Ion-beam-induced modification of fullerene films as studied by electron-energy-loss spectroscopy

The ion-beam (2 keV Ar) -induced amorphization of thin fullerene films has been studied by in situ electron-energy-loss spectroscopy (EELS). With due care to the electron-beam current, the EELS spectrum may be measured without degradation during the electron bombardment to provide an EELS fingerprint of C₆₀ films. The diminution of the intensity of characteristic peaks in the EELS spectrum upon ion impact was used to deduce a cross section for the destruction of the C₆₀ molecules of (0.85±{}0.2)×{}10^-14 cm². This value corresponds closely to the geometric size of one C₆₀ molecule, suggesting that each incident Ar ion destroys one C₆₀ molecule upon ion impact. This cross section is somewhat smaller than that expected using scaling arguments from the results of more energetic ion bombardment (100-300 keV). The difference may be due to surface processes, which become important for low-energy ion-beam irradiation.