Incremental Growth of Single-Wall Carbon Nanotube Arrays Explored by Pulsed CVD

Gas pulses of variable duration and peak flux were used to explore the incremental growth and evolution of alignment of vertically-aligned carbon nanotubes arrays (VANTAs) by typical chemical vapor deposition within a tube furnace. Time-resolved reflectivity from Fe/Al catalyst-coated Si substrates was used to follow the growth of the arrays after the arrival of successive acetylene gas pulses injected into fast argon-hydrogen flows at 6 Torr total pressure. The evolution of alignment of the arrays measured with the in situ optical reflectivity data was correlated with SEM images for growth resulting from single- and multiple-pulse growth. The incremental length per pulse was varied from 20 nm to several microns in less than a second, corresponding to growth rates ranging up to 7 microns/second. Effects of repeated renucleation of growth along the nanotube wall structure were measured by HRTEM and Raman spectroscopy.