A Coalescence Mechanism of Impurity Atoms Implanted into a Crystalline Target at Low Temperatures

Abstract

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 100 K 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.