A molecular dynamics study of defect production due to low-energy collisions

Molecular dynamics (MD) simulations of collision cascades were studied in o rder to understand the effect of energy, temperature and direction of the p rimary knock-on atom (PKA) on the defect production in single crystal silic on for low-energy collision events. MD simulations were performed with ion energies ranging from 100 eV to 1 keV where the PKA was directed along the three major crystallographic directions at 0, 300 and 600 K. Collision casc ades resulting from PKA energies above 100 eV appeared to undergo a solid- to liquid-like transformation at the height of the cascade event. Upon cool ing, the liquid-like regions collapse resulting in the formation of numerou s isolated defects and clusters of defects. We found that bulb and near-sur face collision events followed the modified Kinchin-Pease model for defect production in silicon for the energies studied. Minimal temperature depende nce was found for collision events that occurred in the bulk of the silicon crystal within the first 10 ps of the simulation.