Regrowth of carbon nanotube array by microwave plasma-enhanced thermal chemical vapor deposition

A repeated growth process (regrowth process) has been carried out to fabricate a carbon nanotube (CNT) array without additional catalyst by a custom-made plasma-enhanced thermal chemical vapor deposition (PE-thermal CVD) technique. An Fe film with a thickness of 3 nm is coated as a catalyst before the first growth on the SiO(2)/Si by arc plasma deposition. Two types of treatments, lift-off and thermal annealing, are used to remove the CNTs away for the next growth. Thermal annealing is also used to remove amorphous carbon, which covers the catalytic nanoparticles and to activate the catalyst. The CNT array is regrown without coating additional catalyst through the regrowth process. After certain cycles, high-purity single-walled carbon nanotubes (SWNTs) are synthesized and the I(D)/I(G) ratio of the Raman spectrum reaches a low value of 0.41. The crystallization of CNTs is improved after each growth cycle of thermal annealing treatment.