Brightness of electron beam emitted from a single pentagon on a multiwall carbon nanotube tip

A capped multiwall carbon nanotube with a clean surface gives field emission patterns consisting of six pentagonal rings corresponding to pentagons located at the tip. To evaluate the optical properties of a single pentagon as an electron source, the I-V characteristics and angular current densities for a single clean pentagon have been measured by probe-hole-type field emission microscopy. Reduced brightness estimated from the angular current density and the geometrical size of the pentagon reached similar to5.6 x 10(9) A m(-2) sr(-1) V-1 at an emission current of 53 nA. This value is one order of magnitude or more higher than that of an individual multiwall carbon nanotube field emitter reported by Jonge et al. Copyright (C) 2004 John Wiley Sons, Ltd.