DEFECT PRODUCTION AND ANNEALING KINETICS IN ELEMENTAL METALS AND SEMICONDUCTORS

We present a review of recent results of molecular dynamics (MD) and k inetic Monte Carlo (KMC) simulations of defect production and annealin g in irradiated metals and semiconductors. The MD simulations describe the primary damage state in elemental metals Fe, V and Au, and in an elemental semiconductor Si. We describe the production of interstitial and vacancy clusters in the cascades and highlight the differences am ong the various materials. In particular, we discuss how covalent bond ing in Si affects defect production and amorphization resulting in a v ery different primary damage state from the metals. We also use MD sim ulations to extract prefactors and activation energies for migration o f point defects, as well as to investigate the energetics, geometry an d diffusivity of small vacancy and interstitial clusters. We show that , in the metals, small interstitial clusters are highly mobile and gli de in one dimension along the direction of the Burger's vector. In sil icon, we show that, in contrast to the metals, the neutral vacancy dif fuses faster than the neutral self-interstitial. The results for the p rimary damage state and for the defect energetics and kinetics are the n combined and used in a kinetic Monte Carlo simulation to investigate the escape efficiency of defects from their nascent cascade in metals , and the effect of dose rate on damage accumulation and amorphization in silicon. We show that in fee metals Au and Pb at or above stage V the escape probability is approximately 40% for 30 keV recoils so that the freely migrating defect fraction is approximately 10% of the dpa standard. In silicon, we show that damage accumulation at room tempera ture during light ion implantation can be significantly reduced by dec reasing the dose rate. The results are compared to scanning tunneling microscopy experiments. (C) 1997 Published by Elsevier Science B.V.