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Fig. 20.21. The principle of moving C^ molecules by a rotating external electric field. An isolated molecule is assumed to be adsorbed on an ideally flat, weakly polar substrate. A rotating external electric field induces a dipole moment that exceeds the effect of the substrate dipoles on the molecule; the successive directions of the field are shown in (a) through (d). The large diameter of the molecule should allow coupling to successive poles, thereby generating lateral movement [20.119].

To interconnect these nanoscale devices, it may someday be possible to utilize carbon nanotubes for nanowire applications. As discussed in ยง19.5, by varying the chirality and diameter of carbon nanotubes, it should be possible to alter their properties from metallic to semiconducting to insulating. Such nanotubes could, in their own right, lead to nanoscopic electronic devices based on concentric semiconducting and metallic carbon tubules as shown in Fig. 20.22. The significance of carbon nanotubes as electronic materials is the demonstration of quasi-ID cylindrical wires with a large aspect (length-to-diameter) ratio, thereby opening a new field of ID physics for the study of ID cylindrical wires or hollow tubes. There is also the possibility of the application of nanotubes filled with appropriate guest species with regard to low-dimensional transport, magnetism, and superconductivity. The

Device Applications of Graphene Tubules

" Metallic Wire"

" Metallic Wire"

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