Strong Field Enhanced Thermionic Electron Emission from a New Oxide Coated Carbon Nanotube Cathode

Summary form only given. We have developed a new type of field enhanced thermionic cathode. This cathode is capable of emitting much higher electron current, because of the strong field enhancement factor induced by incorporating needle like geometrical feature into the cathode structure. Field enhancement effect is usually negligible for conventional thermionic cathodes. However, in this case significant field enhancement thermionic emission is induced by introducing sharp carbon nanotubes tips. The cathode consists of a metal coil/substrate with carbon nanotubes grown on top of its surface by plasma enhanced CVD technique. The carbon nanotubes are further coated with thermionic emission materials (BaO/SrO/CaO) - a typical thermionic emission material system used in fluorescent lighting and many other applications. The oxides are coated on carbon nanotubes by magnetron sputter deposition and spin coating techniques. During operation, the cathode is heated up to a thermionic emission temperature by flowing an electric current through the metal coil. The emission current and current density from this cathode are found at least an order of magnitude higher than conventional thermionic cathode coated with same emission materials and operated at same temperature. We will present comparison results on electron emission for three different cathodes: 1) oxide coated carbon nanotube cathode, 2) conventional oxide cathode, and 3) carbon nanotube cathode