Molecular dynamics simulations for amorphous/crystalline Si interface: Amorphization and crystallization induced by simple defects

Molecular dynamics calculations have been performed to simulate ion-beam-induced epitaxial crystallization (IBIEC) and interfacial amorphization (IBIIA) at an amorphous/crystalline (a/c) Si interface based on the ordinary Langevin equation employing the Tersoff potential for Si. Half part of the c-Si lattice composed of 216 atoms was amorphized by accumulating divacancy and di-interstitial (D-D) pairs and a/c interfaces were formed. Simple defects such as single vacancies and divacancies were introduced at the a/c interfaces and atomistic simulations were carried out. Neither IBIEC nor IBIIA were observed by introducing only vacancy-type defects. On the other hand, a D-D pair was found to give rise to both amorphization and crystallization. These results suggest that IBIEC and IBIIA can be described as a bond-switching process between the 6-member and 5- or 7-member rings which can be induced by a D-D pair formation at the a/c interface.