AVS 52nd International Symposium
    Nanometer-Scale Science and Technology Friday Sessions
       Session NS-FrM

Paper NS-FrM3
Well - Aligned Growth of Carbon Nanotubes/Fibers in Anodized Aluminum Oxide Pores by DC Plasma Enhanced Hot Filament Chemical Vapor Deposition

Friday, November 4, 2005, 9:00 am, Room 210

Session: Nanotube Processing and Properties
Presenter: H.W. Yap, University of Wisconsin-Madison
Authors: H.W. Yap, University of Wisconsin-Madison
B. Ramaker, University of Wisconsin-Madison
A.V. Sumant, University of Wisconsin-Madison
R.W. Carpick, University of Wisconsin-Madison
Correspondent: Click to Email
In many carbon nanotube (CNT) or carbon nanofiber (CNF) applications - such as field emission flat panel displays, it is ideal to have an ordered and dense vertically aligned dense CNT/CNF array over a large area. The anodized aluminum oxide (AAO) template is favorable since it offers uniformly spaced pores for isolated and directional growth of these CNT/CNFs. Several research groups have already reported the use of the AAO template to grow CNT/CNFs via thermal chemical vapor deposition (CVD) but they were not successful in obtaining vertical and isolated growth once they emerged from the pores. Thus, etching of the AAO had to be subsequently performed. Microwave plasma enhanced MPECVD has been shown to give better alignment, however it is not cost effective in terms of power requirements and large area deposition. Here we report a cost effective, low power alternative approach: dc plasma enhanced hot filament CVD (dcPEHFCVD). To our knowledge, this is the first successful report to grow well aligned CNTs via AAO pores using dcPEHFCVD. Here, no anodization of the aluminum, pore widening of the AAO, post growth etching of the AAO or pretreatment of the catalyst are needed. Nickel nanowires electrodeposited in the pores act as catalysts. We find that tip growth mode is dominant here. The hot filament plays an important role in dissociating hydrocarbon species as well as heating the substrate to enhance the catalyst driven CNT/CNF growth. The plasma's electric field aligns the CNT/CNFs and is responsible for most of the growth chemistry. High resolution transmission electron microscopy reveals that both CNTs and CNFs are formed via the tip growth mode and have graphitic walls. The majority of CNTs have hollow interiors but some CNFs exhibit herringbone - like fringes in the interior. AFM images of the tubes are obtained and provide quantitative measurement of the length variations of the tubes.