DISORDERING AND DEFECT PRODUCTION IN SILICON BY KEV ION IRRADIATION STUDIED BY MOLECULAR-DYNAMICS

We discuss the use of molecular dynamics simulation methods to study d isordering and ion implantation in silicon. We discuss the simulation methodology and introduce the interatomic potential employed, with a c ritical discussion of its applicability. We show that in silicon the d isplacement cascade results in a distinct primary state of damage domi nated by large pockets of highly unrelaxed amorphous-like disordered s ilicon. The amorphous volume produced for 5 keV Si on Si cascades cont ains approximate to 1000 atoms, corresponding to an energy cost of app roximately 10 eV/atom. Replacement collision sequences are found to be very short in silicon and as a result, very few point defects appear as a consequence of the displacement cascade. We show that upon anneal ing of the damage microstructure at high temperature, the amorphous po ckets recrystallize and result in the freezing-in in the lattice of va cancies, SIAs and their clusters. We discuss the effect of the ion mas s on defect production and amorphization, and present results on the t emperature dependence of the damage as well on the stability of the da mage clusters for boron and arsenic cascades.