Scanning tunnelling microscopy of solid C₆₀/C₇₀

Abstract

THE detection of a strong peak in mass spectra of carbon vapour corresponding to a cluster of 60 carbon atoms¹ led to the proposal that these clusters corresponded to highly symmetric C₆₀. molecules in the shape of truncated icosahedra^1,2. Recently macroscopic quantities of C₆₀ and the related species C₇₀ (thought to have an elongated cage structure) have been prepared^3,4 and purified in a solid form, called fullerite⁵. The availability of a solid form has made possible studies using infrared and ultraviolet-visible absorption spectroscopy, X-ray and electron diffraction⁵, NMR and Raman spectroscopy, all of which provide evidence that supports the proposed 'soccer ball' structure of C₆₀. Here we report the direct imaging of C₆₀ molecules in sub-micrometre-sized particles of fullerite, using scanning tunnelling microscopy. The images reveal spherical molecules, spaced about 1 nm apart, stacked in close-packed arrays. Our results give a direct demonstration of the highly symmetric structure of these clusters.