Thin Multiwall Carbon Nanotube Field Emitters with Microchannel Plate for High Current Emission

Abstract

ABSTRACTWe report a method to amplify the electron current of carbon nanotube field emitter cathode using an electron multiplier and synthesis of thin multiwall carbon nanotubes by thermal chemical vapor deposition. A commercial microchannel plate which is an array of microscopic electron multipliers was used for this purpose. A microchannel plate placed between the cathode and anode amplified the current and also acted as protection shield for nanotubes during vacuum arcing. The turn-on field was approximately 1 V/µm for both cases, but current obtained was 3 times higher and the field was also lower. The increase in current is attributed to the electron multiplication, and to the increase in field enhancement factor from 9296 to 12815 (37%) with microchannel plate. The thin multiwall carbon nanotubes were synthesized using Mo/Fe catalyst solution. The inner and outer wall diameters of the nanotubes were in the range of 2.5-5 nm and 7-15 nm respectively, determined by Raman spectroscopy and transmission electron microscopy. The nanotubes had excellent field emission property which is attributed to their thin wall diameters ∼10 nm, high aspect ratio of 1500 and the high field enhancement factor of 9296. The emission current was stable with an average fluctuation of 2%.