Behavior of impurity atoms during crystal growth from melted silicon: Carbon atoms

We have investigated the behavior of carbon (C) atoms during the crystal growth from liquid silicon (Si) based on molecular-dynamics simulations using the Tersoff interatomic potential. From the analyses of the pair-correlation functions, distribution of local coordination numbers, and bond angle distributions, it was found that C atoms in melted Si have a preference for three- and four-fold sites corresponding to the sp² and sp³ bondings, respectively, while C atoms in crystalline Si grown from the melt occupy the substitutional sites. Crystal growth in the [0 0 1] direction occurred by attaching Si atoms in melt at kink sites associated with {1 1 1} facets formed at the solid-liquid interface. On the other hand, the interface was smooth and layer-by-layer growth occurred in the [1 1 1] direction. It has been also shown that the aggregation of C atoms can induce defects. These defects were localized around the C atoms in the case of the [0 0 1] growth, while they developed with the [1 1 1] crystal growth. This was attributed to a remarkable difference between the (0 0 1) and (1 1 1) solid-liquid Si interface structures.