Characterization of bias-controlled carbon nanotubes

摘要

In this study, we docus on the immediately mproving quality of gowing 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 + 80V) to 120 nm (under -120V). Raman specturums indicate that I_D/I_G ratio decreases with increasign positive bias. This implies applying positive bias could enhance the graphitizaion of carbon nanotubes. However, positive and negatve 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.