Future Directions

Scanning tunneling microscopy and spectroscopy have been used to characterize the atomic structure and tunneling density of states of individual SWNTs and SWNT ropes. Defect-free SWNTs exhibit semiconducting and metallic behavior that depends predictably on helicity and diameter. In addition, the 1D VHS in the DOS for both metallic and semiconducting tubes have been characterized and compare reasonably well with tight-binding calculations. Lastly, studies show that it is possible to access readily a regime of "0D" behavior, where finite length produces quantization along the tube axis, which opens up future opportunities to probe, for example, connections between extended and molecular systems. In short, much of the fascinating overall structural and electronic properties of SWNTs are now in hand - but this really only has scratched the surface. Future work addressing the role of defects and other structural perturbations, coupling to metal and magnetic systems, the connection between extended and finite size/molecular clusters, as well as other directions will help to define further the fundamental physics of these systems and define emerging concepts in nanotechnology.

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