Aligned　carbon　nanotubes　were　grown　by　plasma-enhanced　hot　filament　chemical　vapor　deposition　using　different　reaction　gases　and　they　were　investigated　by　scanning　electron　microscopy　and　transmission　electron　microscopy.　It　is　found　that　the　hollow　carbon　nanotubes　were　formed　using　methane　and　hydrogen　as　the　reaction　gases,　but　the　bamboo-structured　carbon　nanotubes　were　grown　when　ammonia　was　added　into　the　reaction　gases,　indicating　that　the　structure　of　the　aligned　carbon　nanotubes　was　changed　depending　on　different　reaction　gases.　On　setting　of　diffusion　of　carbon,　the　effects　of　the　nitrogenous　gas　on　the　structure　change　of　carbon　nanotubes　are　studied.　(c)　2006　Elsevier　B.V.　All　rights　reserved.