2005 年 20 巻 2 号 p. 108-115
Monodisperse metal nanoparticles have been used as a catalyst for growing carbon nanotubes (CNTs). The nanoparticles were generated by laser ablation and size-classified with a differential mobility analyzer at low pressures (1-1.5 kPa). CNTs were grown by hot filament or thermal chemical vapor deposition at temperatures of 510-610 °C using acetylene. First, multi-walled carbon nanotubes (MWNTs) were grown from 5-nm nickel particles on a silicon substrate. The MWNTs had outer diameters matching the particle sizes, indicating that the current method can produce diameter-controlled MWNTs. Secondly, for applications of CNTs to LSI interconnects, 5-nm cobalt particles were injected into via holes of LSI interconnects by utilizing a directed particle beam. The directed particle beam was produced by introducing the particles into a high vacuum chamber using differential pumping. The particles were deposited at the bottom of the holes with a diameter as small as 100 nm. Aligned MWNTs were successfully grown in the holes. Finally, titanium-cobalt bimetallic particles were used to grow MWNTs to study the effects of titanium on the growth. It was found that titanium enhances the MWNT growth significantly. There is an optimum titanium fraction for the growth, as confirmed by evaluating the growth probabilities of MWNTs.