title: Optical performance of carbon-nanotube electron sources.
abstract: The figure of merit for the electron optical performance of carbon-nanotube (CNT) electron sources is presented. This figure is given by the relation between the reduced brightness and the energy spread in the region of stable emission. It is shown experimentally that a CNT electron source exhibits a highly stable emission process that follows the Fowler-Nordheim theory for field emission, fixing the relationship among the energy spread, the current, and the radius. The performance of the CNT emitter under realistic operating conditions is compared with state-of-the-art electron point sources. It is demonstrated that the reduced brightness is a function of the tunneling parameter, a measure of the energy spread at low temperatures, only, independent of the geometry of the emitter.
authors.affiliation: Philips Research, Professor Holstlaan 4, 5656 AA Eindhoven, The Netherlands. dejongen@ornl.gov
authors.forename: Niels
authors.initials: N
authors.lastname: de Jonge
authors.forename: Myriam
authors.initials: M
authors.lastname: Allioux
authors.forename: Jim T
authors.initials: JT
authors.lastname: Oostveen
authors.forename: Kenneth B K
authors.initials: KB
authors.lastname: Teo
authors.forename: William I
authors.initials: WI
authors.lastname: Milne