Electron source design with CNT field-emitter cathode

Micro-sized electron source with field-emitter cathodes plays an important role for new vacuum triode applications. For these general applications an all-purpose electron source with carbon nanotube (CNT) field emitter and control grid for 10 mA was designed, developed and investigated. The miniaturization of the electron source was achieved by the use of a carbon nanotube field-emitter cathode (CNT buckypaper) and a micro grid, with a distance of only some ten micro-meters. Because of the threshold field strength for field emission of CNTs being in the range 1 ... 4 Vμm^-1, the grid voltage can be low. In our contribution we discuss the influence of the micro grid on electron source properties, especially anode-field penetration through the micro grid, and micro-lensing effect.