Molecular dynamics simulation of low-energy collision cascades and atomic mixing in silicon

Abstract We investigate atomic relocation processes in silicon at OK, initiated by an internal 100eV silicon recoil. The molecular dynamics code MODYSEM is used, based on a Tersoff potential for silicon. A fitting procedure was used for the generation of 8 potential valid over the whole energy range of interest. The contribution of the collisional, spontaneous relaxation and thermalization stages to the atomic relocation process are discussed. A threshold distance for the definition of relocated atoms is determined, which separates atomic displacements into stable and unstable (or transient) groups. The atomic mixing process is quantified in terms of the first and second spatial moments over the relocation cross-section. These moments depend on the criterion used to define a relocated Si atom, with short-distance thermal-like atomic displacements, which appear during the thermalization stage, dominating the values of the spatial moments. However, the moments of the relocation cross-section calculated by considering only the stable displacements are generated mainly by collisional atomic relocations.

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