Comparative Study of Three Different Chemical Vapor Deposition (CVD) Techniques of Carbon Nanotube Growth on Diamond Films.

摘要

Successful attachment of carbon nanotubes (CNTs) on diamond substrates can lead to unique power devices with superior thermal and electronic properties. However, there is very little investigation on the diamond-CNT structures, and on suitability of different growth methods. This study addresses that gap by investigating three potential Chemical Vapor Deposition (CVD) techniques for growing CNTs on diamond, and comparing their effectiveness. The diamond substrate is a commercially grown polycrystalline film. The CNT growth techniques that have been compared are as follows: thermal CVD (T-CVD), microwave plasma enhanced CVD (MPE-CVD), and floating catalyst thermal CVD (FCT-CVD). The first two approaches require pre-deposition of catalyst sources prior to CNT growth, while the last method feeds the catalyst continuously during the CNT growth process. Scanning Electron Microscopy (SEM) and high resolution Transmission Electron Microscopy (TEM) have been used to analyze the morphology and topology of the CNT structures. Raman spectroscopy was used to assess the quality of the grown CNTs by determining the D-peak to G- peak intensity ratios. Sonication tests were performed to provide qualitative comparisons of the durability of the CNT forests. T-CVD provides the largest diameter tubes with catalysts residing mainly at the CNTs/diamond interface, the MPE-CVD provides non-uniform defective CNTs, and the FCT-CVD provides the smallest diameter CNTs with catalyst particles imbedded throughout the length of the nanotubes. The three different CNT growth methods have been discussed in light of our current understanding of CNT growth mechanisms on the synthetically grown polycrystalline diamond film.