Synthesis of aligned carbon nanotubes using thermal chemical vapor deposition

Aligned carbon nanotubes have been synthesized on transition metal-coated silicon substrates with C2H2 using thermal chemical vapor deposition. It was found that nanotubes can be mostly vertically aligned on a large area of plain Si substrates when the density of metal domains reaches a certain value. Pretreatment of Co–Ni alloy by HF dipping and etching with NH3 gas prior to the synthesis is crucial for vertical alignment. Steric hindrance between nanotubes at an initial stage of growth forces nanotubes to align vertically. Nanotubes are grown by a catalyst-cap growth mechanism. Applications to field emission displays are demonstrated with emission patterns.