No abstract

We determine, with excellent agreement between theory and experiment, the behavior of single wall carbon nanotubes during uniform electron irradiation. Calculations utilizing known ejection threshold energies predict that an isolated nanotube will damage preferentially on surfaces that lie normal to the electron beam. A minimum incident electron energy of 86 keV is required to remove a carbon atom by a knock-on collision for this geometry. Higher electron energies are required for any other geometry, and at energies exceeding 139 keV every atom on a nanotube is susceptible to ballistic ejection. Transmission electron microscopy observations of nanotubes using 80–400 keV electrons corroborate these conclusions. Based upon empirical observations, we also explain damage processes in nonisolated nanotubes.

No abstract

Arrays of C60 molecules nested inside single-walled nanotubes represent a class of nanoscale materials having tunable properties. We report electronic measurements of this system made with a scanning tunneling microscope and demonstrate that the encapsulated C60 molecules modify the local electronic structure of the nanotube. Our measurements and calculations also show that a periodic array of C60 molecules gives rise to a hybrid electronic band, which derives its character from both the nanotube states and the C60 molecular orbitals.