Characterization of bias-controlled carbon nanotubes

In this study, we focus on the immediately improving quality of growing carbon nanotubes without any pre- or post-treatment. The applied biases during the reaction can directly control the diameter and the quality of carbon nanotubes. This simple step skips additional treatments and is easily used in many deposition systems. The diameter of carbon nanotubes noticeably varies from 45 nm without any amorphous carbon (under + 80 V) to 120 nm (under - 120 V). Raman spectrums indicate that I-D/I-G ratio decreases with increasing positive bias. This implies applying positive bias could enhance the graphitization of carbon nanotubes. However, positive and negative bias effects slightly vary the field emission enhancement. In addition, carbon nanotubes grown under positive bias possess better field emission characterization. This results from the following reasons: (I) smaller diameter- (II) pure surface; (III) more graphitized structure; and (IV) higher field enhancement beta. (C) 2003 Elsevier Science B.V. All rights reserved.