Effects of microscopic features on field emission of aligned carbon-nanotube-bundle array

Carbon nanotube (CNT) is a type of ideal cathode materials for field emission (FE) devices. Its outstanding field emission properties can be attributed to high field enhancement on the tip due to its large aspect ratio.
^[1]
Early works reported that the field enhancement of CNTs in an array is strongly suppressed due to the screening effect.
^[2]
Further study confirmed that to avoid the screening effect, the distance between two neighboring CNTs is at least twice of the height of the CNTs.
^[3]
Wei
^[4]
and Tu
^[5]
independently developed techniques for growth of individual CNT aligned vertically on the substrate surface. However, individual CNT often has difficulty in standing straight on a substrate without the support. Alternatively, one may grow CNT bundle array. In this paper, we report our findings on the FE properties of the cone-shape CNT bundle arrays with different bundle density.