Nature 359, 707 - 709 (22 October 1992); doi:10.1038/359707a0

Curling and closure of graphitic networks under electron-beam irradiation

Daniel Ugarte

Institut de Physique Expérimental, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland

THE discovery¹ of buckminsterfullerene (C₆₀) and its production in macroscopic quantities² has stimulated a great deal of research. More recently, attention has turned towards other curved graphitic networks, such as the giant fullerenes (C_n, n > 100)^3,4 and carbon nanotubes^5–8. A general mechanism has been proposed⁹ in which the graphitic sheets bend in an attempt to eliminate the highly energetic dangling bonds present at the edge of the growing structure. Here, I report the response of carbon soot particles and tubular graphitic structures to intense electron-beam irradiation in a high-resolution electron microscope; such conditions resemble a high-temperature regime, permitting a degree of structural fluidity. With increased irradiation, there is a gradual reorganization of the initial material into quasi-spherical particles composed of concentric graphitic shells. This lends weight to the nucleation scheme proposed⁹ for fullerenes, and moreover, suggests that planar graphite may not be the most stable allotrope of carbon in systems of limited size.

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