10.1021/nn201149y.s001 Néstor Perea-López Néstor Perea-López Bernabé Rebollo-Plata Bernabé Rebollo-Plata Juan Antonio Briones-León Juan Antonio Briones-León Aarón Morelos-Gómez Aarón Morelos-Gómez Daniel Hernández-Cruz Daniel Hernández-Cruz Gustavo A. Hirata Gustavo A. Hirata Vincent Meunier Vincent Meunier Andrés R. Botello-Méndez Andrés R. Botello-Méndez Jean-Christophe Charlier Jean-Christophe Charlier Benji Maruyama Benji Maruyama Emilio Muñoz-Sandoval Emilio Muñoz-Sandoval Florentino López-Urías Florentino López-Urías Mauricio Terrones Mauricio Terrones Humberto Terrones Humberto Terrones Millimeter-Long Carbon Nanotubes: Outstanding Electron-Emitting Sources American Chemical Society 2011 density field enhancement factor source electron beam generation carbon nanotubes device field emission properties length 2011-06-28 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Millimeter_Long_Carbon_Nanotubes_Outstanding_Electron_Emitting_Sources/2637802 We are reporting the fabrication of a very efficient electron source using millimeter-long and highly crystalline carbon nanotubes. These devices start to emit electrons at fields as low as 0.17 V/μm and reach threshold emission at 0.24 V/μm. In addition, these electron sources are very stable and can achieve a peak current density of 750 mA cm<sup>–2</sup> at only 0.45 V/μm. In order to demonstrate intense electron beam generation, these devices were used to produce visible light by cathodoluminescence. Finally, density functional theory calculations were used to rationalize the measured electronic field emission properties in open carbon nanotubes of different lengths. The modeling establishes a clear correlation between length and field enhancement factor.