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.