Complex crater formation on silicon surfaces by low-energy Arn+ cluster ion implantation

Silicon samples were implanted by small mass-selected Arn+ cluster and Ar+ monomer ions with energies in the range of 1.5–18.0 keV/ion. Atomic force microscopy (AFM) shows simple and complex crater formation on the Si surface at the collision spots. A typical complex crater is surrounded by a low-height (∼0.5 nm) rim and it encloses a centre-positioned cone-shaped hillock with height of up to 3.5 nm depending on the implantation conditions. The morphology and dimensions of the craters and hillocks are studied as a function of the cluster size and implantation energy. A model explaining the hillock formation with relation to the thermal-transfer effect and local target melting at the collision spot is proposed.