Growth and Characterizations of Well-Aligned Carbon Nanotubes

Abstract

Large arrays of well-aligned carbon nanotubes are first made possible on substrates in 1998 by plasma enhanced chemical deposition [1, 2] in which the diameter and length of each carbon nanotube are under control, but not the growth angle, location, nor the spacing between them. Soon after, the titled growth has been achieved by controlling the plasma direction using the same growth technique [3], Almost at the same time, the control of location and spacing of the nanotubes have been accomplished using electron beam (e- beam) lithography to pattern the nickel dots first at where they are needed and then to grow the carbon nanotubes using the same growth technique [4, 5]. However, e-beam is not possible to be commercialized for large scale. Therefore, alternative cheap and scalable technique is sought. Fortunately, the catalytic dots have been fabricated by electrochemistry and excellent aligned carbon nanotubes arrays have been grown [6]. Due to the nature of electrochemistry, the control on location of each nanotube is lacking. For applications that do not require the pre-determined location of each nanotube such as regular electron source, the arrays grown using the dots by electrochemistry is good enough. However, for applications that do require the pre-determined location of each nanotube such as microscopic probing tips, nanophotonics, etc., the control of location of each nanotube is crucial. Recently, we have been successful to grow large arrays of carbon nanotubes with diameter, length, location, and spacing under control by a simple and scalable technique, nanosphere lithography [7]. Since the very first report on large arrays of well-aligned carbon nanotubes, numerous papers have used the same or a slightly modified technique to grow aligned carbon nanotube arrays by either DC or microvave plasma CVD [8–18].