Field Emission of Electrons from Carbon Nanotubes with Extremely Sharp Tips and Its Application to Electron Sources

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Carbon nanotubes possess physical and chemical properties favorable for field emitters. In this study, fundamental properties of field emission from carbon nanotubes are elucidated, and nanotube-based field-emission display devices are experimentally manufactured and their performance is examined.1. Electron Emission from Carbon Nanotubes Studied by Field Emission Microscopy (FEM)Field Emission from a variety, of carbon nanotubes, e.g., multiwall nanotube (MWNT), nanografiber (NGF), and single-wall nanotube (SWNT), was investigated by using an FEM apparatus constructed newly. Among the nanotubes studied, oxidized MWNTs with open tips exhibited the most excellent emission properties, and purified SWNTs and NGF were the next good emitters.2. Electron Emission from Films of Carbon Nanotubes Spread on Cathode PlatesWhen the gap between the nanotube cathode and the grid was 1 mm and the grid voltage was 750 V, current density of 2.5 mA/cmィイD12ィエD1 as obtained for NGF, and approximately 0.1 mA/cmィイD12ィエD1 for MWNT and SWNTs.3. Effects of Ambient Gases on Lifetimes of Nanotube EmittersLife tests of MWNT emitters performed under ambient gases of oxygen, water, nitrogen and argon revealed that oxygen was the most hazardous gas for nanotube emitters.4. Fabrication of Nanotube-Base Field Emission Display Elements and Their PerformanceCathode ray tube (CRT) lighting-elements were manufactured by replacing conventional thermionic cathodes with nanotube field emitters. Stable electron emission, high emission current with low electric field (〜10 mA/cmィイD12ィエD1 at 1.5 V/μm), and long life of the emitters were demonstrated.