Stopping of energetic argon cluster ions in graphite: Role of cluster momentum and charge

Abstract

We show that the implantation depth for argon clusters in graphite scales linearly with cluster momentum. A plot of implantation depth versus the momentum scaled with the projected surface area of the cluster falls on the same universal plot as that shown for semiconductor and metallic clusters, thus providing a universal scaling law for cluster implantation. Molecular dynamics simulations provide some insight to the mechanisms behind the empirical observation.

Implantation of keV-energy argon clusters and radiation damage in diamond

“…3 However, recent experiments of cluster implantation supported by molecular dynamics (MD) simulations demonstrated that a universal dependence of the cluster stopping can be reached at least for graphite. 12,13 It was proved that R p can be linearly scaled with the square root of cluster kinetic energy E kin , which is proportional to cluster momentum.…”

“…The higher level of amorphization of these samples compared to the ones implanted by the lower-energy clusters (4 and 9 keV) leads to the situation where the amorphous carbon can be etched just by the thermal annealing, similar to the case of cluster-implanted graphite. 12,13 At elevated temperatures, carbon atoms undergo chemical reactions with oxygen, yielding volatile compounds. Thus, the triangular pits on the samples implanted with energies of 12 and 15 keV appear directly after the annealing.…”

“…The same scaling law was obtained for clusters of various species (Ag, Au, Si, Co, and Ar) and different sizes implanted in graphite. 12,13,28 Momentum was found to be an important parameter for understanding the physical picture of cluster stopping in matter. 13 It includes such quantities as velocity and mass.…”

“…12,13,28 Momentum was found to be an important parameter for understanding the physical picture of cluster stopping in matter. 13 It includes such quantities as velocity and mass. The velocity affects both the development of collision cascades and the final R p of the constituents.…”

“…The mass of the cluster not only contributes to the stopping and ranges of the projectiles but also defines the cluster-surface interaction area, which is related to the cluster cross section and thus to its size and mass. 12,13 This area is very important for the estimation of the radiation-damaged region formed in the target. The difference in depth between the experimental and simulated curves in Fig.…”