Calculated energy loss of a swift fullerene ion beam in InP

Abstract

Bombardment of semiconductors with fullerene has been used to induce the formation of tracks. It is now accepted that target electronic excitation and ionization, which gives rise to the slowing down of the projectile is essential to calculate the track diameter. In the case of cluster beams, like fullerenes, the electronic excitation induced by each of the cluster constituents is enhanced, for certain projectile energies and target depths, by the so-called vicinage effects. Here we use a simulation code to calculate the energy lost by a swift fullerene ion beam in InP, paying special attention to the vicinage effects where they are significative. The code describes classically the movement of each cluster constituent under the influence of the self-retarding force, the Coulomb repulsion among molecular fragments, the wake forces responsible for the vicinage effects and the multiple scattering with the target nuclei. The simulation code also takes into account the possibility that the molecular fragments can also capture or loss electrons from the target, changing its charge state in their travel through the solid. Our simulations show that the energy deposited by the atomic ions that constitute the C60 ion is clearly higher than the energy deposited by the same atomic ions but isolated. This difference being larger as the incident energy increases. We have predicted that track diameters of ∼244Å can be obtained in an InP target when using C60 ions with an initial energy of 300 MeV.