Abstract
The effect of Ni thickness and microwave power on the growth of carbon nanotubes (CNTs) by microwave-heated chemical vapor deposition is reported. A 5-100-nm-thick nickel layer was deposited with an e-gun in a vacuum of 10 -6 Torr. It was found that the diameter and length of CNTs increase with Ni layer thickness. The emission I-V curves clearly show two groups of characteristics marked off at the Ni thickness of 50 nm. The low field emission for those films grown on nickel thickness below 50 nm is consistent with the carbonaceous particles and carbon overlayers observed using SEM. The microwave power that determines the substrate temperature also affects the morphology and emission property of CNT films. A CNT film grown on 80-nm-thick Ni layer at 900 W for 18 min has shown excellent emission characteristics with very low turn-on field of 0.056 V/μm and a high current density of 160 mA/cm 2 at 4.5 V/μm, which is comparable to the best field emission samples ever reported. © 2003 Elsevier Science B.V. All rights reserved.