Surface oriented self-assembly of carbon nanotubes

In this paper, we demonstrate the self assembled growth of nanotubes along the surface of (100), (110) and (111) silicon wafers using thermal CVD. Iron nanoparticles, 10 nm in diameter, were used as the catalyst. Carbon nanotubes were grown in a methane atmosphere at 1000degreesC. SEM and AFM characterization revealed single wall carbon nanotubes, about 10 nm in diameter and up to 10 mum in length, growing along the <111> direction of the silicon wafer. The mechanism of growth of nanotubes is similar to that of molecular epitaxy which occurs due to the lattice matching of the silicon and iron crystal lattices forming self aligned silicides at high temperature which help orient the nanotubes. This process may enable the integration of nanotubes with CMOS processing technology.