Ranges and fragmentation behavior of fullerene molecules: A molecular-dynamics study of the dependence on impact energy and target material

Using molecular-dynamics simulation, we study the impact of C60 fullerene molecules with energies up to several tens of keV on various target materials: graphite, fullerite, Au and a condensed Ar solid. The analysis is based on single impact events. For all the target materials, fragmentation of the fullerene projectile sets in at around 1 keV impact energy; it starts the earliest in the heavy Au target. Full atomization of the projectile is observed at around 10 keV impact energy.The projectile ranges, on the other hand, depend strongly on the target material. The highest ranges are achieved in the weakly bonded Ar target. Also ranges in the fcc-C60 solid are systematically larger than in the graphite target. Interestingly, at energies above 5 keV, the fullerene penetrates deeper into the Au target than into graphite, even though the Au has a considerably higher mass and efficiently reflects the fullerenes at lower bombarding energies; this indicates the dominant role of the cohesive energy of the target.The energy dependence of fullerene molecules is surprisingly flat and varies between E1/3 and E2/3 at smaller impact energies, E < 10 keV. At higher impact energies, where the projectile has been fully atomized, the energy dependence becomes more pronounced, ∝E.