MODEL FOR AMORPHIZATION PROCESSES IN ION-IMPLANTED SI

A model for amorphization processes in ion-implanted Si has been proposed, in which a divacancy and di-interstitial (D-D) pair introduced in the crystalline Si lattice give rise to a local atomic arrangement including five- and seven-member rings. Stable atomic configurations were determined in super-cells of 216 Si atoms, including randomly distributed D-D pairs, by employing the Tersoff potential for the interatomic force calculations. Based on the proposed model, radial distribution functions, bond-angle distribution, and phonon densities of states were calculated as functions of the number of the D-D pairs and it was found that complete amorphization starts to occur when the number of D-D pairs per atom exceeds approximately 0.2 or approximately 2 D-D pairs are formed in the fcc cubic lattice.