Surface erosion under cluster ion implantation: crater and hillock formation

Abstract

Silicon samples implanted by small mass-selected Arn* and (N2)n* cluster ions with energies in the range of 3-18 keV/cluster are studied using atomic force microscopy. Control samples implanted by Ar* ions with the energies of 1.5-5.0 keV are used for comparison. The images show surface erosion appearing as simple and complex crater formation in the cases of both monomer and cluster bombardment. The complex craters with centre-positioned cone-shaped hillocks are surrounded by low-height rims (-0.5 nm). The hillock height varies on a few nm scale depending on the implantation energy, cluster size and species. A simple model explaining the hillock formation with relation to the thermal-transfer effect at the collision spot is proposed.