High-resolution direct observation of the carbon-cage structure of C₆₀ buckyballs

In C₆₀ films containing higher fullerene derivatives and having electrically conducting islands, it has been possible for the first time to observe, using high resolution scanning tunnelling electron microscopy (STM), the individual carbon cage of C₆₀ buckyballs forming a f.c.c. lattice on a silver-coated glass substrate. The observed images of the molecule are surprisingly distinct and not smeared out, indicating their ambient-temperature reorientational motion to be pinned. The possible causes of the freezing are: (i) the presence of higher fullerene derivatives; (ii) changes in the electronic structure of the films due to interaction and proximity of Ag atoms; and (iii) the pinning of the molecules by the presence of large electric field gradients between the STM tip and the sample surface, a factor which, in addition, is considered responsible for the distortion observed in the buckyball images.