Vacuum-Breakdown-Induced Needle-Shaped Ends of Multiwalled Carbon Nanotube Yarns and Their Field Emission Applications

The Joule-heating-induced vacuum breakdown of the carbon nanotube (CNT) yarns was studied. Wall-by-wall breakdown and superplastic deformation of CNTs are the main physical processes at the hottest location before breakdown. The two ends at the breaking point are needle-shaped with surfaces rich in tightly compacted conelike CNT bundles with a single CNT at the tips. Both of the ends can provide emission currents of over 150 μA within an area 5 μm in diameter; the cathode ends start field emission at a lower voltage. Laser irradiation was introduced to control the breaking location making the methodology more practical. Small pixels were constructed with the yarn emitter cathodes, which are potentially building blocks of large outdoor displays.