The Ultimate Electron Sources Using Millimeter Long Carbon Nanotubes

We are reporting the fabrication of a very efficient electron source using long and crystalline carbon nanotubes. These devices start to emit electrons at fields as low as 0.10 V/$\mu $m and reach threshold emission at 0.164 V/$\mu $m. In addition, these electron sources are very stable for long operation periods up to 200 hrs and can achieve peak current density of 2 Acm$^{-2}$ at only 0.28 V/$\mu $m. To demonstrate intense electron beam generation, these devices were used to produce white light by cathodoluminescence. Finally, to rational the measured properties in open carbon nanotubes of different lengths we used density functional theory. The modeling establishes a clear correlation between length and field enhancement factor.