Nanotube Epitaxy

A review is presented of the organization of carbon nanotubes by substrate-directed growth on crystal surfaces. The production of ordered carbon nanotube arrays on surfaces is a critical prerequisite for their large-scale integration into nanocircuits. We have recently elaborated a series of surface-directed mechanisms of carbon nanotube growth, which can be classified as different modes of ``nanotube epitaxy''. These epitaxial modes of carbon nanotube growth include ``lattice-directed epitaxy'' (by atomic rows), ``ledge-directed epitaxy'' (by atomic steps) [1], and ``graphoepitaxy'' (by nanofacets) [2]. Some of these epitaxial modes can be simultaneously combined with electric-field directed growth [3] for the orthogonal self-assembly of carbon nanotube crossbar architectures [4]. Nanotube epitaxy with different crystal surfaces yields unprecedented carbon nanotube array morphologies, including highly straight, kinked, wavy, crossbar, serpentine [5], and more. [1] Ismach, et al., \textit{Angew. Chem. Int. Ed.} \textbf{2004}, $43$, 6140. [2] Ismach at al. \textit{J. Am. Chem. Soc.} \textbf{2005}, $127$, 11554. [3] Joselevich et al., \textit{Nano Lett.} \textbf{2002}, $2$, 1137. [4] Ismach et al. \textit{Nano. Lett. }\textbf{2006}, $6$, 1706. [5] Ismach et al., in preparation.