Two step floating catalyst chemical vapor deposition including in situ fabrication of catalyst nanoparticles and carbon nanotube forest growth with low impurity level

Abstract

Carbon nanotube (CNT) forest with very low concentration of metallic impurity particle was grown by a two-step floating-catalyst chemical vapor deposition (CVD) method. Fe catalyst nanoparticles were uniformly formed on the substrate by flowing ferrocene/ethanol mist generated by an ultrasonic nebulizer. Then, the growth of the CNT forest was followed by a thermal CVD process in an identical furnace with acetylene as a carbon source. The separated process of catalyst formation and CNT growth leads to no formation of impurity particles on the CNT surfaces with a lower impurity level of 0.8 wt%. The gas-phase flow of the catalyst solution enables precise control of catalyst formation including diameter, radius of curvature and areal density of catalyst particle for long and dense CNT forest. The CNT forest grown under optimum conditions had a spin capability because of its high areal density greater than 1 × 1011 cm−2.