Diameter dependency for the electric-field-assisted growth of carbon nanotubes

Controlling the growth orientation of carbon nanotubes (CNTs) is a topic of great importance in the integration of CNTs into micro/nanosystems. The electric field has been exploited to control the growth orientation of CNTs. In this letter, the diameter dependency of the effect of an electric field on the growth orientation of CNTs is reported. Statistical analysis of the direction and the straightness of CNTs show that the electric field has a positive effect on small-diameter CNTs, but not on large-diameter CNTs. An electrostatic and thermodynamic model is proposed for an explanation of this phenomenon. (C) 2013 AIP Publishing LLC.