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S.T. Nakagawa, M. Iwatani, G. Betz:
"A Coalescence Mechanism of Impurity Atoms Implanted into a Crystalline Target at Low Temperatures";
Journal of the Physical Society of Japan, 75 (2006), 0246021 - 0246025.

We have studied the coalescence mechanism of impurity atoms implanted into a crystalline target at

low temperatures, paying attention to the dimer formation mechanism. A classical molecular-dynamics

(MD) calculations was used in the case of 1 keV B ion implantation at 100K into a crystalline silicon

(c-Si) target that was supersaturated with pre-embedded B atoms at a concentration of 3 at. %. The initial

phase of dimer formation was investigated in terms of the temperature distribution and the degradation of

the long-range order (LRO) parameters defined in the pixel mapping (PM) method. One result was the

locally high temperature and big temperature gradient that revealed the acceleration of collisional

diffusion of light impurity atoms in the host medium. The other finding was the decrease of the LRO

parameters. This fact associated with the number of self-interstitial atoms (SIAs) implies a deformed

potential-field in a crystal under ion irradiation. These results indicate that dynamically enhanced

diffusion or collisional-diffusion is the origin of dimer formation.

KEYWORDS: molecular dynamics, B cluster, nanoparticle formation, silicon, collisional diffusion

DOI: 10.1143/JPSJ.75.024602

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