New Application of Carbon Nanotubes. Field Emission of Electrons and Field Evaporation of C20 from Carbon Nanotubes.

Electron emission from various types of nanotubes, e.g., multiwall nanotubes (MWNTs) with capped and open ends, and single-wall nanotubes (SWNTs), was investigated by field emission microscopy (FEM). Field emission patterns originating from the pentagons placed on a cap of a nanotube were observed for the capped MWNTs with clean surfaces. Emission current versus voltage characteristics revealed that open MWNTs possess the most excellent properties as field emitters among the nanotubes investigated. As an application of nanotube field emitters, field emission displays (FED) equipped with nanotube cathodes are now attracting considerable attention. Fabrication and performance of nanotube-based FED elements are also reviewed briefly. When a positive electric potential, being an opposite potential to the case of electron emission, was applied to nanotubes, carbon clusters were directly emitted from nanotubes through field evaporation. We found that C20+ were selectively emitted from both MWNTs and SWNTs under an extremely high field over 10 V/nm.