Pulsed laser CVD investigations of single-wall carbon nanotube growth dynamics

The nucleation and rapid growth of single-wall carbon nanotubes (SWNTs) were explored by pulsed-laser assisted chemical vapor deposition (PLA-CVD). A special high-power, Nd:YAG laser system with tunable pulse width (> 0.5 ms) was implemented to rapidly heat (> 3 x 10(4)degrees C/s) metal catalyst-covered substrates to different growth temperatures for very brief (sub-second) and controlled time periods as measured by in situ optical pyrometry. Utilizing growth directly on transmission electron microscopy grids, exclusively SWNTs were found to grow under rapid heating conditions, with a minimum nucleation time of > 0.1 s. By measuring the length of nanotubes grown by single laser pulses, extremely fast growth rates (up to 100 microns/s) were found to result from the rapid heating and cooling induced by the laser treatment. Subsequent laser pulses were found not to incrementally continue the growth of these nanotubes, but instead activate previously inactive catalyst nanoparticles to grow new nanotubes. Localized growth of nanotubes with variable density was demonstrated through this process and was applied for the reliable direct-write synthesis of SWNTs onto pre-patterned, catalyst-covered metal electrodes for the synthesis of SWNT field-effect transistors.