO pore channel produced vertically aligned CNFs with a tube diameter in compliance with the pore size of the AAO template. On the other hand, a smaller Co particle resulted in CNF growth with a nonuniform distribution of the tube diameter and a sparse tube density. Amorphous carbon residue produced under the plasma-assisted CNF growth condition seemed to play an essential role leading to the observation. A growth mechanism is proposed to delineate the volume effect of the electrodeposited Co catalyst on the CNF growth confined in pore channels of the AAO template.