Document Type

Article

Journal/Book Title/Conference

Journal of Applied Physics

Volume

112

Issue

12

Publication Date

2012

First Page

124303

DOI

http://dx.doi.org/10.1063/1.4768928

Abstract

Beneath the seeming straight-forwardness of growing carbon nanotube(CNT) forests by the injection chemical vapor deposition(CVD) method, control of the forest morphology on various substrates is yet to be achieved. Using ferrocene dissolved in xylene as the precursor, we demonstrate that the concentration of ferrocene and the injection rate of the precursor dictate the CNT density of these forests. However, CNT density will also be affected by the substrates and the growth temperature which determine the diffusion of the catalyst adatoms. The CNT growth rate is controlled by the temperature and chemical composition of the gases in the CVD reactor. We show that the final height of the forest is diffusion limited, at least in the conditions of our experiments. Because of the proximity and entanglement of the CNTs in a forest, the growing CNTs can lift-up the inactive CNTs resulting in reduced density toward the base of the forest unless the nucleation rate of the new catalyst particles is sufficiently high to replenish the inactive catalyst particles. Significant loss of CNT attachment by the lift-up effect reduces the adhesion of the forest to the substrate. Optimizing the ferrocene concentration in the precursor, precursor injection rate, gas mixture, substrate, and temperature is necessary to achieve desired forest morphology for specific applications.

Comments

Published by the American Institute of Physics in the Journal of Applied Physics. Publisher version is available for download through link above. Paper is coauthored by student and faculty researchers at Utah State University, Department of Physics.

This work was supported by a grant from Space Dynamics Laboratory. RWC and CM acknowledge the support from Eccles Foundation and various graduate and undergraduate research fellowships from Utah State University.