Fig. 1.

Molecular O₂-assisted synthesis of high-yield V-SWNTs. (A) AFM image of a submonolayer of Fe nanoparticles (1–2 nm in topographic height) formed on a SiO₂/Si wafer used for the synthesis. (B) Optical image of a visually black vertical SWNT film grown on a full 4-inch wafer. The tube-free region at the lower right of the wafer was due to clamping during deposition of Fe film. (C) A SEM image showing the slanted view of a V-SWNT film grown on SiO₂/Si. (D) A SEM side view of a V-SWNT film. (E) Raman spectrum of a SWNT film. Laser excitation wavelength is 785 nm. (F) TEM image of SWNTs after they were sonicated off of the SiO₂ and then dispersed onto a TEM grid. Note that using excessive O₂ (>≈2%, below the ignition point of 4%) gives zero yield of SWNTs due to oxidation of nanotubes and should be avoided.