Microstructural analysis of carbon films obtained from C60 fullerene ion beams

Carbon films have been produced by accelerating C60+ ions on silicon substrates with energies between 100 and 800 eV. Furthermore some samples have been vacuum-annealed at 600 °C. The samples have been characterized by Raman and positron annihilation spectroscopies (RS–PAS). The measurements for the as-deposited material show that there is a coexistence of polymerized fullerenes and amorphous-carbon islands and that the structure depends on the energy of the incident ions. At low energies, fullerenes are deposited preserving the molecular identity and some intermolecular covalent bonds begin to insinuate; at higher energies, the amount of these covalent bonds increases and the amorphous islands predominate. After the annealing process, the amorphous phase organizes in graphitic clusters and the unbroken C60 cages are transformed back to pristine and slightly polymerized C60.