Properties of polycrystals and nanotwinned structures in silicon during rapid cooling process

The evolution characteristics of polycrystals and nano-twinned structures during the rapid solidification of silicon under cooling rate of 1010 K s(-1) are investigated based on molecular dynamics simulation. The microstructural properties of silicon were analyzed by several structural characterization methods. The distorted tetrahedral units with 5 nearest-neighbor atoms play different roles in three stages of the quenching process. As transitional structures, they play a significant part in liquid to liquid and liquid to crystal transition, and break the translational symmetry of the crystalline structures. The tetrahedral units can aggregate to form polycrystals with high stability in this system. When the temperature was decreased at a cooling rate of 1010 K s(-1), Coherent twin boundaries, having excellent structural stability and configurational continuity, were easily formed between zinc-blende and wurtzite structures.