Formation of loops on the surface of carbon nanofibers synthesized by plasma-enhanced chemical vapor deposition using an inductively coupled plasma reactor

Carbon nanofibers (CNFs) were synthesized by both high-density plasma-enhanced chemical vapor deposition (CVD) and thermal CVD. The growth in the former was carried out in an inductively coupled plasma (ICP) reactor. The multilayer loop structure, which was reported to be found on both the inner and outer surfaces of cup-stacked-type CNFs grown using thermal CVD only after heat treatment above 1500 °C, was observed in the as-grown CNFs only on the outer surface using ICP-CVD. The dangling bonds caused by plasma etching and the bonding between edge carbon atoms aided by the high-density plasma are considered the main reasons of the formation of multilayer loops.