2.3.1 Arc-Discharge and Laser Ablation

Arc-discharge and laser ablation methods for the growth of CNTs have been actively pursued in the past decades. Both methods involve the condensation of carbon atoms generated from evaporation of solid carbon sources. The temperature involved in these methods are $ 3000-4000$° C, close to the melting temperature of graphite.

In arc-discharge, carbon atoms are evaporated by a helium plasma initiated by high currents passed through an opposing carbon anode and cathode. Arc-discharge has been developed into an excellent method for producing both high quality MW-CNTs and SW-CNTs. For the growth of SW-CNTs, a metal catalyst is needed in the arc-discharge system. The first success in producing substantial amount of SW-CNTs by arc-discharge was achieved by BETHUNE and coworkers in 1993 [23], by using a carbon anode containing a small percentage of cobalt in the discharge experiment.

The growth of high quality SW-CNTs was achieved by SMALLEY and coworkers using a laser ablation method [24]. The method utilized intense laser pulses to ablate a carbon target containing 0.5 atomic percent of nickel and cobalt. The target was placed in a tube-furnace heated to 1200°C.

In SW-CNT growth by arc-discharge and laser ablation, typical by-products include fullerene, graphitic polyhedrons with enclosed metal particles, and amorphous carbon in the form of particles or over-coating on the CNT sidewalls.

M. Pourfath: Numerical Study of Quantum Transport in Carbon Nanotube-Based Transistors