New technique for fabrication of individual carbon-nanotube field emitters

Abstract

Currently, field emission experiments on individual carbon nanotubes (CNTs) are carried out by placing the CNTs inside a transmission electron microscope. In this work we report an alternative method of fabricating and measuring individual multiwalled CNT-field emitters fabricated on a silicon substrate by the e-beam lithography technique. A field emission experiment is then performed in a high-vacuum system for CNTs with various radii, lengths, interelectrode separations and tip structures. The geometrical enhancement factors beta exhibit three ranges: low (beta similar to 10), medium (beta similar to 100) and high (beta > 200) depending on whether the CNT tip is closed-tipped, open-tipped with a flat end or open-tipped with an oblique-angle end, respectively. The turn-on voltage V-to also depends on the tip structure and the lowest V-to occurs in open-tipped-with-oblique-angle CNTs. The geometrical enhancement factor depends on the tube geometry via a linear equation beta = beta(0)(I + d/kr) with k approximate to 40 and beta(0) equals 163 and 53 for the high-beta and medium-beta lines, respectively, where r is the radius and d is the CNT tip-anode spacing. The new method may open a path leading to the integration of nanotube field emitters with other miniature devices using semiconductor integrating technology.