AVS 49th International Symposium
    Nanotubes: Science and Applications Topical Conference Monday Sessions
       Session NT-MoA

Paper NT-MoA4
The Fabrication and Characterization of Carbon Nanotube Nanoelectrode Array for Chemical/Biosensor Applications

Monday, November 4, 2002, 3:00 pm, Room C-209

Session: Nanotubes: Chemical Functionalization, Sensors
Presenter: J. Li, NASA Ames Research Center / Eloret Corp.
Authors: J. Li, NASA Ames Research Center / Eloret Corp.
R. Stevens, NASA Ames Research Center / Eloret Corp.
H.T. Ng, NASA Ames Research Center / SETI Institute
L. Delzeit, NASA Ames Research Center
A. Cassell, NASA Ames Research Center / Eloret Corp.
C. Nguyen, NASA Ames Research Center / Eloret Corp.
B. Chen, NASA Ames Research Center / Eloret Corp.
J. Han, NASA Ames Research Center / Eloret Corp.
M. Meyyappan, NASA Ames Research Center
Correspondent: Click to Email
Nanoelectrode arrays are attractive electroanalytical tools with the potential to provide much higher sensitivity for chemical and biosensor applications. So far nanoelectrode arrays/ensembles were prepared by template synthesis using nanoporous membranes or nanoscale defects created in the self-assembled organic monolayers on an Au surface. We report here on a new approach to fabricate solid-state nanoelectrode array/ensemble by bottom-up scheme using well-aligned multi-walled carbon nanotube arrays on a conducting substrate. Carbon nanotubes were grown on a substrate prepatterned with metal catalysts. The density can be controlled precisely with e-beam lithography. The alignment, diameter, and length can be controlled by plasma CVD process. Dielectric material such as SiO2 was then filled into the gap between carbon nanotubes by TEOS CVD to insulate the sidewall of the carbon nanotubes as well as the conductive underlayers. This method also provides an added advantage by which the mechanical strength of the carbon nanotube array is dramatically improved. An aggressive mechanical polishing can thus be applied to planarize the surface, resulting in a flat surface with only the ends of carbon nanotubes exposed. SEM indicates that carbon nanotubes remain their integrity during these processes. AFM shows that carbon nanotubes extend out of the insulating matrix by a few nanometers due to the higher mechanical strength. The electrical properties of individual carbon nanotubes in the array are thoroughly characterized with current sensing AFM and I-V measurements. Both of metallic and semiconducting properties were observed, strongly depending on the growth conditions. Thus fabricated carbon nanotube array is essentially an ideal nanoelectrode array with graphite edge-plane like nanoelectrodes distributed in a controlled way. The electrochemical properties and the application of these nanoelectrode arrays as chemical and biosensors will be discussed.