Nucleation process during excimer laser annealing of amorphous silicon thin films on glass: A molecular-dynamics study

We have performed molecular-dynamics simulations of heating, melting and recrystallization processes in amorphous silicon (a-Si) thin films deposited on glass during excimer laser annealing. By partially heating the a-Si surface region with 2 nm depth and removing the thermal energy from the bottom of the glass substrate, a steady-state temperature profile was obtained in the a-Si layer with the thickness of 15 nm and only the surface region was melted. It was found that the nucleation predominantly occurred in the a-Si region as judged by the coordination numbers and diffusion constants of atoms in the region. The results suggest that the nucleation occurs in the unmelted residual a-Si region during the laser irradiation and then the crystal growth proceeds toward liquid Si region under the near-complete melting condition.