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 β exhibit three ranges: low (β∼10), medium (β∼100) and high (β>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 Vto also depends on the tip structure and the lowest Vto occurs in open-tipped-with-oblique-angle CNTs. The geometrical enhancement factor depends on the tube geometry via a linear equation β=β0(1+d/kr) with k≈40 and β0 equals 163 and 53 for the high-β and medium-β 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.