Excellent Field Emitters: Onion-Shaped Tipped Carbon Nanotubes

Large-scale synthesis of highly graphitic carbon nanotubes (with a diameter of ∼5−8 nm) from a thermal reaction of activated carbon and Bi 2 O 3 powders, which was grown via a carbon-thermal reduction and Bi catalyzed vapor−liquid−solid process has been obtained. Individual carbon nanotubes were terminated with an onion-shaped carbon tip, which has never been observed in growth of a carbon nanotube. Field emitters made from the present carbon nanotubes exhibit excellent emission properties: they can be operated at a very large current density of ∼145 mA/cm 2 at a low voltage of 5.5 V/μm, and possess a long period (>32 h) of high emission stability at a high emission current density of ∼9 mA/cm 2 and under a constant applied voltage. These properties are equally important for high image quality in field emission display fabrication. Hence, as-fabricated CNTs could act as excellent electron emitters and have great potential application in field emission panel displays.