Mechanisms of cluster implantation in silicon: A molecular-dynamics study

Employing molecular dynamics, we have simulated collisions of various sizes of 5.7-keV silicon clusters with a silicon surface. At this energy, the simulation provides an atomistic description of the evolution of the multiple scattering process of atoms in the cluster as well as the substrate where atoms interact with each other by covalent forces. The change from the collision cascade that is characteristic in the single-ion case to the simultaneous collision process that leads to the collective motion of particles, such as macroscopic vibration of the surface and shock waves, is found by increasing the number of the atoms in the cluster. With an increase in cluster size, the impurity profile and the damaged region for the cluster ion implantation is also found to be shallower. In contrast to single-ion implantation, cluster implantation may not induce defects in deep regions, making it suitable for device design. The channeling effect is found to be mainly suppressed by the low-frequency macroscopic vibrations of the surface rather than by the amorphization of the surface caused by the impact. [S0163-1829(98)03136-1].