Field electron emission from carbon nanotubes shows promising application potential in devices. Low adhesive bonding strength between the carbon nanotubes and the substrate presents a practical challenge in environments such as high field emission current density. In this paper, we report on the performance of a carbon nanotube microbundle attached to a tungsten needle by a uniform glue layer. The device is easily fabricated without complex fixture and possesses a complete array structure. After curing the glue in air, the adhesive strength between the carbon nanotubes and the needle is over 2000 N/cm2. Field emission measurements demonstrate that the maximum current density of the emitters is over 20 A/cm2 under a low applied field (<0.4 V/μm). The emitter with high current density, low emission field, and good stability has a wide range of applications in flat displays, X-ray tubes, and lamps.

The fabrication, properties, and applications of vertically aligned carbon nanotube (VACNT) microbundle arrays with different length-to-diameter ratios were investigated. VACNT microbundle arrays with different length-to-diameter ratios from 4:1 to 30:1 and microscaling of carbon nanotube blocks were fabricated using pulsed laser ablation technology. These VACNT microbundle arrays had a very low threshold field (0.117 V/μm), excellent time stability, and high field emission current densities (137.91 A/cm2). These values are superior to those of carbon nanotubes grown directly on a silicon substrate. The large length-to-diameter ratio and the small diameter of the VACNT microbundles are considered to be the main reasons for the excellent field emission performance.