AVS 47th International Symposium
    Nanotubes - Science and Applications Tuesday Sessions
       Session NM+NS-TuM

Paper NM+NS-TuM11
Initial Growth Study of Well-aligned Carbon Nanotubes on Fe-coated Silicon Substrate by MWCVD Process

Tuesday, October 3, 2000, 11:40 am, Room 309

Session: Carbon Nanotubes: Synthesis
Presenter: C.-Y. Wen, National Taiwan University
Authors: C.-Y. Wen, National Taiwan University
L.C. Chen, National Taiwan University
C.S. Shen, National Taiwan University
Y.F. Chen, National Taiwan University
K.H. Chen, Institute of Atomic and Molecular Sciences, Taiwan
Correspondent: Click to Email
Synthesis of well-aligned carbon nanotubes (CNTs) on a large area unveils the possibility to explore their properties and applications. Many synthesis methods have been reported for the growth of CNTs. Generally, it is relatively easy to generate aligned CNTs by the CVD processes. In our study, well-aligned multi-walled CNTs have been synthesized on 70 Å iron-coated silicon substrate by microwave plasma enhanced chemical vapor deposition process, wherein methane was used as carbon source. To further investigate the growth mechanism, we adopted ex-situ microscopic observation of the CNTs grown in very short growth time of several seconds. The high-resolution SEM image shows that clusters formed at the very initial stage. As the growth time extended to 40 seconds, the back-scattering image shows that metal particles were present at the tips of CNTs while metal cones appeared in the root of CNTs. After careful Ar ion beam thinning, CNTs specimens without contamination were analyzed by high-resolution TEM. The HRTEM image indicates that the clusters were precipitated iron particles of about 10 nm in diameter and graphene layers surrounded each of them. The iron precipitation continued to form cones and part of the iron was separated and encapsulated at the tip of CNTs. The growth mechanism of CNTs could be proposed from these microscopic observations. We attempt to postulate the growth kinetics of CNTs and diffusion paths of carbon species and the catalyst iron.