Classical MD study on the the mobility of di- and tri-interstitials

In a recent work [1], a combined simulation method was applied to investigate ion-beam-induced defect formation in silicon. BCA simulations were used to treat the ballistic processes, whereas the subsequent fast relaxation and the first stage of thermally activated processes were described by classical MD calculations. It was found that the metastable defect structure formed immediately after ion impact consists not only of isolated vacancies and self-interstitials but also of complex defects. A more detailed analysis of the results shows, that at elevated implantation temperatures or during the annealing of the defect structures obtained at room temperature, di- and tri-interstitials are formed. In some cases a high mobility of these defects is observed. In agreement with former studies [2,3], the di-interstital is found to move relatively fast. The present contribution deals with systematic investigations on the migration of di- and tri-interstitials. The classical MD simulations allow direct investigations of the motion of defects and its atomic mechanisms. Particular attention is paid to the role of transformations between different modifications of di- or tri-interstitials. These transformations may lead to an substantial increase or decrease of the defect mobility. The present results are compared with the few literature data obtained by tight-binding and density-functional methods which employ mainly static potential energy calculations.
[1] M. Posselt, Mat. Res. Soc. Symp. Proc. 647 (2001) O2.1.1.
[2] G. H. Gilmer, T. Diaz de la Rubia, D. M. Stock, M. Jaraiz, Nucl. Instr. Meth. Phys. Res. B 102 (1995) 247.
[3] M. Hane, T. Ikezawa, G. H. Gilmer, Proc. SISPAD 2000, IEEE Catalog Number 00TH8502, p. 119 , IEEE, Piscataway, 2000.