Fig. 2.

Molecular O₂-assisted growth of vertical SWNT towers and sheets with submicrometer dimensions. (A) A SEM image showing SWNT towers with various widths (20 μm, 5 μm, 1 μm, 500 nm, and 300 nm from left to right in the lower region of the image) and vertical SWNT sheets (20 μm, 5 μm, 1 μm, 500 nm, 300 nm, and 100 nm thick from top to bottom of the upper part of the image) after 30 min of growth. (B) An AFM image of the patterned catalyst strips (bright 300-nm and 100-nm-wide regions) composed of densely packed Fe nanoparticles used for the growth of the 300-nm and 100-nm-thick vertical SWNT sheets (pointed to by arrows) in A. (C) An AFM image of two of the patterned catalyst squares (300 nm in width) used for the growth of the smallest towers (pointed to by an arrow and tilted due to high aspect ratio) in A. (D and E) Two SEM images of square and circular towers and lines of V-SWNTs, each from different growths than the sample in A, to show the reproducibility of the synthesis.