Thermal desorption spectroscopy of fullerene films containing endohedral Li@C₆₀

Thermal desorption spectroscopy has been carried out on thin fullerene films containing endohedral Li@C₆₀ and produced by low-energy ion bombardment. The desorption properties of the films were studied as a function of the film thickness, ion energy, and ion dose. The results provide strong corroborative evidence for the endohedral nature of the Li-containing species and also clearly indicate the prescence of Li2@C₆₀ in the films. The binding energy in these films is significantly larger than in pure C₆₀ films and evidence of degradation of the fullerenes is seen at high ion energies and/or large ion doses.