Carbon nanotubes: nanomechanics, manipulation, and electronic devices

Carbon nanotubes are novel materials with unique electrical and mechanical properties. Here we present results on their atomic structure and mechanica l properties in the adsorbed state, on ways to manipulate individual nanotu bes, on their electrical properties and, finally, on the fabrication and ch aracteristics of nanotube-based electron devices. Specifically, atomic forc e microscopy (AFM) and molecular mechanics simulations are used to investig ate the effects of van der Waals interactions on the atomic structure of ad sorbed nanotubes. Both radial and axial structural deformations are identif ied and the interaction energy itself is obtained from the observed deforma tions. The conditions under which the structure of a nanotube will adjust t o the topography of the substrate are defined. We show that the strong subs trate-nanotube interaction allows the manipulation of both the position and shape of individual nanotubes at inert surfaces using the AFM. AFM manipul ation is then utilized to position individual nanotubes on electrical pads so that their electrical characteristics can be evaluated. We demonstrate t he operation of a field-effect transistor based on a single semiconducting nanotube and of a single-electron transistor using a nanotube bundle as Cou lomb island. Finally, conducting nanotubes are employed as tips for AFM lit hography. (C) 1999 Elsevier Science B.V. All rights reserved.