Surface Ripple Formation by Bombardment with Clusters: Influence of Mass

Abstract

Nanostructure formation on Co(110) surfaces was studied by using irradiation with cluster ion beams with oblique incidence and an energy of 250 eV/atom. In this work, the effect of the mass of the cluster projectiles on the process was analyzed. The launched clusters were formed by different types of charged atoms: He, Ne, Ar, Kr, and Xe. Due to the different collision processes, the formed surface patterns stand out more if the mass of the projectile atoms is greater, regardless of the angle of incidence of the clusters. Two processes control the morphological evolution of the surface during the bombardment phase: sputtering erosion and surface atomic redistribution. At grazing angles, the contribution of sputtering is greater during the process. In fact, heavier species give greater sputtering, and the redistribution factor becomes lower. The weight of redistribution is greater for intermediate angles above the critical angle (50° and 60°), since the displacement is greater for heavier species, and the redistribution factor takes substantially higher values. The experimental results point to a shift in the critical angle with the mass of the projectile atom. In the case of He, a very light ion, the results are marked by channeling and vertical displacements.

Keywords

• sputtering
• pattern formation
• cluster beam
• molecular dynamics