Field Emission of ITO-Coated Vertically Aligned Nanowire Array

Abstract

An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

Keywords: Field emission; ITO; Nanowire; Top–down.

Figure 1

Schematic view of fabrication process of ITO-coated VANA. a Circular aperture patterns (φ = 1 μm) of Cr layer on a fused silica wafer. b SU-8 50 on Cr layer. c Backside UV exposure with exposure dose of 200 mJ/cm² filtered by a narrow band-pass filter. d SU-8 VANA after development of SU-8 and Cr etching. e Pyrolyzed carbon VANA by pyrolysis process at 900°C for 30 min. f ITO-coated VANA with 0.1-μm-thick ITO

Figure 2

SEM images of a SU-8 VANA, b pyrolyzed carbon VANA, and c ITO-coated VANA. d EDS result of ITO-coated VANA

Figure 3

a Schematic view of the experimental setup, where a Zyvex nanomanipulator is employed in a SEM vacuum chamber. b SEM image of the tungsten tip A and ITO-coated VANA with distance control by the nanomanipulator

Figure 4

a Field emission I-E curve of the ITO-coated VANA measured under a vacuum of 1.59 × 10⁻⁵ torr. b Corresponding F–N curve obtained from I-E curve. c Field emission current stability of ITO-coated VANA at 1.59 × 10⁻⁵ torr