Abstract
The effect of growth temperature (600-750 °C) and growth time on the field emission properties and microstructure of carbon thin films grown using microwave-heated CVD process and Ni as catalyst, was investigated. It was found that the 600 °C, 20 min grown and 650 °C, 10 min grown films consist of mixed carbon nanostructures: mainly amorphous carbon nanowires, and a few of hollow and 'bamboo-like' multi-walled carbon nanotubes. To the contrary, as the growth temperature was increased to 700-750 °C, long growth time of 20 min was needed and mainly multi-walled carbon nanotubes of high graphite quality were produced. Field emissions of the 700 and 750 °C grown carbon films show higher turn-on fields of 2.3-3.9 V/μm, as compared to the much lower turn-on fields of <1 V/μm for the 600 and 650 °C grown carbon films. The improvement of emission characteristics in lower-temperature-grown films can be attributed to the larger field enhancement effect induced by the inhomogeneous electronic sp <sup>2</sup> /sp <sup>3</sup> structures and the hydrogen termination on amorphous carbon nanowires. © 2004 Elsevier B.V. All rights reserved.