The　characteristics　of　field　electron　emission　(FE)　from　aligned　carbon　nanotubes　(ACNTs)　in　a　form　of　film,　which　were　catalytically　grown　by　plasma-enhanced　hot　filament　chemical　vapor　deposition,　were　measured　for　many　cycles.　The　results　indicate　that　the　FE　characteristic　for　every　measurement　cycle　is　different　and　it　follows　the　Fowler-Nordheim　model　in　the　low　field　region,　but　it　deviates　from　the　model　in　the　high　field　region.　The　ACNTs　were　investigated　by　energy　dispersive　X-ray　(EDX)　and　the　EDX　spectrum　shows　that　oxygen　is　adsorbed　on　the　ACNTs.　The　theory　related　to　adsorption　and　space-charge　effect　was　applied　to　analyze　the　experimental　results.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.